diff --git a/DEPS b/DEPS
index 32a48b1c53a..76095eb3ad9 100644
--- a/DEPS
+++ b/DEPS
@@ -144,7 +144,7 @@ vars = {
   "pub_rev": "3c14d86a67db7207bbc9f654ac49ee60e08e5240",
   "pub_semver_rev": "f50d80ef10c4b2fa5f4c8878036a4d9342c0cc82",
   "resource_rev": "6b79867d0becf5395e5819a75720963b8298e9a7",
-  "root_certificates_rev": "ef7b563890e219a93579b61584f9ffa64c7c8d9c",
+  "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",
   "rust_revision": "b7856f695d65a8ebc846754f97d15814bcb1c244",
   "shelf_static_rev": "fa30419055279a00c9e428439b1abe362d18f25d",
   "shelf_packages_handler_rev": "78302e67c035047e6348e692b0c1182131f0fe35",
diff --git a/runtime/BUILD.gn b/runtime/BUILD.gn
index bc878338a3f..30166786bc6 100644
--- a/runtime/BUILD.gn
+++ b/runtime/BUILD.gn
@@ -71,22 +71,22 @@ config("dart_os_config") {
   defines = []
 
   if (target_os == "android") {
-    defines += [ "TARGET_OS_ANDROID" ]
+    defines += [ "DART_TARGET_OS_ANDROID" ]
   } else if (target_os == "fuchsia") {
-    defines += [ "TARGET_OS_FUCHSIA" ]
+    defines += [ "DART_TARGET_OS_FUCHSIA" ]
   } else if (target_os == "ios") {
-    defines += [ "TARGET_OS_MACOS" ]
-    defines += [ "TARGET_OS_MACOS_IOS" ]
+    defines += [ "DART_TARGET_OS_MACOS" ]
+    defines += [ "DART_TARGET_OS_MACOS_IOS" ]
   } else if (target_os == "linux") {
-    defines += [ "TARGET_OS_LINUX" ]
+    defines += [ "DART_TARGET_OS_LINUX" ]
   } else if (target_os == "mac") {
-    defines += [ "TARGET_OS_MACOS" ]
+    defines += [ "DART_TARGET_OS_MACOS" ]
   } else if (target_os == "win") {
-    defines += [ "TARGET_OS_WINDOWS" ]
+    defines += [ "DART_TARGET_OS_WINDOWS" ]
   } else if (target_os == "winuwp") {
     defines += [
-      "TARGET_OS_WINDOWS",
-      "TARGET_OS_WINDOWS_UWP",
+      "DART_TARGET_OS_WINDOWS",
+      "DART_TARGET_OS_WINDOWS_UWP",
     ]
   } else {
     print("Unknown target_os: $target_os")
@@ -98,7 +98,7 @@ config("dart_os_config") {
 # targeting Mac and Linux. This configuration is used to unconditionally target
 # Fuchsia. It should not be combined with dart_os_config.
 config("dart_os_fuchsia_config") {
-  defines = [ "TARGET_OS_FUCHSIA" ]
+  defines = [ "DART_TARGET_OS_FUCHSIA" ]
 }
 
 config("dart_arch_config") {
diff --git a/runtime/bin/abstract_socket_test.cc b/runtime/bin/abstract_socket_test.cc
index 7af06b61a20..fab2f26fe49 100644
--- a/runtime/bin/abstract_socket_test.cc
+++ b/runtime/bin/abstract_socket_test.cc
@@ -8,7 +8,7 @@
 // closes the connection and UNIX socket.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -101,4 +101,4 @@ int main() {
   return -1;
 }
 
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/address_sanitizer.cc b/runtime/bin/address_sanitizer.cc
index 708e1690b14..a780894b7eb 100644
--- a/runtime/bin/address_sanitizer.cc
+++ b/runtime/bin/address_sanitizer.cc
@@ -4,7 +4,7 @@
 
 #include "platform/globals.h"
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOSX)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOSX)
 #if defined(__has_feature)
 #if __has_feature(address_sanitizer)
 
@@ -23,4 +23,4 @@ __asan_default_options() {
 
 #endif  // __has_feature(address_sanitizer)
 #endif  // defined(__has_feature)
-#endif  //  defined(HOST_OS_LINUX) || defined(HOST_OS_MACOSX)
+#endif  //  defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOSX)
diff --git a/runtime/bin/console_posix.cc b/runtime/bin/console_posix.cc
index af28e153e6c..17116da2337 100644
--- a/runtime/bin/console_posix.cc
+++ b/runtime/bin/console_posix.cc
@@ -3,8 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                        \
-    defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/console.h"
 
@@ -88,5 +88,5 @@ void Console::RestoreConfig() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||
-        // defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||       \
+        // defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/console_win.cc b/runtime/bin/console_win.cc
index 6d7511abaad..59e6603f32c 100644
--- a/runtime/bin/console_win.cc
+++ b/runtime/bin/console_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #include "bin/console.h"
 
 #include "bin/file.h"
@@ -152,4 +152,4 @@ void Console::RestoreConfig() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/crashpad.cc b/runtime/bin/crashpad.cc
index 18ed3f53895..d6d900cc7b3 100644
--- a/runtime/bin/crashpad.cc
+++ b/runtime/bin/crashpad.cc
@@ -21,7 +21,7 @@ namespace dart {
 namespace bin {
 
 #if defined(DART_USE_CRASHPAD)
-#if !defined(HOST_OS_WINDOWS)
+#if !defined(DART_HOST_OS_WINDOWS)
 #error "Currently we only support Crashpad on Windows"
 #endif
 
diff --git a/runtime/bin/crypto_android.cc b/runtime/bin/crypto_android.cc
index 6db66ebdff2..f8b1a9f7366 100644
--- a/runtime/bin/crypto_android.cc
+++ b/runtime/bin/crypto_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include <errno.h>  // NOLINT
 #include <fcntl.h>  // NOLINT
@@ -41,4 +41,4 @@ bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/crypto_fuchsia.cc b/runtime/bin/crypto_fuchsia.cc
index c2fe425aa2f..a4623fea50c 100644
--- a/runtime/bin/crypto_fuchsia.cc
+++ b/runtime/bin/crypto_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/crypto.h"
 
@@ -20,4 +20,4 @@ bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/crypto_linux.cc b/runtime/bin/crypto_linux.cc
index d3af9e0e895..957578e08f7 100644
--- a/runtime/bin/crypto_linux.cc
+++ b/runtime/bin/crypto_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include <errno.h>  // NOLINT
 #include <fcntl.h>  // NOLINT
@@ -41,4 +41,4 @@ bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/crypto_macos.cc b/runtime/bin/crypto_macos.cc
index b3afc6fe63c..24dfe9bd896 100644
--- a/runtime/bin/crypto_macos.cc
+++ b/runtime/bin/crypto_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include <errno.h>  // NOLINT
 #include <fcntl.h>  // NOLINT
@@ -39,4 +39,4 @@ bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/crypto_win.cc b/runtime/bin/crypto_win.cc
index 4233e980132..fe72659f49f 100644
--- a/runtime/bin/crypto_win.cc
+++ b/runtime/bin/crypto_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include <bcrypt.h>
 #include "bin/crypto.h"
@@ -28,4 +28,4 @@ bool Crypto::GetRandomBytes(intptr_t count, uint8_t* buffer) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index 72893415d3d..9f60f2a4b6c 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -59,11 +59,11 @@ MagicNumberData kernel_list_magic_number = {
 MagicNumberData gzip_magic_number = {2, {0x1f, 0x8b, 0, 0}};
 
 static bool IsWindowsHost() {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   return true;
-#else   // defined(HOST_OS_WINDOWS)
+#else   // defined(DART_HOST_OS_WINDOWS)
   return false;
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
 }
 
 Dart_Handle CommandLineOptions::CreateRuntimeOptions() {
diff --git a/runtime/bin/dfe.cc b/runtime/bin/dfe.cc
index be5c2494118..a5710f148f2 100644
--- a/runtime/bin/dfe.cc
+++ b/runtime/bin/dfe.cc
@@ -140,7 +140,7 @@ bool DFE::CanUseDartFrontend() const {
 }
 
 PathSanitizer::PathSanitizer(const char* path) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   // For Windows we need to massage the paths a bit according to
   // http://blogs.msdn.com/b/ie/archive/2006/12/06/file-uris-in-windows.aspx
   //
@@ -169,15 +169,15 @@ PathSanitizer::PathSanitizer(const char* path) {
   sanitized_uri_ = std::unique_ptr<char[]>(uri);
 #else
   sanitized_uri_ = path;
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
 }
 
 const char* PathSanitizer::sanitized_uri() const {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   return sanitized_uri_.get();
 #else
   return sanitized_uri_;
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
 }
 
 Dart_KernelCompilationResult DFE::CompileScript(const char* script_uri,
diff --git a/runtime/bin/dfe.h b/runtime/bin/dfe.h
index b381f9c5819..649cc321b11 100644
--- a/runtime/bin/dfe.h
+++ b/runtime/bin/dfe.h
@@ -138,11 +138,11 @@ class PathSanitizer {
   const char* sanitized_uri() const;
 
  private:
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   std::unique_ptr<char[]> sanitized_uri_;
 #else
   const char* sanitized_uri_;
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
 
   DISALLOW_COPY_AND_ASSIGN(PathSanitizer);
 };
diff --git a/runtime/bin/directory_android.cc b/runtime/bin/directory_android.cc
index 67e47dfb5a8..27e0f0156d3 100644
--- a/runtime/bin/directory_android.cc
+++ b/runtime/bin/directory_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/directory.h"
 
@@ -508,4 +508,4 @@ bool Directory::Rename(Namespace* namespc,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/directory_fuchsia.cc b/runtime/bin/directory_fuchsia.cc
index 4cbffbe2ae7..d37394a70b2 100644
--- a/runtime/bin/directory_fuchsia.cc
+++ b/runtime/bin/directory_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/directory.h"
 
@@ -512,4 +512,4 @@ bool Directory::Rename(Namespace* namespc,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/directory_linux.cc b/runtime/bin/directory_linux.cc
index 5321a9a4afe..a1065e3b7a6 100644
--- a/runtime/bin/directory_linux.cc
+++ b/runtime/bin/directory_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/directory.h"
 
@@ -506,4 +506,4 @@ bool Directory::Rename(Namespace* namespc,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/directory_macos.cc b/runtime/bin/directory_macos.cc
index 7a884e92e0f..cce21549053 100644
--- a/runtime/bin/directory_macos.cc
+++ b/runtime/bin/directory_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/directory.h"
 
@@ -446,4 +446,4 @@ bool Directory::Rename(Namespace* namespc,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/directory_win.cc b/runtime/bin/directory_win.cc
index 16b09846da3..804bfff7309 100644
--- a/runtime/bin/directory_win.cc
+++ b/runtime/bin/directory_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/directory.h"
 
@@ -531,4 +531,4 @@ bool Directory::Rename(Namespace* namespc,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/elf_loader.cc b/runtime/bin/elf_loader.cc
index 22c2cbc8d3a..92d66857a2d 100644
--- a/runtime/bin/elf_loader.cc
+++ b/runtime/bin/elf_loader.cc
@@ -10,7 +10,7 @@
 #include <vm/cpu.h>
 #include <vm/virtual_memory.h>
 
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 #include <sys/mman.h>
 #endif
 
@@ -25,7 +25,7 @@ namespace elf {
 class Mappable {
  public:
   static Mappable* FromPath(const char* path);
-#if defined(HOST_OS_FUCHSIA) || defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_FUCHSIA) || defined(DART_HOST_OS_LINUX)
   static Mappable* FromFD(int fd);
 #endif
   static Mappable* FromMemory(const uint8_t* memory, size_t size);
@@ -151,7 +151,7 @@ Mappable* Mappable::FromPath(const char* path) {
   return new FileMappable(File::Open(/*namespc=*/nullptr, path, File::kRead));
 }
 
-#if defined(HOST_OS_FUCHSIA) || defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_FUCHSIA) || defined(DART_HOST_OS_LINUX)
 Mappable* Mappable::FromFD(int fd) {
   return new FileMappable(File::OpenFD(fd));
 }
@@ -424,7 +424,7 @@ bool LoadedElf::LoadSegments() {
       ERROR("Unsupported segment flag set.");
     }
 
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
     // mmap is less flexible on Fuchsia than on Linux and Darwin, in (at least)
     // two important ways:
     //
@@ -546,7 +546,7 @@ MappedMemory* LoadedElf::MapFilePiece(uword file_start,
 
 using namespace dart::bin::elf;  // NOLINT
 
-#if defined(HOST_OS_FUCHSIA) || defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_FUCHSIA) || defined(DART_HOST_OS_LINUX)
 DART_EXPORT Dart_LoadedElf* Dart_LoadELF_Fd(int fd,
                                             uint64_t file_offset,
                                             const char** error,
@@ -569,7 +569,7 @@ DART_EXPORT Dart_LoadedElf* Dart_LoadELF_Fd(int fd,
 }
 #endif
 
-#if !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_FUCHSIA)
 DART_EXPORT Dart_LoadedElf* Dart_LoadELF(const char* filename,
                                          uint64_t file_offset,
                                          const char** error,
diff --git a/runtime/bin/entrypoints_verification_test_extension_dllmain_win.cc b/runtime/bin/entrypoints_verification_test_extension_dllmain_win.cc
index cbf42d53bee..8ff69eef67e 100644
--- a/runtime/bin/entrypoints_verification_test_extension_dllmain_win.cc
+++ b/runtime/bin/entrypoints_verification_test_extension_dllmain_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>  // NOLINT
@@ -12,4 +12,4 @@ BOOL APIENTRY DllMain(HMODULE module, DWORD reason, LPVOID reserved) {
   return true;
 }
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/eventhandler.h b/runtime/bin/eventhandler.h
index b45deac7ea2..c6c86861015 100644
--- a/runtime/bin/eventhandler.h
+++ b/runtime/bin/eventhandler.h
@@ -582,15 +582,15 @@ class DescriptorInfoMultipleMixin : public DI {
 }  // namespace dart
 
 // The event handler delegation class is OS specific.
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 #include "bin/eventhandler_android.h"
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
 #include "bin/eventhandler_fuchsia.h"
-#elif defined(HOST_OS_LINUX)
+#elif defined(DART_HOST_OS_LINUX)
 #include "bin/eventhandler_linux.h"
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include "bin/eventhandler_macos.h"
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 #include "bin/eventhandler_win.h"
 #else
 #error Unknown target os.
diff --git a/runtime/bin/eventhandler_android.cc b/runtime/bin/eventhandler_android.cc
index 958e5c3766f..b6dfc170f25 100644
--- a/runtime/bin/eventhandler_android.cc
+++ b/runtime/bin/eventhandler_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/eventhandler.h"
 #include "bin/eventhandler_android.h"
@@ -432,4 +432,4 @@ uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/eventhandler_fuchsia.cc b/runtime/bin/eventhandler_fuchsia.cc
index f15bc3befa6..1f14ffbc5d1 100644
--- a/runtime/bin/eventhandler_fuchsia.cc
+++ b/runtime/bin/eventhandler_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/eventhandler.h"
 #include "bin/eventhandler_fuchsia.h"
@@ -659,4 +659,4 @@ uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/eventhandler_linux.cc b/runtime/bin/eventhandler_linux.cc
index 48ef4ef3e00..ac9deb53bcd 100644
--- a/runtime/bin/eventhandler_linux.cc
+++ b/runtime/bin/eventhandler_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/eventhandler.h"
 #include "bin/eventhandler_linux.h"
@@ -436,4 +436,4 @@ uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/eventhandler_macos.cc b/runtime/bin/eventhandler_macos.cc
index 904ae0afc8d..ee8f0fb1394 100644
--- a/runtime/bin/eventhandler_macos.cc
+++ b/runtime/bin/eventhandler_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/eventhandler.h"
 #include "bin/eventhandler_macos.h"
@@ -496,4 +496,4 @@ uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/eventhandler_win.cc b/runtime/bin/eventhandler_win.cc
index 0de689a3c37..abdba9a6ad0 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/eventhandler.h"
 #include "bin/eventhandler_win.h"
@@ -1499,4 +1499,4 @@ void EventHandlerImplementation::Shutdown() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/exe_utils.cc b/runtime/bin/exe_utils.cc
index 22f79864c3c..606646574c5 100644
--- a/runtime/bin/exe_utils.cc
+++ b/runtime/bin/exe_utils.cc
@@ -16,11 +16,11 @@ static bool StartsWithPathSeparator(const char* path,
                                     const char* sep,
                                     intptr_t sep_length) {
   return (strncmp(path, sep, sep_length) == 0
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
           // TODO(aam): GetExecutableName doesn't work reliably on Windows,
           || *path == '/'
 #endif
-  );
+  );  // NOLINT
 }
 
 // Returns the directory portion of a given path.
diff --git a/runtime/bin/extensions_android.cc b/runtime/bin/extensions_android.cc
index 32c32a7d026..f8f153b4c55 100644
--- a/runtime/bin/extensions_android.cc
+++ b/runtime/bin/extensions_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include <dlfcn.h>  // NOLINT
 #include "bin/extensions.h"
@@ -39,4 +39,4 @@ Dart_Handle Extensions::GetError() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/extensions_fuchsia.cc b/runtime/bin/extensions_fuchsia.cc
index de71763bc11..637533a4dbe 100644
--- a/runtime/bin/extensions_fuchsia.cc
+++ b/runtime/bin/extensions_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/extensions.h"
 
@@ -43,4 +43,4 @@ Dart_Handle Extensions::GetError() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/extensions_linux.cc b/runtime/bin/extensions_linux.cc
index e2359d02dbc..d0f3d0f1418 100644
--- a/runtime/bin/extensions_linux.cc
+++ b/runtime/bin/extensions_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include <dlfcn.h>  // NOLINT
 #include "bin/extensions.h"
@@ -39,4 +39,4 @@ Dart_Handle Extensions::GetError() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/extensions_macos.cc b/runtime/bin/extensions_macos.cc
index f5436a0c2df..b5be6778608 100644
--- a/runtime/bin/extensions_macos.cc
+++ b/runtime/bin/extensions_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include <dlfcn.h>  // NOLINT
 #include "bin/extensions.h"
@@ -39,4 +39,4 @@ Dart_Handle Extensions::GetError() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/extensions_win.cc b/runtime/bin/extensions_win.cc
index 23b4349cd3b..d17d84382e3 100644
--- a/runtime/bin/extensions_win.cc
+++ b/runtime/bin/extensions_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/extensions.h"
 #include "bin/utils.h"
@@ -51,4 +51,4 @@ Dart_Handle Extensions::GetError() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/fdutils_android.cc b/runtime/bin/fdutils_android.cc
index de1fb6b6711..ad30d28ff99 100644
--- a/runtime/bin/fdutils_android.cc
+++ b/runtime/bin/fdutils_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/fdutils.h"
 
@@ -139,4 +139,4 @@ void FDUtils::SaveErrorAndClose(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/fdutils_fuchsia.cc b/runtime/bin/fdutils_fuchsia.cc
index eb40c73a75d..f62e66c135c 100644
--- a/runtime/bin/fdutils_fuchsia.cc
+++ b/runtime/bin/fdutils_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/fdutils.h"
 
@@ -138,4 +138,4 @@ void FDUtils::SaveErrorAndClose(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/fdutils_linux.cc b/runtime/bin/fdutils_linux.cc
index 1caa7863466..f730ea6c595 100644
--- a/runtime/bin/fdutils_linux.cc
+++ b/runtime/bin/fdutils_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/fdutils.h"
 
@@ -139,4 +139,4 @@ void FDUtils::SaveErrorAndClose(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/fdutils_macos.cc b/runtime/bin/fdutils_macos.cc
index 341e85fc9bc..a7b90e3e025 100644
--- a/runtime/bin/fdutils_macos.cc
+++ b/runtime/bin/fdutils_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/fdutils.h"
 
@@ -139,4 +139,4 @@ void FDUtils::SaveErrorAndClose(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc b/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
index 8564aa69235..a4ad2d55e75 100644
--- a/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
+++ b/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
@@ -11,7 +11,7 @@
 
 #include "platform/globals.h"
 #include "platform/memory_sanitizer.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #include <psapi.h>
 #include <windows.h>
 #else
@@ -116,7 +116,7 @@ DART_EXPORT uint8_t IsThreadInGenerated() {
              : 0;
 }
 
-#if !defined(HOST_OS_WINDOWS)
+#if !defined(DART_HOST_OS_WINDOWS)
 DART_EXPORT void* UnprotectCodeOtherThread(void* isolate,
                                            std::condition_variable* var,
                                            std::mutex* mut) {
@@ -185,7 +185,7 @@ DART_EXPORT void* TestUnprotectCode(void (*fn)(void)) {
 // Clobbers some registers with special meaning in Dart before re-entry, for
 // stress-testing. Not used on 32-bit Windows due to complications with Windows
 // "safeseh".
-#if defined(TARGET_OS_WINDOWS) && defined(HOST_ARCH_IA32)
+#if defined(DART_TARGET_OS_WINDOWS) && defined(HOST_ARCH_IA32)
 void ClobberAndCall(void (*fn)()) {
   fn();
 }
@@ -203,7 +203,7 @@ struct CallbackTestData {
   void (*callback)();
 };
 
-#if defined(TARGET_OS_LINUX)
+#if defined(DART_TARGET_OS_LINUX)
 
 thread_local sigjmp_buf buf;
 void CallbackTestSignalHandler(int) {
@@ -312,13 +312,13 @@ DART_EXPORT intptr_t TestLeafCallApi(void (*fn)()) {
 #endif
 }
 
-#endif  // defined(TARGET_OS_LINUX)
+#endif  // defined(DART_TARGET_OS_LINUX)
 
 // Restore default SIGPIPE handler, which is only needed on mac
 // since that is the only platform we explicitly ignore it.
 // See Platform::Initialize() in platform_macos.cc.
 DART_EXPORT void RestoreSIGPIPEHandler() {
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
   signal(SIGPIPE, SIG_DFL);
 #endif
 }
@@ -428,7 +428,7 @@ void Fatal(char const* file, int line, char const* error) {
 #define FATAL(error) Fatal(__FILE__, __LINE__, error)
 
 DART_EXPORT void SleepOnAnyOS(intptr_t seconds) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   Sleep(1000 * seconds);
 #else
   sleep(seconds);
diff --git a/runtime/bin/ffi_unit_test/BUILD.gn b/runtime/bin/ffi_unit_test/BUILD.gn
index 2a7b371c387..99396af56e9 100644
--- a/runtime/bin/ffi_unit_test/BUILD.gn
+++ b/runtime/bin/ffi_unit_test/BUILD.gn
@@ -50,25 +50,23 @@ config("define_target_arch_x64") {
 }
 
 config("define_target_os_android") {
-  defines = [ "TARGET_OS_ANDROID" ]
+  defines = [ "DART_TARGET_OS_ANDROID" ]
 }
 
 config("define_target_os_ios") {
-  # This is TARGET_OS_MACOS_IOS instead of TARGET_OS_IOS because the latter is
-  # defined by Xcode already. See https://dartbug.com/24453.
-  defines = [ "TARGET_OS_MACOS_IOS" ]
+  defines = [ "DART_TARGET_OS_MACOS_IOS" ]
 }
 
 config("define_target_os_linux") {
-  defines = [ "TARGET_OS_LINUX" ]
+  defines = [ "DART_TARGET_OS_LINUX" ]
 }
 
 config("define_target_os_macos") {
-  defines = [ "TARGET_OS_MACOS" ]
+  defines = [ "DART_TARGET_OS_MACOS" ]
 }
 
 config("define_target_os_windows") {
-  defines = [ "TARGET_OS_WINDOWS" ]
+  defines = [ "DART_TARGET_OS_WINDOWS" ]
 }
 
 build_run_ffi_unit_tests("run_ffi_unit_tests_arm_android") {
diff --git a/runtime/bin/file.h b/runtime/bin/file.h
index 98d374840a2..edeb38873c9 100644
--- a/runtime/bin/file.h
+++ b/runtime/bin/file.h
@@ -221,7 +221,7 @@ class File : public ReferenceCounted<File> {
   // (stdin, stout or stderr).
   static File* OpenStdio(int fd);
 
-#if defined(HOST_OS_FUCHSIA) || defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_FUCHSIA) || defined(DART_HOST_OS_LINUX)
   static File* OpenFD(int fd);
 #endif
 
diff --git a/runtime/bin/file_android.cc b/runtime/bin/file_android.cc
index 09902279d7c..b1e9bb04aea 100644
--- a/runtime/bin/file_android.cc
+++ b/runtime/bin/file_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/file.h"
 
@@ -748,4 +748,4 @@ File::Identical File::AreIdentical(Namespace* namespc_1,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/file_fuchsia.cc b/runtime/bin/file_fuchsia.cc
index b466119b8ba..aa7f8821c98 100644
--- a/runtime/bin/file_fuchsia.cc
+++ b/runtime/bin/file_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/file.h"
 
@@ -704,4 +704,4 @@ File::Identical File::AreIdentical(Namespace* namespc_1,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/file_linux.cc b/runtime/bin/file_linux.cc
index 79c084c91d6..625f05447d1 100644
--- a/runtime/bin/file_linux.cc
+++ b/runtime/bin/file_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/file.h"
 
@@ -745,4 +745,4 @@ File::Identical File::AreIdentical(Namespace* namespc_1,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/file_macos.cc b/runtime/bin/file_macos.cc
index fc546c3d976..8fa3cd7c9d3 100644
--- a/runtime/bin/file_macos.cc
+++ b/runtime/bin/file_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/file.h"
 
@@ -650,4 +650,4 @@ File::Identical File::AreIdentical(Namespace* namespc_1,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/file_system_watcher_android.cc b/runtime/bin/file_system_watcher_android.cc
index 0ff4c4229e3..e1634414336 100644
--- a/runtime/bin/file_system_watcher_android.cc
+++ b/runtime/bin/file_system_watcher_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/file_system_watcher.h"
 
@@ -152,4 +152,4 @@ Dart_Handle FileSystemWatcher::ReadEvents(intptr_t id, intptr_t path_id) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/file_system_watcher_fuchsia.cc b/runtime/bin/file_system_watcher_fuchsia.cc
index d898542b607..f6defa22e62 100644
--- a/runtime/bin/file_system_watcher_fuchsia.cc
+++ b/runtime/bin/file_system_watcher_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/file_system_watcher.h"
 
@@ -48,4 +48,4 @@ intptr_t FileSystemWatcher::WatchPath(intptr_t id,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/file_system_watcher_linux.cc b/runtime/bin/file_system_watcher_linux.cc
index fa482906c52..14c18d29165 100644
--- a/runtime/bin/file_system_watcher_linux.cc
+++ b/runtime/bin/file_system_watcher_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/file_system_watcher.h"
 
@@ -146,4 +146,4 @@ Dart_Handle FileSystemWatcher::ReadEvents(intptr_t id, intptr_t path_id) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/file_system_watcher_macos.cc b/runtime/bin/file_system_watcher_macos.cc
index 2cde121b019..1ccf75355e0 100644
--- a/runtime/bin/file_system_watcher_macos.cc
+++ b/runtime/bin/file_system_watcher_macos.cc
@@ -3,11 +3,11 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/file_system_watcher.h"
 
-#if !HOST_OS_IOS
+#if !DART_HOST_OS_IOS
 
 #include <CoreServices/CoreServices.h>  // NOLINT
 #include <errno.h>                      // NOLINT
@@ -350,7 +350,7 @@ Dart_Handle FileSystemWatcher::ReadEvents(intptr_t id, intptr_t path_id) {
 }  // namespace bin
 }  // namespace dart
 
-#else  // !HOST_OS_IOS
+#else  // !DART_HOST_OS_IOS
 
 namespace dart {
 namespace bin {
@@ -387,5 +387,5 @@ intptr_t FileSystemWatcher::WatchPath(intptr_t id,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // !HOST_OS_IOS
-#endif  // defined(HOST_OS_MACOS)
+#endif  // !DART_HOST_OS_IOS
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/file_system_watcher_win.cc b/runtime/bin/file_system_watcher_win.cc
index b37136337e9..3598f51284d 100644
--- a/runtime/bin/file_system_watcher_win.cc
+++ b/runtime/bin/file_system_watcher_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/file_system_watcher.h"
 
@@ -132,4 +132,4 @@ Dart_Handle FileSystemWatcher::ReadEvents(intptr_t id, intptr_t path_id) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/file_win.cc b/runtime/bin/file_win.cc
index 6e11076beec..b7f5dbee115 100644
--- a/runtime/bin/file_win.cc
+++ b/runtime/bin/file_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include <functional>
 #include <memory>
@@ -1128,4 +1128,4 @@ File::Identical File::AreIdentical(Namespace* namespc_1,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/io_buffer.cc b/runtime/bin/io_buffer.cc
index 1d5300530e8..f10e55c37b6 100644
--- a/runtime/bin/io_buffer.cc
+++ b/runtime/bin/io_buffer.cc
@@ -44,7 +44,7 @@ uint8_t* IOBuffer::Reallocate(uint8_t* buffer, intptr_t new_size) {
     }
     return buffer;
   }
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
   // It seems windows realloc() doesn't free memory when shrinking, so we'll
   // manually allocate a new buffer, copy the data and free the old buffer.
   auto new_buffer = IOBuffer::Allocate(new_size);
diff --git a/runtime/bin/main_options.cc b/runtime/bin/main_options.cc
index faf1d5c0d21..108fc9131b4 100644
--- a/runtime/bin/main_options.cc
+++ b/runtime/bin/main_options.cc
@@ -225,13 +225,13 @@ void Options::PrintUsage() {
 "--root-certs-cache=<path>\n"
 "  The path to a cache directory containing the trusted root certificates to\n"
 "  use for secure socket connections.\n"
-#if defined(HOST_OS_LINUX) || \
-    defined(HOST_OS_ANDROID) || \
-    defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_LINUX) || \
+    defined(DART_HOST_OS_ANDROID) || \
+    defined(DART_HOST_OS_FUCHSIA)
 "--namespace=<path>\n"
 "  The path to a directory that dart:io calls will treat as the root of the\n"
 "  filesystem.\n"
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 "\n"
 "The following options are only used for VM development and may\n"
 "be changed in any future version:\n");
diff --git a/runtime/bin/namespace_android.cc b/runtime/bin/namespace_android.cc
index f5a2a9fe9a4..26fe976f2f5 100644
--- a/runtime/bin/namespace_android.cc
+++ b/runtime/bin/namespace_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/namespace.h"
 
@@ -156,4 +156,4 @@ NamespaceScope::~NamespaceScope() {}
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/namespace_fuchsia.cc b/runtime/bin/namespace_fuchsia.cc
index c8cfbcb32d3..87a50aaab0a 100644
--- a/runtime/bin/namespace_fuchsia.cc
+++ b/runtime/bin/namespace_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/namespace.h"
 #include "bin/namespace_fuchsia.h"
@@ -167,4 +167,4 @@ NamespaceScope::~NamespaceScope() {}
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/namespace_fuchsia.h b/runtime/bin/namespace_fuchsia.h
index ef1fff2f3ab..49d2a7c8e99 100644
--- a/runtime/bin/namespace_fuchsia.h
+++ b/runtime/bin/namespace_fuchsia.h
@@ -6,7 +6,7 @@
 #define RUNTIME_BIN_NAMESPACE_FUCHSIA_H_
 
 #include "platform/globals.h"
-#if !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_FUCHSIA)
 #error "This header file should only be included when targeting Fuchsia."
 #endif
 
diff --git a/runtime/bin/namespace_linux.cc b/runtime/bin/namespace_linux.cc
index 416ea3dee0e..c3d6d7f8ffa 100644
--- a/runtime/bin/namespace_linux.cc
+++ b/runtime/bin/namespace_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/namespace.h"
 
@@ -156,4 +156,4 @@ NamespaceScope::~NamespaceScope() {}
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/namespace_macos.cc b/runtime/bin/namespace_macos.cc
index f6e55c1b72c..32b8eed0018 100644
--- a/runtime/bin/namespace_macos.cc
+++ b/runtime/bin/namespace_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/namespace.h"
 
@@ -64,4 +64,4 @@ NamespaceScope::~NamespaceScope() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/namespace_win.cc b/runtime/bin/namespace_win.cc
index 09a05f5db34..c654d41c7a7 100644
--- a/runtime/bin/namespace_win.cc
+++ b/runtime/bin/namespace_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/namespace.h"
 
@@ -74,4 +74,4 @@ NamespaceScope::~NamespaceScope() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/platform.h b/runtime/bin/platform.h
index 0a7db281103..bf2d6b1bde3 100644
--- a/runtime/bin/platform.h
+++ b/runtime/bin/platform.h
@@ -9,9 +9,9 @@
 #include "platform/globals.h"
 #include "platform/utils.h"
 
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 #include "bin/platform_macos.h"
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
 
 namespace dart {
 namespace bin {
diff --git a/runtime/bin/platform_android.cc b/runtime/bin/platform_android.cc
index 65559657129..6e5a34a0905 100644
--- a/runtime/bin/platform_android.cc
+++ b/runtime/bin/platform_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/platform.h"
 
@@ -173,4 +173,4 @@ void Platform::SetCoreDumpResourceLimit(int value) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/platform_fuchsia.cc b/runtime/bin/platform_fuchsia.cc
index 3fa55be9c33..5c23480fcee 100644
--- a/runtime/bin/platform_fuchsia.cc
+++ b/runtime/bin/platform_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/platform.h"
 
@@ -164,4 +164,4 @@ void Platform::SetCoreDumpResourceLimit(int value) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/platform_linux.cc b/runtime/bin/platform_linux.cc
index e6571aff5c6..d9443bb1e2c 100644
--- a/runtime/bin/platform_linux.cc
+++ b/runtime/bin/platform_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/platform.h"
 
@@ -180,4 +180,4 @@ void Platform::SetCoreDumpResourceLimit(int value) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/platform_macos.cc b/runtime/bin/platform_macos.cc
index f7c4c8cc4b2..0479776b531 100644
--- a/runtime/bin/platform_macos.cc
+++ b/runtime/bin/platform_macos.cc
@@ -3,16 +3,16 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/platform.h"
 #include "bin/platform_macos.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 
-#if !HOST_OS_IOS
+#if !DART_HOST_OS_IOS
 #include <crt_externs.h>  // NOLINT
-#endif                    // !HOST_OS_IOS
+#endif                    // !DART_HOST_OS_IOS
 #include <errno.h>        // NOLINT
 #include <mach-o/dyld.h>
 #include <signal.h>        // NOLINT
@@ -107,7 +107,7 @@ int Platform::NumberOfProcessors() {
 }
 
 const char* Platform::OperatingSystem() {
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
   return "ios";
 #else
   return "macos";
@@ -262,7 +262,7 @@ bool Platform::LocalHostname(char* buffer, intptr_t buffer_length) {
 }
 
 char** Platform::Environment(intptr_t* count) {
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
   // TODO(zra,chinmaygarde): On iOS, environment variables are seldom used. Wire
   // this up if someone needs it. In the meantime, we return an empty array.
   char** result;
@@ -343,4 +343,4 @@ void Platform::SetCoreDumpResourceLimit(int value) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/platform_macos_test.cc b/runtime/bin/platform_macos_test.cc
index 052d5411f4e..3c37901d596 100644
--- a/runtime/bin/platform_macos_test.cc
+++ b/runtime/bin/platform_macos_test.cc
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 #include "bin/platform.h"
 #include "vm/unit_test.h"
 
@@ -50,4 +50,4 @@ TEST_CASE(Platform_ExtractsOSVersionFromString) {
 }
 
 }  // namespace dart
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/platform_win.cc b/runtime/bin/platform_win.cc
index 552e3c2acfb..59e1b74ccd4 100644
--- a/runtime/bin/platform_win.cc
+++ b/runtime/bin/platform_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/platform.h"
 
@@ -319,4 +319,4 @@ void Platform::SetCoreDumpResourceLimit(int value) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/process.h b/runtime/bin/process.h
index cf141b20f82..5a6adfdc6fc 100644
--- a/runtime/bin/process.h
+++ b/runtime/bin/process.h
@@ -13,7 +13,7 @@
 #include "bin/namespace.h"
 #include "bin/thread.h"
 #include "platform/globals.h"
-#if !defined(HOST_OS_WINDOWS)
+#if !defined(DART_HOST_OS_WINDOWS)
 #include "platform/signal_blocker.h"
 #endif
 #include "platform/utils.h"
@@ -348,8 +348,8 @@ class BufferListBase {
   DISALLOW_COPY_AND_ASSIGN(BufferListBase);
 };
 
-#if defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA) ||                    \
-    defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA) ||          \
+    defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS)
 class BufferList : public BufferListBase {
  public:
   BufferList() {}
@@ -366,13 +366,13 @@ class BufferList : public BufferListBase {
       ASSERT(free_size() > 0);
       ASSERT(free_size() <= kBufferSize);
       intptr_t block_size = dart::Utils::Minimum(free_size(), available);
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
       intptr_t bytes = NO_RETRY_EXPECTED(
           read(fd, reinterpret_cast<void*>(FreeSpaceAddress()), block_size));
 #else
       intptr_t bytes = TEMP_FAILURE_RETRY(
           read(fd, reinterpret_cast<void*>(FreeSpaceAddress()), block_size));
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
       if (bytes < 0) {
         return false;
       }
@@ -386,7 +386,7 @@ class BufferList : public BufferListBase {
  private:
   DISALLOW_COPY_AND_ASSIGN(BufferList);
 };
-#endif  // defined(HOST_OS_ANDROID) ...
+#endif  // defined(DART_HOST_OS_ANDROID) ...
 
 }  // namespace bin
 }  // namespace dart
diff --git a/runtime/bin/process_android.cc b/runtime/bin/process_android.cc
index 700de02151d..874d99a88c8 100644
--- a/runtime/bin/process_android.cc
+++ b/runtime/bin/process_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/process.h"
 
@@ -1159,4 +1159,4 @@ void Process::Cleanup() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/process_fuchsia.cc b/runtime/bin/process_fuchsia.cc
index f5495d8988b..f87c28c19b3 100644
--- a/runtime/bin/process_fuchsia.cc
+++ b/runtime/bin/process_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/process.h"
 
@@ -867,4 +867,4 @@ void Process::Cleanup() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/process_linux.cc b/runtime/bin/process_linux.cc
index d1897fa530c..c20649e313f 100644
--- a/runtime/bin/process_linux.cc
+++ b/runtime/bin/process_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/process.h"
 
@@ -1155,4 +1155,4 @@ void Process::Cleanup() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/process_macos.cc b/runtime/bin/process_macos.cc
index 78a84ba5f5c..f20c589435b 100644
--- a/runtime/bin/process_macos.cc
+++ b/runtime/bin/process_macos.cc
@@ -3,11 +3,11 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/process.h"
 
-#if !HOST_OS_IOS
+#if !DART_HOST_OS_IOS
 #include <crt_externs.h>  // NOLINT
 #endif
 #include <errno.h>      // NOLINT
@@ -468,7 +468,7 @@ class ProcessStarter {
       ReportChildError();
     }
 
-#if !HOST_OS_IOS
+#if !DART_HOST_OS_IOS
     if (program_environment_ != NULL) {
       // On MacOS you have to do a bit of magic to get to the
       // environment strings.
@@ -521,7 +521,7 @@ class ProcessStarter {
               (TEMP_FAILURE_RETRY(chdir(working_directory_)) == -1)) {
             ReportChildError();
           }
-#if !HOST_OS_IOS
+#if !DART_HOST_OS_IOS
           if (program_environment_ != NULL) {
             // On MacOS you have to do a bit of magic to get to the
             // environment strings.
@@ -1191,4 +1191,4 @@ void Process::Cleanup() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/process_win.cc b/runtime/bin/process_win.cc
index 3567d214ba8..1e3a02cade0 100644
--- a/runtime/bin/process_win.cc
+++ b/runtime/bin/process_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/process.h"
 
@@ -935,7 +935,7 @@ int64_t Process::CurrentRSS() {
 // https://docs.microsoft.com/en-us/windows/win32/api/psapi/nf-psapi-getprocessmemoryinfo
 // claims that GetProcessMemoryInfo is UWP compatible, it is actually not
 // hence this function cannot work when compiled in UWP mode.
-#ifdef TARGET_OS_WINDOWS_UWP
+#ifdef DART_TARGET_OS_WINDOWS_UWP
   return -1;
 #else
   PROCESS_MEMORY_COUNTERS pmc;
@@ -947,7 +947,7 @@ int64_t Process::CurrentRSS() {
 }
 
 int64_t Process::MaxRSS() {
-#ifdef TARGET_OS_WINDOWS_UWP
+#ifdef DART_TARGET_OS_WINDOWS_UWP
   return -1;
 #else
   PROCESS_MEMORY_COUNTERS pmc;
@@ -1140,4 +1140,4 @@ void Process::Cleanup() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/root_certificates_unsupported.cc b/runtime/bin/root_certificates_unsupported.cc
index e644665ee4d..400877c9787 100644
--- a/runtime/bin/root_certificates_unsupported.cc
+++ b/runtime/bin/root_certificates_unsupported.cc
@@ -5,7 +5,7 @@
 #if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID) ||                      \
+#if defined(DART_HOST_OS_MACOS) || defined(DART_HOST_OS_ANDROID) ||            \
     defined(DART_IO_ROOT_CERTS_DISABLED)
 
 namespace dart {
@@ -17,6 +17,6 @@ unsigned int root_certificates_pem_length = 0;
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID) || ...
+#endif  // defined(DART_HOST_OS_MACOS) || defined(DART_HOST_OS_ANDROID) || ...
 
 #endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
diff --git a/runtime/bin/secure_socket_filter.cc b/runtime/bin/secure_socket_filter.cc
index f515b924b99..efaa4175fb1 100644
--- a/runtime/bin/secure_socket_filter.cc
+++ b/runtime/bin/secure_socket_filter.cc
@@ -161,7 +161,7 @@ void FUNCTION_NAME(SecureSocket_NewX509CertificateWrapper)(
     Dart_NativeArguments args) {
 // This is to be used only in conjunction with certificate trust evaluator
 // running asynchronously, which is only used on mac/ios at the moment.
-#if !defined(HOST_OS_MACOS)
+#if !defined(DART_HOST_OS_MACOS)
   FATAL("This is to be used only on mac/ios platforms");
 #endif
   intptr_t x509_pointer = DartUtils::GetNativeIntptrArgument(args, 0);
diff --git a/runtime/bin/security_context_android.cc b/runtime/bin/security_context_android.cc
index e0e9378305e..9f39a18aed2 100644
--- a/runtime/bin/security_context_android.cc
+++ b/runtime/bin/security_context_android.cc
@@ -5,7 +5,7 @@
 #if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/security_context.h"
 
@@ -64,6 +64,6 @@ TrustEvaluateHandlerFunc SSLCertContext::GetTrustEvaluateHandler() const {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
 
 #endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
diff --git a/runtime/bin/security_context_fuchsia.cc b/runtime/bin/security_context_fuchsia.cc
index e8f2f7acdbb..35eba7989b8 100644
--- a/runtime/bin/security_context_fuchsia.cc
+++ b/runtime/bin/security_context_fuchsia.cc
@@ -5,7 +5,7 @@
 #if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/security_context.h"
 
@@ -57,6 +57,6 @@ TrustEvaluateHandlerFunc SSLCertContext::GetTrustEvaluateHandler() const {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
 
 #endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
diff --git a/runtime/bin/security_context_linux.cc b/runtime/bin/security_context_linux.cc
index b251a0a3861..b940c758797 100644
--- a/runtime/bin/security_context_linux.cc
+++ b/runtime/bin/security_context_linux.cc
@@ -5,7 +5,7 @@
 #if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/security_context.h"
 
@@ -83,6 +83,6 @@ TrustEvaluateHandlerFunc SSLCertContext::GetTrustEvaluateHandler() const {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
 
 #endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
diff --git a/runtime/bin/security_context_macos.cc b/runtime/bin/security_context_macos.cc
index 1cba22d2ecb..410a33b11b3 100644
--- a/runtime/bin/security_context_macos.cc
+++ b/runtime/bin/security_context_macos.cc
@@ -5,7 +5,7 @@
 #if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/security_context.h"
 
@@ -347,6 +347,6 @@ void SSLCertContext::TrustBuiltinRoots() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
 
 #endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
diff --git a/runtime/bin/security_context_win.cc b/runtime/bin/security_context_win.cc
index 6b19a89e15e..f61ae55433c 100644
--- a/runtime/bin/security_context_win.cc
+++ b/runtime/bin/security_context_win.cc
@@ -5,7 +5,7 @@
 #if !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/security_context.h"
 
@@ -20,7 +20,7 @@
 #include "bin/secure_socket_utils.h"
 #include "platform/syslog.h"
 
-#ifndef TARGET_OS_WINDOWS_UWP
+#ifndef DART_TARGET_OS_WINDOWS_UWP
 #pragma comment(lib, "crypt32.lib")
 #endif
 
@@ -42,7 +42,7 @@ static void PrintSSLErr(const char* str) {
   Syslog::PrintErr("%s %s\n", str, error_string);
 }
 
-#ifndef TARGET_OS_WINDOWS_UWP
+#ifndef DART_TARGET_OS_WINDOWS_UWP
 static bool AddCertificatesFromNamedSystemStore(const wchar_t* name,
                                                 DWORD store_type,
                                                 X509_STORE* store) {
@@ -158,13 +158,13 @@ static bool AddCertificatesFromSystemStore(DWORD store_type,
   }
   return true;
 }
-#endif  // ifdef TARGET_OS_WINDOWS_UWP
+#endif  // ifdef DART_TARGET_OS_WINDOWS_UWP
 
 // Add certificates from Windows trusted root store.
 static bool AddCertificatesFromRootStore(X509_STORE* store) {
 // The UWP platform doesn't support CertEnumCertificatesInStore hence
 // this function cannot work when compiled in UWP mode.
-#ifdef TARGET_OS_WINDOWS_UWP
+#ifdef DART_TARGET_OS_WINDOWS_UWP
   return false;
 #else
   if (!AddCertificatesFromSystemStore(CERT_SYSTEM_STORE_CURRENT_USER, store)) {
@@ -176,7 +176,7 @@ static bool AddCertificatesFromRootStore(X509_STORE* store) {
   }
 
   return true;
-#endif  // ifdef TARGET_OS_WINDOWS_UWP
+#endif  // ifdef DART_TARGET_OS_WINDOWS_UWP
 }
 
 void SSLCertContext::TrustBuiltinRoots() {
@@ -226,6 +226,6 @@ TrustEvaluateHandlerFunc SSLCertContext::GetTrustEvaluateHandler() const {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
 
 #endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
diff --git a/runtime/bin/snapshot_utils.cc b/runtime/bin/snapshot_utils.cc
index 5168ac57f8c..7361612b322 100644
--- a/runtime/bin/snapshot_utils.cc
+++ b/runtime/bin/snapshot_utils.cc
@@ -201,7 +201,7 @@ static AppSnapshot* TryReadAppSnapshotElf(
                 *isolate_data_buffer = nullptr,
                 *isolate_instructions_buffer = nullptr;
   Dart_LoadedElf* handle = nullptr;
-#if !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_FUCHSIA)
   if (force_load_elf_from_memory) {
 #endif
     File* const file =
@@ -218,7 +218,7 @@ static AppSnapshot* TryReadAppSnapshotElf(
                             &isolate_data_buffer, &isolate_instructions_buffer);
     delete memory;
     file->Release();
-#if !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_FUCHSIA)
   } else {
     handle = Dart_LoadELF(script_name, file_offset, &error, &vm_data_buffer,
                           &vm_instructions_buffer, &isolate_data_buffer,
@@ -349,7 +349,7 @@ AppSnapshot* Snapshot::TryReadAppSnapshot(const char* script_uri,
   // For testing AOT with the standalone embedder, we also support loading
   // from a dynamic library to simulate what happens on iOS.
 
-#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_MACOS)
+#if defined(DART_TARGET_OS_LINUX) || defined(DART_TARGET_OS_MACOS)
   // On Linux and OSX, resolve the script path before passing into dlopen()
   // since dlopen will not search the filesystem for paths like 'libtest.so'.
   std::unique_ptr<char, decltype(std::free)*> absolute_path{
diff --git a/runtime/bin/socket.cc b/runtime/bin/socket.cc
index 1e137dbdbcb..ec52dad47d1 100644
--- a/runtime/bin/socket.cc
+++ b/runtime/bin/socket.cc
@@ -208,12 +208,12 @@ Dart_Handle ListeningSocketRegistry::CreateUnixDomainBindListen(
     return result;
   }
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   // Abstract unix domain socket doesn't exist in file system.
   if (File::Exists(namespc, addr.un.sun_path) && path[0] != '@') {
 #else
   if (File::Exists(namespc, addr.un.sun_path)) {
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
     if (unix_domain_sockets_ != nullptr) {
       // If there is a socket listening on this file. Ensure
       // that it was created with `shared` mode and current `shared`
@@ -285,7 +285,7 @@ bool ListeningSocketRegistry::CloseOneSafe(OSSocket* os_socket,
   }
   // Unlink the socket file, if os_socket contains unix domain sockets.
   if (os_socket->address.addr.sa_family == AF_UNIX) {
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
     // If the socket is abstract, which has a path starting with a null byte,
     // unlink() is not necessary because the file doesn't exist.
     if (os_socket->address.un.sun_path[0] != '\0') {
@@ -293,7 +293,7 @@ bool ListeningSocketRegistry::CloseOneSafe(OSSocket* os_socket,
     }
 #else
     Utils::Unlink(os_socket->address.un.sun_path);
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
     // Remove os_socket from unix_domain_sockets_ list.
     OSSocket* prev = nullptr;
     OSSocket* current = unix_domain_sockets_;
@@ -409,7 +409,7 @@ void FUNCTION_NAME(Socket_CreateBindConnect)(Dart_NativeArguments args) {
 
 void FUNCTION_NAME(Socket_CreateUnixDomainBindConnect)(
     Dart_NativeArguments args) {
-#if defined(HOST_OS_WINDOWS) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_WINDOWS) || defined(DART_HOST_OS_FUCHSIA)
   OSError os_error(
       -1, "Unix domain sockets are not available on this operating system.",
       OSError::kUnknown);
@@ -450,11 +450,11 @@ void FUNCTION_NAME(Socket_CreateUnixDomainBindConnect)(
   } else {
     Dart_SetReturnValue(args, DartUtils::NewDartOSError());
   }
-#endif  // defined(HOST_OS_WINDOWS) || defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_WINDOWS) || defined(DART_HOST_OS_FUCHSIA)
 }
 
 void FUNCTION_NAME(Socket_CreateUnixDomainConnect)(Dart_NativeArguments args) {
-#if defined(HOST_OS_WINDOWS) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_WINDOWS) || defined(DART_HOST_OS_FUCHSIA)
   OSError os_error(
       -1, "Unix domain sockets are not available on this operating system.",
       OSError::kUnknown);
@@ -481,7 +481,7 @@ void FUNCTION_NAME(Socket_CreateUnixDomainConnect)(Dart_NativeArguments args) {
   } else {
     Dart_SetReturnValue(args, DartUtils::NewDartOSError());
   }
-#endif  // defined(HOST_OS_WINDOWS) || defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_WINDOWS) || defined(DART_HOST_OS_FUCHSIA)
 }
 
 void FUNCTION_NAME(Socket_CreateBindDatagram)(Dart_NativeArguments args) {
@@ -855,7 +855,7 @@ void FUNCTION_NAME(ServerSocket_CreateBindListen)(Dart_NativeArguments args) {
 
 void FUNCTION_NAME(ServerSocket_CreateUnixDomainBindListen)(
     Dart_NativeArguments args) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   OSError os_error(
       -1, "Unix domain sockets are not available on this operating system.",
       OSError::kUnknown);
@@ -876,7 +876,7 @@ void FUNCTION_NAME(ServerSocket_CreateUnixDomainBindListen)(
       ListeningSocketRegistry::Instance()->CreateUnixDomainBindListen(
           socket_object, namespc, path, backlog, shared);
   Dart_SetReturnValue(args, result);
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
 }
 
 void FUNCTION_NAME(ServerSocket_Accept)(Dart_NativeArguments args) {
diff --git a/runtime/bin/socket.h b/runtime/bin/socket.h
index d7fc972c0f7..b0efe349a4a 100644
--- a/runtime/bin/socket.h
+++ b/runtime/bin/socket.h
@@ -262,7 +262,7 @@ class ListeningSocketRegistry {
                                  const char* path) {
     while (current != NULL) {
       ASSERT(current->address.addr.sa_family == AF_UNIX);
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
       bool condition;
       if (path[0] == '\0') {
         condition = current->address.un.sun_path[0] == '\0' &&
@@ -280,7 +280,7 @@ class ListeningSocketRegistry {
                              namespc, path) == File::kIdentical) {
         return current;
       }
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
       current = current->next;
     }
     return NULL;
diff --git a/runtime/bin/socket_android.cc b/runtime/bin/socket_android.cc
index 196cb360612..deddbd2e22a 100644
--- a/runtime/bin/socket_android.cc
+++ b/runtime/bin/socket_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/socket.h"
 
@@ -280,4 +280,4 @@ intptr_t ServerSocket::Accept(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/socket_base.cc b/runtime/bin/socket_base.cc
index d97ced4cba8..482163e0fab 100644
--- a/runtime/bin/socket_base.cc
+++ b/runtime/bin/socket_base.cc
@@ -128,7 +128,7 @@ void SocketAddress::GetSockAddr(Dart_Handle obj, RawAddr* addr) {
 Dart_Handle SocketAddress::GetUnixDomainSockAddr(const char* path,
                                                  Namespace* namespc,
                                                  RawAddr* addr) {
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   NamespaceScope ns(namespc, path);
   path = ns.path();
   bool is_abstract = (path[0] == '@');
@@ -139,7 +139,7 @@ Dart_Handle SocketAddress::GetUnixDomainSockAddr(const char* path,
     // connection will be rejected.
     bzero(addr->un.sun_path, sizeof(addr->un.sun_path));
   }
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   if (sizeof(path) > sizeof(addr->un.sun_path)) {
     OSError os_error(-1,
                      "The length of path exceeds the limit. "
@@ -149,12 +149,12 @@ Dart_Handle SocketAddress::GetUnixDomainSockAddr(const char* path,
   }
   addr->un.sun_family = AF_UNIX;
   Utils::SNPrint(addr->un.sun_path, sizeof(addr->un.sun_path), "%s", path);
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   // In case of abstract namespace, transfer the leading '@' into a null byte.
   if (is_abstract) {
     addr->un.sun_path[0] = '\0';
   }
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   return Dart_Null();
 }
 
diff --git a/runtime/bin/socket_base.h b/runtime/bin/socket_base.h
index 07ee42efa60..0442e5bd416 100644
--- a/runtime/bin/socket_base.h
+++ b/runtime/bin/socket_base.h
@@ -7,15 +7,15 @@
 
 #include "platform/globals.h"
 // Declare the OS-specific types ahead of defining the generic class.
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 #include "bin/socket_base_android.h"
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
 #include "bin/socket_base_fuchsia.h"
-#elif defined(HOST_OS_LINUX)
+#elif defined(DART_HOST_OS_LINUX)
 #include "bin/socket_base_linux.h"
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include "bin/socket_base_macos.h"
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 #include "bin/socket_base_win.h"
 #else
 #error Unknown target os.
@@ -86,7 +86,8 @@ class SocketAddress {
   static intptr_t GetAddrScope(const RawAddr& addr);
 
  private:
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID)
   // Unix domain address is only on Linux, Mac OS and Android now.
   // unix(7) require sun_path to be 108 bytes on Linux and Android, 104 bytes on
   // Mac OS.
@@ -95,8 +96,8 @@ class SocketAddress {
   char as_string_[kMaxUnixPathLength];
 #else
   char as_string_[INET6_ADDRSTRLEN];
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                 \
-        // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||       \
+        // defined(DART_HOST_OS_ANDROID)
   RawAddr addr_;
 
   DISALLOW_COPY_AND_ASSIGN(SocketAddress);
diff --git a/runtime/bin/socket_base_android.cc b/runtime/bin/socket_base_android.cc
index 68163c6f61a..f916aee694d 100644
--- a/runtime/bin/socket_base_android.cc
+++ b/runtime/bin/socket_base_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/socket_base.h"
 
@@ -470,4 +470,4 @@ bool SocketBase::LeaveMulticast(intptr_t fd,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/socket_base_fuchsia.cc b/runtime/bin/socket_base_fuchsia.cc
index be1eb256a49..5f36731080d 100644
--- a/runtime/bin/socket_base_fuchsia.cc
+++ b/runtime/bin/socket_base_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/socket_base.h"
 
@@ -429,4 +429,4 @@ bool SocketBase::LeaveMulticast(intptr_t fd,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/socket_base_linux.cc b/runtime/bin/socket_base_linux.cc
index 89e579f50d4..01d9d22655d 100644
--- a/runtime/bin/socket_base_linux.cc
+++ b/runtime/bin/socket_base_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/socket_base.h"
 
@@ -472,4 +472,4 @@ bool SocketBase::LeaveMulticast(intptr_t fd,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/socket_base_macos.cc b/runtime/bin/socket_base_macos.cc
index 0b259eef8e6..cb26ed42d5b 100644
--- a/runtime/bin/socket_base_macos.cc
+++ b/runtime/bin/socket_base_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/socket_base.h"
 
@@ -484,4 +484,4 @@ bool SocketBase::LeaveMulticast(intptr_t fd,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/socket_base_win.cc b/runtime/bin/socket_base_win.cc
index d762ad9d33d..120d42f5ca0 100644
--- a/runtime/bin/socket_base_win.cc
+++ b/runtime/bin/socket_base_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/socket_base.h"
 
@@ -489,4 +489,4 @@ bool SocketBase::LeaveMulticast(intptr_t fd,
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/socket_fuchsia.cc b/runtime/bin/socket_fuchsia.cc
index fa8a95837f5..9408ced941d 100644
--- a/runtime/bin/socket_fuchsia.cc
+++ b/runtime/bin/socket_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/socket.h"
 
@@ -266,4 +266,4 @@ intptr_t ServerSocket::Accept(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/socket_linux.cc b/runtime/bin/socket_linux.cc
index 686852f2b85..166979c7d3d 100644
--- a/runtime/bin/socket_linux.cc
+++ b/runtime/bin/socket_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/socket.h"
 
@@ -277,4 +277,4 @@ intptr_t ServerSocket::Accept(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/socket_macos.cc b/runtime/bin/socket_macos.cc
index f9e00c2c0ff..0e2767b06f3 100644
--- a/runtime/bin/socket_macos.cc
+++ b/runtime/bin/socket_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/socket.h"
 
@@ -294,4 +294,4 @@ intptr_t ServerSocket::Accept(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/socket_win.cc b/runtime/bin/socket_win.cc
index 4e393dcb99a..ac93b317ae3 100644
--- a/runtime/bin/socket_win.cc
+++ b/runtime/bin/socket_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/builtin.h"
 #include "bin/eventhandler.h"
@@ -315,4 +315,4 @@ bool ServerSocket::StartAccept(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/stdio_android.cc b/runtime/bin/stdio_android.cc
index f019f25fbff..1afb34fecd7 100644
--- a/runtime/bin/stdio_android.cc
+++ b/runtime/bin/stdio_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/stdio.h"
 
@@ -111,4 +111,4 @@ bool Stdout::AnsiSupported(intptr_t fd, bool* supported) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/stdio_fuchsia.cc b/runtime/bin/stdio_fuchsia.cc
index a626fee31e4..2f91a9c5440 100644
--- a/runtime/bin/stdio_fuchsia.cc
+++ b/runtime/bin/stdio_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/stdio.h"
 
@@ -62,4 +62,4 @@ bool Stdout::AnsiSupported(intptr_t fd, bool* supported) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/stdio_linux.cc b/runtime/bin/stdio_linux.cc
index 50e25f3eae0..17db9bd8e95 100644
--- a/runtime/bin/stdio_linux.cc
+++ b/runtime/bin/stdio_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/stdio.h"
 
@@ -111,4 +111,4 @@ bool Stdout::AnsiSupported(intptr_t fd, bool* supported) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/stdio_macos.cc b/runtime/bin/stdio_macos.cc
index 3b1aa5e9e46..969b75dc049 100644
--- a/runtime/bin/stdio_macos.cc
+++ b/runtime/bin/stdio_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/stdio.h"
 
@@ -111,4 +111,4 @@ bool Stdout::AnsiSupported(intptr_t fd, bool* supported) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/stdio_win.cc b/runtime/bin/stdio_win.cc
index cbfc2d89519..dc65cbaa3b8 100644
--- a/runtime/bin/stdio_win.cc
+++ b/runtime/bin/stdio_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/stdio.h"
 
@@ -136,4 +136,4 @@ bool Stdout::AnsiSupported(intptr_t fd, bool* supported) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/sync_socket_android.cc b/runtime/bin/sync_socket_android.cc
index 80094f728e6..b38f8090eb9 100644
--- a/runtime/bin/sync_socket_android.cc
+++ b/runtime/bin/sync_socket_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/sync_socket.h"
 
@@ -89,4 +89,4 @@ void SynchronousSocket::Close(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/sync_socket_fuchsia.cc b/runtime/bin/sync_socket_fuchsia.cc
index 23461f4ff4d..2775e5bce72 100644
--- a/runtime/bin/sync_socket_fuchsia.cc
+++ b/runtime/bin/sync_socket_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/sync_socket.h"
 
@@ -89,4 +89,4 @@ void SynchronousSocket::Close(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/sync_socket_linux.cc b/runtime/bin/sync_socket_linux.cc
index 963787bf7b9..5c72f32d656 100644
--- a/runtime/bin/sync_socket_linux.cc
+++ b/runtime/bin/sync_socket_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/sync_socket.h"
 
@@ -89,4 +89,4 @@ void SynchronousSocket::Close(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/sync_socket_macos.cc b/runtime/bin/sync_socket_macos.cc
index e266341be87..83535b85d2e 100644
--- a/runtime/bin/sync_socket_macos.cc
+++ b/runtime/bin/sync_socket_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/sync_socket.h"
 
@@ -92,4 +92,4 @@ void SynchronousSocket::Close(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/sync_socket_win.cc b/runtime/bin/sync_socket_win.cc
index d4e72fee4b7..d690e293315 100644
--- a/runtime/bin/sync_socket_win.cc
+++ b/runtime/bin/sync_socket_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/socket_base.h"
 #include "bin/sync_socket.h"
@@ -96,4 +96,4 @@ void SynchronousSocket::Close(intptr_t fd) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/test_extension_dllmain_win.cc b/runtime/bin/test_extension_dllmain_win.cc
index 2cee3110197..161913ba120 100644
--- a/runtime/bin/test_extension_dllmain_win.cc
+++ b/runtime/bin/test_extension_dllmain_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>  // NOLINT
@@ -12,4 +12,4 @@ BOOL APIENTRY DllMain(HMODULE module, DWORD reason, LPVOID reserved) {
   return true;
 }
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/thread.h b/runtime/bin/thread.h
index 09c9743e601..d6716c9c02a 100644
--- a/runtime/bin/thread.h
+++ b/runtime/bin/thread.h
@@ -16,15 +16,15 @@ class Monitor;
 }  // namespace dart
 
 // Declare the OS-specific types ahead of defining the generic classes.
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 #include "bin/thread_android.h"
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
 #include "bin/thread_fuchsia.h"
-#elif defined(HOST_OS_LINUX)
+#elif defined(DART_HOST_OS_LINUX)
 #include "bin/thread_linux.h"
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include "bin/thread_macos.h"
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 #include "bin/thread_win.h"
 #else
 #error Unknown target os.
diff --git a/runtime/bin/thread_android.cc b/runtime/bin/thread_android.cc
index 28b47adf648..d386ceb9d3d 100644
--- a/runtime/bin/thread_android.cc
+++ b/runtime/bin/thread_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "bin/thread.h"
 #include "bin/thread_android.h"
@@ -298,4 +298,4 @@ void Monitor::NotifyAll() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/thread_fuchsia.cc b/runtime/bin/thread_fuchsia.cc
index d71a1dfa435..66b847d1551 100644
--- a/runtime/bin/thread_fuchsia.cc
+++ b/runtime/bin/thread_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "bin/thread.h"
 #include "bin/thread_fuchsia.h"
@@ -305,4 +305,4 @@ void Monitor::NotifyAll() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/thread_linux.cc b/runtime/bin/thread_linux.cc
index 2b3a7e6f32a..b671d0c890a 100644
--- a/runtime/bin/thread_linux.cc
+++ b/runtime/bin/thread_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "bin/thread.h"
 #include "bin/thread_linux.h"
@@ -301,4 +301,4 @@ void Monitor::NotifyAll() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/thread_macos.cc b/runtime/bin/thread_macos.cc
index af636f0094a..a38c44129a8 100644
--- a/runtime/bin/thread_macos.cc
+++ b/runtime/bin/thread_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "bin/thread.h"
 #include "bin/thread_macos.h"
@@ -294,4 +294,4 @@ void Monitor::NotifyAll() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/thread_win.cc b/runtime/bin/thread_win.cc
index ef6b6320b03..53809f364e7 100644
--- a/runtime/bin/thread_win.cc
+++ b/runtime/bin/thread_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "bin/thread.h"
 #include "bin/thread_win.h"
@@ -192,4 +192,4 @@ void Monitor::NotifyAll() {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/utils_android.cc b/runtime/bin/utils_android.cc
index ed6b5de8af3..53a4cec4d0a 100644
--- a/runtime/bin/utils_android.cc
+++ b/runtime/bin/utils_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include <errno.h>     // NOLINT
 #include <netdb.h>     // NOLINT
@@ -115,4 +115,4 @@ void TimerUtils::Sleep(int64_t millis) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/bin/utils_fuchsia.cc b/runtime/bin/utils_fuchsia.cc
index c7bbe081c9f..f034e87bc07 100644
--- a/runtime/bin/utils_fuchsia.cc
+++ b/runtime/bin/utils_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include <errno.h>
 #include <zircon/syscalls.h>
@@ -89,4 +89,4 @@ void TimerUtils::Sleep(int64_t millis) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/bin/utils_linux.cc b/runtime/bin/utils_linux.cc
index b87778aa0ae..9c9ad3a5077 100644
--- a/runtime/bin/utils_linux.cc
+++ b/runtime/bin/utils_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include <errno.h>     // NOLINT
 #include <netdb.h>     // NOLINT
@@ -114,4 +114,4 @@ void TimerUtils::Sleep(int64_t millis) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/bin/utils_macos.cc b/runtime/bin/utils_macos.cc
index 52066bc2f79..219d643f087 100644
--- a/runtime/bin/utils_macos.cc
+++ b/runtime/bin/utils_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include <errno.h>           // NOLINT
 #include <mach/clock.h>      // NOLINT
@@ -120,4 +120,4 @@ void TimerUtils::Sleep(int64_t millis) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/bin/utils_win.cc b/runtime/bin/utils_win.cc
index f73bd20eb6d..fcbbcbbe3c6 100644
--- a/runtime/bin/utils_win.cc
+++ b/runtime/bin/utils_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include <errno.h>  // NOLINT
 #include <time.h>   // NOLINT
@@ -224,4 +224,4 @@ void TimerUtils::Sleep(int64_t millis) {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/bin/vmservice_impl.cc b/runtime/bin/vmservice_impl.cc
index 47b799233d8..4f82645a60f 100644
--- a/runtime/bin/vmservice_impl.cc
+++ b/runtime/bin/vmservice_impl.cc
@@ -197,7 +197,7 @@ bool VmService::Setup(const char* server_ip,
   SHUTDOWN_ON_ERROR(result);
 
 // Are we running on Windows?
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   Dart_Handle is_windows = Dart_True();
 #else
   Dart_Handle is_windows = Dart_False();
@@ -207,7 +207,7 @@ bool VmService::Setup(const char* server_ip,
   SHUTDOWN_ON_ERROR(result);
 
 // Are we running on Fuchsia?
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
   Dart_Handle is_fuchsia = Dart_True();
 #else
   Dart_Handle is_fuchsia = Dart_False();
diff --git a/runtime/lib/double.cc b/runtime/lib/double.cc
index 09136b739eb..bc7c33bc19d 100644
--- a/runtime/lib/double.cc
+++ b/runtime/lib/double.cc
@@ -4,7 +4,7 @@
 
 #include "vm/bootstrap_natives.h"
 
-#include <math.h>
+#include <math.h>  // NOLINT
 
 #include "vm/dart_entry.h"
 #include "vm/double_conversion.h"
@@ -180,7 +180,7 @@ DEFINE_NATIVE_ENTRY(Double_truncate, 0, 1) {
   return Double::New(trunc(arg.value()));
 }
 
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 // MAC OSX math library produces old style cast warning.
 #pragma GCC diagnostic ignored "-Wold-style-cast"
 #endif
diff --git a/runtime/lib/ffi_dynamic_library.cc b/runtime/lib/ffi_dynamic_library.cc
index eb8e74b5c18..b2f8c3749ff 100644
--- a/runtime/lib/ffi_dynamic_library.cc
+++ b/runtime/lib/ffi_dynamic_library.cc
@@ -8,8 +8,8 @@
 #include "vm/globals.h"
 #include "vm/native_entry.h"
 
-#if !defined(HOST_OS_LINUX) && !defined(HOST_OS_MACOS) &&                      \
-    !defined(HOST_OS_ANDROID) && !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_LINUX) && !defined(DART_HOST_OS_MACOS) &&            \
+    !defined(DART_HOST_OS_ANDROID) && !defined(DART_HOST_OS_FUCHSIA)
 // TODO(dacoharkes): Implement dynamic libraries for other targets & merge the
 // implementation with:
 // - runtime/bin/extensions.h
@@ -23,8 +23,8 @@
 namespace dart {
 
 static void* LoadExtensionLibrary(const char* library_file) {
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                        \
-    defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA)
   void* handle = dlopen(library_file, RTLD_LAZY);
   if (handle == nullptr) {
     char* error = dlerror();
@@ -34,7 +34,7 @@ static void* LoadExtensionLibrary(const char* library_file) {
   }
 
   return handle;
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
   SetLastError(0);  // Clear any errors.
 
   void* ext;
@@ -78,8 +78,8 @@ DEFINE_NATIVE_ENTRY(Ffi_dl_open, 0, 1) {
 }
 
 DEFINE_NATIVE_ENTRY(Ffi_dl_processLibrary, 0, 0) {
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                        \
-    defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA)
   return DynamicLibrary::New(RTLD_DEFAULT);
 #else
   const Array& args = Array::Handle(Array::New(1));
@@ -95,8 +95,8 @@ DEFINE_NATIVE_ENTRY(Ffi_dl_executableLibrary, 0, 0) {
 }
 
 static void* ResolveSymbol(void* handle, const char* symbol) {
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                        \
-    defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA)
   dlerror();  // Clear any errors.
   void* pointer = dlsym(handle, symbol);
   char* error = dlerror();
@@ -106,7 +106,7 @@ static void* ResolveSymbol(void* handle, const char* symbol) {
     Exceptions::ThrowArgumentError(msg);
   }
   return pointer;
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
   SetLastError(0);
   void* pointer = reinterpret_cast<void*>(
       GetProcAddress(reinterpret_cast<HMODULE>(handle), symbol));
@@ -148,14 +148,14 @@ DEFINE_NATIVE_ENTRY(Ffi_dl_getHandle, 0, 1) {
 }
 
 static bool SymbolExists(void* handle, const char* symbol) {
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                        \
-    defined(HOST_OS_ANDROID) || defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_FUCHSIA)
   dlerror();  // Clear previous error, if any.
   dlsym(handle, symbol);
   // Checking whether dlsym returns a nullptr is not enough, as the value of
   // the symbol could actually be NULL. Check the error condition instead.
   return dlerror() == nullptr;
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
   return GetProcAddress(reinterpret_cast<HMODULE>(handle), symbol) != nullptr;
 #else
   const Array& args = Array::Handle(Array::New(1));
diff --git a/runtime/lib/uri.cc b/runtime/lib/uri.cc
index af4c65df9ae..06df6d73dfd 100644
--- a/runtime/lib/uri.cc
+++ b/runtime/lib/uri.cc
@@ -9,7 +9,7 @@
 namespace dart {
 
 DEFINE_NATIVE_ENTRY(Uri_isWindowsPlatform, 0, 0) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   return Bool::True().ptr();
 #else
   return Bool::False().ptr();
diff --git a/runtime/platform/assert.cc b/runtime/platform/assert.cc
index 85e4ea2dcb9..5c7bf0b3c04 100644
--- a/runtime/platform/assert.cc
+++ b/runtime/platform/assert.cc
@@ -8,9 +8,9 @@
 #include "platform/globals.h"
 #include "platform/syslog.h"
 
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 extern "C" __attribute__((weak)) void android_set_abort_message(const char*);
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
 
 namespace dart {
 
@@ -36,11 +36,11 @@ void DynamicAssertionHelper::Print(const char* format,
 
   // Print the buffer on stderr and/or syslog.
   Syslog::PrintErr("%s\n", buffer);
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
   if (will_abort && (&android_set_abort_message != nullptr)) {
     android_set_abort_message(buffer);
   }
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
 }
 
 void Assert::Fail(const char* format, ...) {
diff --git a/runtime/platform/floating_point_win.cc b/runtime/platform/floating_point_win.cc
index 7fffe7aa2cc..6e853d6dfcd 100644
--- a/runtime/platform/floating_point_win.cc
+++ b/runtime/platform/floating_point_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "platform/floating_point_win.h"
 
@@ -46,4 +46,4 @@ double atan2_ieee(double x, double y) {
   }
 }
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/platform/globals.h b/runtime/platform/globals.h
index cc8eec102be..42edc706c1b 100644
--- a/runtime/platform/globals.h
+++ b/runtime/platform/globals.h
@@ -106,33 +106,31 @@
 #if defined(__ANDROID__)
 
 // Check for Android first, to determine its difference from Linux.
-#define HOST_OS_ANDROID 1
+#define DART_HOST_OS_ANDROID 1
 
 #elif defined(__linux__) || defined(__FreeBSD__)
 
 // Generic Linux.
-#define HOST_OS_LINUX 1
+#define DART_HOST_OS_LINUX 1
 
 #elif defined(__APPLE__)
 
 // Define the flavor of Mac OS we are running on.
 #include <TargetConditionals.h>
-// TODO(iposva): Rename HOST_OS_MACOS to HOST_OS_MAC to inherit
-// the value defined in TargetConditionals.h
-#define HOST_OS_MACOS 1
+#define DART_HOST_OS_MACOS 1
 #if TARGET_OS_IPHONE
-#define HOST_OS_IOS 1
+#define DART_HOST_OS_IOS 1
 #endif
 
 #elif defined(_WIN32)
 
 // Windows, both 32- and 64-bit, regardless of the check for _WIN32.
-#define HOST_OS_WINDOWS 1
+#define DART_HOST_OS_WINDOWS 1
 
 #elif defined(__Fuchsia__)
-#define HOST_OS_FUCHSIA
+#define DART_HOST_OS_FUCHSIA
 
-#elif !defined(HOST_OS_FUCHSIA)
+#elif !defined(DART_HOST_OS_FUCHSIA)
 #error Automatic target os detection failed.
 #endif
 
@@ -374,23 +372,23 @@ typedef simd128_value_t fpu_register_t;
 #error Unknown architecture.
 #endif
 
-#if !defined(TARGET_OS_ANDROID) && !defined(TARGET_OS_FUCHSIA) &&              \
-    !defined(TARGET_OS_MACOS_IOS) && !defined(TARGET_OS_LINUX) &&              \
-    !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_WINDOWS)
+#if !defined(DART_TARGET_OS_ANDROID) && !defined(DART_TARGET_OS_FUCHSIA) &&    \
+    !defined(DART_TARGET_OS_MACOS_IOS) && !defined(DART_TARGET_OS_LINUX) &&    \
+    !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_WINDOWS)
 // No target OS specified; pick the one matching the host OS.
-#if defined(HOST_OS_ANDROID)
-#define TARGET_OS_ANDROID 1
-#elif defined(HOST_OS_FUCHSIA)
-#define TARGET_OS_FUCHSIA 1
-#elif defined(HOST_OS_IOS)
-#define TARGET_OS_MACOS 1
-#define TARGET_OS_MACOS_IOS 1
-#elif defined(HOST_OS_LINUX)
-#define TARGET_OS_LINUX 1
-#elif defined(HOST_OS_MACOS)
-#define TARGET_OS_MACOS 1
-#elif defined(HOST_OS_WINDOWS)
-#define TARGET_OS_WINDOWS 1
+#if defined(DART_HOST_OS_ANDROID)
+#define DART_TARGET_OS_ANDROID 1
+#elif defined(DART_HOST_OS_FUCHSIA)
+#define DART_TARGET_OS_FUCHSIA 1
+#elif defined(DART_HOST_OS_IOS)
+#define DART_TARGET_OS_MACOS 1
+#define DART_TARGET_OS_MACOS_IOS 1
+#elif defined(DART_HOST_OS_LINUX)
+#define DART_TARGET_OS_LINUX 1
+#elif defined(DART_HOST_OS_MACOS)
+#define DART_TARGET_OS_MACOS 1
+#elif defined(DART_HOST_OS_WINDOWS)
+#define DART_TARGET_OS_WINDOWS 1
 #else
 #error Automatic target OS detection failed.
 #endif
@@ -399,8 +397,8 @@ typedef simd128_value_t fpu_register_t;
 // Determine whether dual mapping of code pages is supported.
 // We test dual mapping on linux x64 and deploy it on fuchsia.
 #if !defined(DART_PRECOMPILED_RUNTIME) &&                                      \
-    (defined(TARGET_OS_LINUX) && defined(TARGET_ARCH_X64) ||                   \
-     defined(TARGET_OS_FUCHSIA))
+    (defined(DART_TARGET_OS_LINUX) && defined(TARGET_ARCH_X64) ||              \
+     defined(DART_TARGET_OS_FUCHSIA))
 #define DUAL_MAPPING_SUPPORTED 1
 #endif
 
@@ -670,19 +668,19 @@ inline D bit_copy(const S& source) {
 
 // On Windows the reentrent version of strtok is called
 // strtok_s. Unify on the posix name strtok_r.
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #define snprintf _sprintf_p
 #define strtok_r strtok_s
 #endif
 
-#if !defined(HOST_OS_WINDOWS)
+#if !defined(DART_HOST_OS_WINDOWS)
 #if defined(TEMP_FAILURE_RETRY)
 // TEMP_FAILURE_RETRY is defined in unistd.h on some platforms. We should
 // not use that version, but instead the one in signal_blocker.h, to ensure
 // we disable signal interrupts.
 #undef TEMP_FAILURE_RETRY
 #endif  // defined(TEMP_FAILURE_RETRY)
-#endif  // !defined(HOST_OS_WINDOWS)
+#endif  // !defined(DART_HOST_OS_WINDOWS)
 
 #if __GNUC__
 // Tell the compiler to do printf format string checking if the
diff --git a/runtime/platform/signal_blocker.h b/runtime/platform/signal_blocker.h
index c56c1da99c0..e47ac60f940 100644
--- a/runtime/platform/signal_blocker.h
+++ b/runtime/platform/signal_blocker.h
@@ -8,7 +8,7 @@
 #include "platform/assert.h"
 #include "platform/globals.h"
 
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #error Do not include this file on Windows.
 #endif
 
diff --git a/runtime/platform/syslog_android.cc b/runtime/platform/syslog_android.cc
index 9aa77c02083..46930e99e58 100644
--- a/runtime/platform/syslog_android.cc
+++ b/runtime/platform/syslog_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "platform/syslog.h"
 
@@ -35,4 +35,4 @@ void Syslog::VPrintErr(const char* format, va_list args) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/platform/syslog_fuchsia.cc b/runtime/platform/syslog_fuchsia.cc
index 85e4c80ff25..f9b0d65e7bc 100644
--- a/runtime/platform/syslog_fuchsia.cc
+++ b/runtime/platform/syslog_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "platform/syslog.h"
 
@@ -23,4 +23,4 @@ void Syslog::VPrintErr(const char* format, va_list args) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/platform/syslog_linux.cc b/runtime/platform/syslog_linux.cc
index 269bc9f28eb..ea73f2b6ff6 100644
--- a/runtime/platform/syslog_linux.cc
+++ b/runtime/platform/syslog_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "platform/syslog.h"
 
@@ -23,4 +23,4 @@ void Syslog::VPrintErr(const char* format, va_list args) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/platform/syslog_macos.cc b/runtime/platform/syslog_macos.cc
index f01bfbf19f7..bfb3a7e8ad7 100644
--- a/runtime/platform/syslog_macos.cc
+++ b/runtime/platform/syslog_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "platform/syslog.h"
 
@@ -23,4 +23,4 @@ void Syslog::VPrintErr(const char* format, va_list args) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/platform/syslog_win.cc b/runtime/platform/syslog_win.cc
index 07ab8156807..20833b7ce2f 100644
--- a/runtime/platform/syslog_win.cc
+++ b/runtime/platform/syslog_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "platform/syslog.h"
 
@@ -23,4 +23,4 @@ void Syslog::VPrintErr(const char* format, va_list args) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/platform/utils.cc b/runtime/platform/utils.cc
index 1ba74f7df40..d04c3a81413 100644
--- a/runtime/platform/utils.cc
+++ b/runtime/platform/utils.cc
@@ -57,7 +57,7 @@ int Utils::CountLeadingZeros64(uint64_t x) {
     return CountLeadingZeros32(x_hi);
   }
   return 32 + CountLeadingZeros32(static_cast<uint32_t>(x));
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
   unsigned long position;  // NOLINT
   return (_BitScanReverse64(&position, x) == 0)
              ? 64
@@ -68,7 +68,7 @@ int Utils::CountLeadingZeros64(uint64_t x) {
 }
 
 int Utils::CountLeadingZeros32(uint32_t x) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   unsigned long position;  // NOLINT
   return (_BitScanReverse(&position, x) == 0) ? 32
                                               : 31 - static_cast<int>(position);
@@ -84,7 +84,7 @@ int Utils::CountTrailingZeros64(uint64_t x) {
     return CountTrailingZeros32(x_lo);
   }
   return 32 + CountTrailingZeros32(static_cast<uint32_t>(x >> 32));
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
   unsigned long position;  // NOLINT
   return (_BitScanForward64(&position, x) == 0) ? 64
                                                 : static_cast<int>(position);
@@ -94,7 +94,7 @@ int Utils::CountTrailingZeros64(uint64_t x) {
 }
 
 int Utils::CountTrailingZeros32(uint32_t x) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   unsigned long position;  // NOLINT
   return (_BitScanForward(&position, x) == 0) ? 32 : static_cast<int>(position);
 #else
diff --git a/runtime/platform/utils.h b/runtime/platform/utils.h
index 41054c4362f..98f1a1c5237 100644
--- a/runtime/platform/utils.h
+++ b/runtime/platform/utils.h
@@ -481,15 +481,15 @@ class Utils {
 
 }  // namespace dart
 
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 #include "platform/utils_android.h"
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
 #include "platform/utils_fuchsia.h"
-#elif defined(HOST_OS_LINUX)
+#elif defined(DART_HOST_OS_LINUX)
 #include "platform/utils_linux.h"
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include "platform/utils_macos.h"
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 #include "platform/utils_win.h"
 #else
 #error Unknown target os.
diff --git a/runtime/platform/utils_android.cc b/runtime/platform/utils_android.cc
index 72618eb9ad1..6e14851c756 100644
--- a/runtime/platform/utils_android.cc
+++ b/runtime/platform/utils_android.cc
@@ -3,9 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "platform/utils.h"
+#include "platform/utils_android.h"
 
 namespace dart {
 
@@ -49,4 +50,4 @@ int Utils::Unlink(const char* path) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/platform/utils_fuchsia.cc b/runtime/platform/utils_fuchsia.cc
index a6d9f37292a..8f6c7acf219 100644
--- a/runtime/platform/utils_fuchsia.cc
+++ b/runtime/platform/utils_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include <memory>
 #include <utility>
@@ -78,4 +78,4 @@ std::unique_ptr<inspect::Node> TakeDartVmNode() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/platform/utils_linux.cc b/runtime/platform/utils_linux.cc
index c430bcac374..ec4aead20f6 100644
--- a/runtime/platform/utils_linux.cc
+++ b/runtime/platform/utils_linux.cc
@@ -3,9 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "platform/utils.h"
+#include "platform/utils_linux.h"
 
 namespace dart {
 
@@ -50,4 +51,4 @@ int Utils::Unlink(const char* path) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/platform/utils_macos.cc b/runtime/platform/utils_macos.cc
index a801746931e..9de2e431218 100644
--- a/runtime/platform/utils_macos.cc
+++ b/runtime/platform/utils_macos.cc
@@ -3,9 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "platform/utils.h"
+#include "platform/utils_macos.h"
 
 #include <errno.h>        // NOLINT
 #include <sys/utsname.h>  // NOLINT
@@ -150,4 +151,4 @@ int32_t MacOSXMinorVersion() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/platform/utils_win.cc b/runtime/platform/utils_win.cc
index 7ba2ec83215..25d2f1d573f 100644
--- a/runtime/platform/utils_win.cc
+++ b/runtime/platform/utils_win.cc
@@ -3,11 +3,13 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include <io.h>  // NOLINT
+
 #include "platform/allocation.h"
 #include "platform/utils.h"
+#include "platform/utils_win.h"
 
 namespace dart {
 
@@ -86,4 +88,4 @@ int Utils::Unlink(const char* path) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/tools/run_clang_tidy.dart b/runtime/tools/run_clang_tidy.dart
index 6e35ebac828..aa32b3bc505 100644
--- a/runtime/tools/run_clang_tidy.dart
+++ b/runtime/tools/run_clang_tidy.dart
@@ -20,7 +20,7 @@ List<String> compilerFlagsForFile(String filepath) {
     '-Ithird_party/zlib',
     '-DTARGET_ARCH_X64',
     '-DDEBUG',
-    '-DTARGET_OS_LINUX',
+    '-DDART_TARGET_OS_LINUX',
     '-DTESTING',
     '-std=c++17',
     '-x',
diff --git a/runtime/vm/compiler/assembler/assembler_arm.cc b/runtime/vm/compiler/assembler/assembler_arm.cc
index 63cba26df39..7cf827213bf 100644
--- a/runtime/vm/compiler/assembler/assembler_arm.cc
+++ b/runtime/vm/compiler/assembler/assembler_arm.cc
@@ -15,7 +15,7 @@
 
 // An extra check since we are assuming the existence of /proc/cpuinfo below.
 #if !defined(USING_SIMULATOR) && !defined(__linux__) && !defined(ANDROID) &&   \
-    !defined(HOST_OS_IOS) && !defined(HOST_OS_MACOS)
+    !defined(DART_HOST_OS_IOS) && !defined(DART_HOST_OS_MACOS)
 #error ARM cross-compile only supported on Linux, Android, iOS, and Mac
 #endif
 
diff --git a/runtime/vm/compiler/assembler/assembler_x64_test.cc b/runtime/vm/compiler/assembler/assembler_x64_test.cc
index 9704c220166..00eeead8119 100644
--- a/runtime/vm/compiler/assembler/assembler_x64_test.cc
+++ b/runtime/vm/compiler/assembler/assembler_x64_test.cc
@@ -32,7 +32,7 @@ namespace compiler {
   intptr_t exp_len = strlen(expected);                                         \
   EXPECT_GT(dis_len, exp_len);                                                 \
   EXPECT_STREQ(expected, disassembly + dis_len - exp_len);
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
 // Windows has different calling conventions on x64, which means the
 // disassembly looks different on some tests.  We skip testing the
 // disassembly output for those tests on Windows.
@@ -5435,7 +5435,7 @@ ASSEMBLER_TEST_RUN(DoubleToDoubleTrunc, test) {
 
 ASSEMBLER_TEST_GENERATE(DoubleAbs, assembler) {
   EnterTestFrame(assembler);
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   // First argument is code object, second argument is thread. MSVC passes
   // third argument in XMM2.
   __ DoubleAbs(XMM0, XMM2);
diff --git a/runtime/vm/compiler/backend/il_arm.cc b/runtime/vm/compiler/backend/il_arm.cc
index 0ac5dfd1eda..80aaa4759f3 100644
--- a/runtime/vm/compiler/backend/il_arm.cc
+++ b/runtime/vm/compiler/backend/il_arm.cc
@@ -1544,7 +1544,7 @@ void NativeReturnInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 
   __ PopNativeCalleeSavedRegisters();
 
-#if defined(TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
+#if defined(DART_TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
 #endif
 
@@ -1580,7 +1580,7 @@ void NativeEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // Save a space for the code object.
   __ PushImmediate(0);
 
-#if defined(TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
+#if defined(DART_TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
 #endif
 
diff --git a/runtime/vm/compiler/backend/il_arm64.cc b/runtime/vm/compiler/backend/il_arm64.cc
index 87cc6b7cd66..223b42423a6 100644
--- a/runtime/vm/compiler/backend/il_arm64.cc
+++ b/runtime/vm/compiler/backend/il_arm64.cc
@@ -1454,7 +1454,7 @@ void NativeEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // Now that we have THR, we can set CSP.
   __ SetupCSPFromThread(THR);
 
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
   __ str(R18,
          compiler::Address(
              THR, compiler::target::Thread::saved_shadow_call_stack_offset()));
diff --git a/runtime/vm/compiler/backend/il_ia32.cc b/runtime/vm/compiler/backend/il_ia32.cc
index f7ef9ae793c..ee1ab8c881b 100644
--- a/runtime/vm/compiler/backend/il_ia32.cc
+++ b/runtime/vm/compiler/backend/il_ia32.cc
@@ -331,7 +331,7 @@ void NativeReturnInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ popl(ESI);
   __ popl(EBX);
 
-#if defined(TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
+#if defined(DART_TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
 #endif
 
@@ -1131,7 +1131,7 @@ void NativeEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ xorl(EAX, EAX);
   __ pushl(EAX);
 
-#if defined(TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
+#if defined(DART_TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
 #endif
 
diff --git a/runtime/vm/compiler/backend/il_x64.cc b/runtime/vm/compiler/backend/il_x64.cc
index 7882a76846b..cb4c1beed1a 100644
--- a/runtime/vm/compiler/backend/il_x64.cc
+++ b/runtime/vm/compiler/backend/il_x64.cc
@@ -409,7 +409,7 @@ void NativeReturnInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // Restore C++ ABI callee-saved registers.
   __ PopRegisters(kCalleeSaveRegistersSet);
 
-#if defined(TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
+#if defined(DART_TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
 #endif
 
@@ -1310,7 +1310,7 @@ void NativeEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // NativeReturnInstr::EmitNativeCode.
   __ EnterFrame(0);
 
-#if defined(TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
+#if defined(DART_TARGET_OS_FUCHSIA) && defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
 #endif
 
diff --git a/runtime/vm/compiler/ffi/abi.cc b/runtime/vm/compiler/ffi/abi.cc
index 1d3bd8b919c..d71ad34868b 100644
--- a/runtime/vm/compiler/ffi/abi.cc
+++ b/runtime/vm/compiler/ffi/abi.cc
@@ -28,14 +28,14 @@ static_assert(offsetof(AbiAlignmentDouble, d) == 8,
 static_assert(offsetof(AbiAlignmentUint64, i) == 8,
               "FFI transformation alignment");
 #elif (defined(HOST_ARCH_IA32) && /* NOLINT(whitespace/parens) */              \
-       (defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) ||                    \
-        defined(HOST_OS_ANDROID))) ||                                          \
-    (defined(HOST_ARCH_ARM) && defined(HOST_OS_IOS))
+       (defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||          \
+        defined(DART_HOST_OS_ANDROID))) ||                                     \
+    (defined(HOST_ARCH_ARM) && defined(DART_HOST_OS_IOS))
 static_assert(offsetof(AbiAlignmentDouble, d) == 4,
               "FFI transformation alignment");
 static_assert(offsetof(AbiAlignmentUint64, i) == 4,
               "FFI transformation alignment");
-#elif defined(HOST_ARCH_IA32) && defined(HOST_OS_WINDOWS) ||                   \
+#elif defined(HOST_ARCH_IA32) && defined(DART_HOST_OS_WINDOWS) ||              \
     defined(HOST_ARCH_ARM)
 static_assert(offsetof(AbiAlignmentDouble, d) == 8,
               "FFI transformation alignment");
@@ -49,11 +49,11 @@ Abi TargetAbi() {
 #if defined(TARGET_ARCH_X64) || defined(TARGET_ARCH_ARM64)
   return Abi::kWordSize64;
 #elif (defined(TARGET_ARCH_IA32) && /* NOLINT(whitespace/parens) */            \
-       (defined(TARGET_OS_LINUX) || defined(TARGET_OS_MACOS) ||                \
-        defined(TARGET_OS_ANDROID))) ||                                        \
-    (defined(TARGET_ARCH_ARM) && defined(TARGET_OS_MACOS_IOS))
+       (defined(DART_TARGET_OS_LINUX) || defined(DART_TARGET_OS_MACOS) ||      \
+        defined(DART_TARGET_OS_ANDROID))) ||                                   \
+    (defined(TARGET_ARCH_ARM) && defined(DART_TARGET_OS_MACOS_IOS))
   return Abi::kWordSize32Align32;
-#elif defined(TARGET_ARCH_IA32) && defined(TARGET_OS_WINDOWS) ||               \
+#elif defined(TARGET_ARCH_IA32) && defined(DART_TARGET_OS_WINDOWS) ||          \
     defined(TARGET_ARCH_ARM)
   return Abi::kWordSize32Align64;
 #else
diff --git a/runtime/vm/compiler/ffi/native_calling_convention.cc b/runtime/vm/compiler/ffi/native_calling_convention.cc
index 8ed3646d272..0d810475f22 100644
--- a/runtime/vm/compiler/ffi/native_calling_convention.cc
+++ b/runtime/vm/compiler/ffi/native_calling_convention.cc
@@ -31,7 +31,7 @@ static bool SoftFpAbi() {
 }
 #else  // !defined(FFI_UNIT_TESTS)
 static bool SoftFpAbi() {
-#if defined(TARGET_ARCH_ARM) && defined(TARGET_OS_ANDROID)
+#if defined(TARGET_ARCH_ARM) && defined(DART_TARGET_OS_ANDROID)
   return true;
 #else
   return false;
@@ -135,7 +135,7 @@ class ArgumentAllocator : public ValueObject {
     return AllocateStack(payload_type);
   }
 
-#if defined(TARGET_ARCH_X64) && !defined(TARGET_OS_WINDOWS)
+#if defined(TARGET_ARCH_X64) && !defined(DART_TARGET_OS_WINDOWS)
   // If fits in two fpu and/or cpu registers, transfer in those. Otherwise,
   // transfer on stack.
   const NativeLocation& AllocateCompound(
@@ -177,9 +177,9 @@ class ArgumentAllocator : public ValueObject {
     }
     return AllocateStack(payload_type);
   }
-#endif  // defined(TARGET_ARCH_X64) && !defined(TARGET_OS_WINDOWS)
+#endif  // defined(TARGET_ARCH_X64) && !defined(DART_TARGET_OS_WINDOWS)
 
-#if defined(TARGET_ARCH_X64) && defined(TARGET_OS_WINDOWS)
+#if defined(TARGET_ARCH_X64) && defined(DART_TARGET_OS_WINDOWS)
   // If struct fits in a single register and size is a power of two, then
   // use a single register and sign extend.
   // Otherwise, pass a pointer to a copy.
@@ -209,7 +209,7 @@ class ArgumentAllocator : public ValueObject {
 
     return AllocateStack(payload_type);
   }
-#endif  // defined(TARGET_ARCH_X64) && defined(TARGET_OS_WINDOWS)
+#endif  // defined(TARGET_ARCH_X64) && defined(DART_TARGET_OS_WINDOWS)
 
 #if defined(TARGET_ARCH_IA32)
   const NativeLocation& AllocateCompound(
@@ -512,7 +512,7 @@ static const NativeLocation& PointerToMemoryResultLocation(
 }
 #endif  // defined(TARGET_ARCH_IA32)
 
-#if defined(TARGET_ARCH_X64) && !defined(TARGET_OS_WINDOWS)
+#if defined(TARGET_ARCH_X64) && !defined(DART_TARGET_OS_WINDOWS)
 static const NativeLocation& CompoundResultLocation(
     Zone* zone,
     const NativeCompoundType& payload_type) {
@@ -564,9 +564,9 @@ static const NativeLocation& CompoundResultLocation(
   }
   return PointerToMemoryResultLocation(zone, payload_type);
 }
-#endif  // defined(TARGET_ARCH_X64) && !defined(TARGET_OS_WINDOWS)
+#endif  // defined(TARGET_ARCH_X64) && !defined(DART_TARGET_OS_WINDOWS)
 
-#if defined(TARGET_ARCH_X64) && defined(TARGET_OS_WINDOWS)
+#if defined(TARGET_ARCH_X64) && defined(DART_TARGET_OS_WINDOWS)
 // If struct fits in a single register do that, and sign extend.
 // Otherwise, pass a pointer to memory.
 static const NativeLocation& CompoundResultLocation(
@@ -584,17 +584,17 @@ static const NativeLocation& CompoundResultLocation(
   }
   return PointerToMemoryResultLocation(zone, payload_type);
 }
-#endif  // defined(TARGET_ARCH_X64) && defined(TARGET_OS_WINDOWS)
+#endif  // defined(TARGET_ARCH_X64) && defined(DART_TARGET_OS_WINDOWS)
 
-#if defined(TARGET_ARCH_IA32) && !defined(TARGET_OS_WINDOWS)
+#if defined(TARGET_ARCH_IA32) && !defined(DART_TARGET_OS_WINDOWS)
 static const NativeLocation& CompoundResultLocation(
     Zone* zone,
     const NativeCompoundType& payload_type) {
   return PointerToMemoryResultLocation(zone, payload_type);
 }
-#endif  // defined(TARGET_ARCH_IA32) && !defined(TARGET_OS_WINDOWS)
+#endif  // defined(TARGET_ARCH_IA32) && !defined(DART_TARGET_OS_WINDOWS)
 
-#if defined(TARGET_ARCH_IA32) && defined(TARGET_OS_WINDOWS)
+#if defined(TARGET_ARCH_IA32) && defined(DART_TARGET_OS_WINDOWS)
 // Windows uses up to two return registers, while Linux does not.
 static const NativeLocation& CompoundResultLocation(
     Zone* zone,
@@ -615,7 +615,7 @@ static const NativeLocation& CompoundResultLocation(
   }
   return PointerToMemoryResultLocation(zone, payload_type);
 }
-#endif  // defined(TARGET_ARCH_IA32) && defined(TARGET_OS_WINDOWS)
+#endif  // defined(TARGET_ARCH_IA32) && defined(DART_TARGET_OS_WINDOWS)
 
 #if defined(TARGET_ARCH_ARM)
 // Arm passes homogenous float return values in FPU registers and small
diff --git a/runtime/vm/compiler/ffi/native_calling_convention_test.cc b/runtime/vm/compiler/ffi/native_calling_convention_test.cc
index 1d1ae2801f6..328c0ca8e9f 100644
--- a/runtime/vm/compiler/ffi/native_calling_convention_test.cc
+++ b/runtime/vm/compiler/ffi/native_calling_convention_test.cc
@@ -586,7 +586,7 @@ UNIT_TEST_CASE_WITH_ZONE(NativeCallingConvention_regress46127) {
       RunSignatureTest(Z, "regress46127", arguments, struct_type);
 
 #if defined(TARGET_ARCH_IA32) &&                                               \
-    (defined(TARGET_OS_ANDROID) || defined(TARGET_OS_LINUX))
+    (defined(DART_TARGET_OS_ANDROID) || defined(DART_TARGET_OS_LINUX))
   // We must count the result pointer passed on the stack as well.
   EXPECT_EQ(4, native_calling_convention.StackTopInBytes());
 #else
@@ -610,7 +610,7 @@ UNIT_TEST_CASE_WITH_ZONE(NativeCallingConvention_struct12bytesFloatx6) {
   const auto& struct_type = NativeStructType::FromNativeTypes(Z, member_types);
 
 #if defined(TARGET_ARCH_ARM64) &&                                              \
-    (defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS))
+    (defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS))
   EXPECT_EQ(4, struct_type.AlignmentInBytesStack());
 #endif
 
diff --git a/runtime/vm/compiler/ffi/native_type.cc b/runtime/vm/compiler/ffi/native_type.cc
index 686816c10ff..b1f8d8c5808 100644
--- a/runtime/vm/compiler/ffi/native_type.cc
+++ b/runtime/vm/compiler/ffi/native_type.cc
@@ -174,7 +174,7 @@ NativeStructType& NativeStructType::FromNativeTypes(Zone* zone,
   // If this struct is passed on the stack, it should be aligned to the largest
   // alignment of its members when passing those members on the stack.
   intptr_t alignment_stack = kAtLeast1ByteAligned;
-#if (defined(TARGET_OS_MACOS_IOS) || defined(TARGET_OS_MACOS)) &&              \
+#if (defined(DART_TARGET_OS_MACOS_IOS) || defined(DART_TARGET_OS_MACOS)) &&    \
     defined(TARGET_ARCH_ARM64)
   // On iOS64 and MacOS arm64 stack values can be less aligned than wordSize,
   // which deviates from the arm64 ABI.
diff --git a/runtime/vm/compiler/ffi/unit_test.cc b/runtime/vm/compiler/ffi/unit_test.cc
index 044b398700b..b58e59f7c3c 100644
--- a/runtime/vm/compiler/ffi/unit_test.cc
+++ b/runtime/vm/compiler/ffi/unit_test.cc
@@ -20,15 +20,15 @@ const char* kArch = "ia32";
 const char* kArch = "x64";
 #endif
 
-#if defined(TARGET_OS_ANDROID)
+#if defined(DART_TARGET_OS_ANDROID)
 const char* kOs = "android";
-#elif defined(TARGET_OS_MACOS_IOS)
+#elif defined(DART_TARGET_OS_MACOS_IOS)
 const char* kOs = "ios";
-#elif defined(TARGET_OS_LINUX)
+#elif defined(DART_TARGET_OS_LINUX)
 const char* kOs = "linux";
-#elif defined(TARGET_OS_MACOS)
+#elif defined(DART_TARGET_OS_MACOS)
 const char* kOs = "macos";
-#elif defined(TARGET_OS_WINDOWS)
+#elif defined(DART_TARGET_OS_WINDOWS)
 const char* kOs = "win";
 #endif
 
diff --git a/runtime/vm/compiler/stub_code_compiler_arm.cc b/runtime/vm/compiler/stub_code_compiler_arm.cc
index ce2faf5fb4f..8b831c34bc4 100644
--- a/runtime/vm/compiler/stub_code_compiler_arm.cc
+++ b/runtime/vm/compiler/stub_code_compiler_arm.cc
@@ -1226,7 +1226,7 @@ void StubCodeCompiler::GenerateInvokeDartCodeStub(Assembler* assembler) {
 
   // target::frame_layout.exit_link_slot_from_entry_fp must be kept in sync
   // with the code below.
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
   ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -27);
 #else
   ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -28);
diff --git a/runtime/vm/compiler/stub_code_compiler_arm64.cc b/runtime/vm/compiler/stub_code_compiler_arm64.cc
index 451a41fae7e..4d92ced76cb 100644
--- a/runtime/vm/compiler/stub_code_compiler_arm64.cc
+++ b/runtime/vm/compiler/stub_code_compiler_arm64.cc
@@ -1343,7 +1343,7 @@ void StubCodeCompiler::GenerateInvokeDartCodeStub(Assembler* assembler) {
   __ ldr(TMP, Address(R3, target::Thread::invoke_dart_code_stub_offset()));
   __ Push(TMP);
 
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
   __ str(R18, Address(R3, target::Thread::saved_shadow_call_stack_offset()));
 #elif defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
@@ -1378,7 +1378,7 @@ void StubCodeCompiler::GenerateInvokeDartCodeStub(Assembler* assembler) {
   __ StoreToOffset(ZR, THR, target::Thread::top_exit_frame_info_offset());
   // target::frame_layout.exit_link_slot_from_entry_fp must be kept in sync
   // with the code below.
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
   ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -24);
 #else
   ASSERT(target::frame_layout.exit_link_slot_from_entry_fp == -23);
@@ -3068,7 +3068,7 @@ void StubCodeCompiler::GenerateJumpToFrameStub(Assembler* assembler) {
   __ mov(FP, R2);                 // Frame_pointer.
   __ mov(THR, R3);
   __ SetupCSPFromThread(THR);
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
   __ ldr(R18, Address(THR, target::Thread::saved_shadow_call_stack_offset()));
 #elif defined(USING_SHADOW_CALL_STACK)
 #error Unimplemented
diff --git a/runtime/vm/compiler/stub_code_compiler_x64.cc b/runtime/vm/compiler/stub_code_compiler_x64.cc
index a3c3821dc22..71c094ce6ff 100644
--- a/runtime/vm/compiler/stub_code_compiler_x64.cc
+++ b/runtime/vm/compiler/stub_code_compiler_x64.cc
@@ -121,7 +121,7 @@ void StubCodeCompiler::GenerateCallToRuntimeStub(Assembler* assembler) {
           Immediate(1 * target::kWordSize));  // Retval is next to 1st argument.
   __ movq(Address(RSP, retval_offset),
           RAX);  // Set retval in target::NativeArguments.
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
   ASSERT(target::NativeArguments::StructSize() >
          CallingConventions::kRegisterTransferLimit);
   __ movq(CallingConventions::kArg1Reg, RSP);
diff --git a/runtime/vm/constants_arm.cc b/runtime/vm/constants_arm.cc
index 19034276ad8..03e790f8e0c 100644
--- a/runtime/vm/constants_arm.cc
+++ b/runtime/vm/constants_arm.cc
@@ -13,7 +13,7 @@ namespace dart {
 using dart::bit_cast;
 
 const char* const cpu_reg_names[kNumberOfCpuRegisters] = {
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
     "r0", "r1", "r2",  "r3",  "r4", "pp", "r6", "fp",
     "r8", "r9", "thr", "r11", "ip", "sp", "lr", "pc",
 #else
diff --git a/runtime/vm/constants_arm.h b/runtime/vm/constants_arm.h
index a5f9f94d9b2..00f567090aa 100644
--- a/runtime/vm/constants_arm.h
+++ b/runtime/vm/constants_arm.h
@@ -99,7 +99,7 @@ enum Register {
   kNoRegister = -1,  // Signals an illegal register.
 
 // Aliases.
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
   FP = R7,
   NOTFP = R11,
 #else
@@ -505,7 +505,7 @@ const RegList kAllCpuRegistersList = 0xFFFF;
 // C++ ABI call registers.
 const RegList kAbiArgumentCpuRegs =
     (1 << R0) | (1 << R1) | (1 << R2) | (1 << R3);
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
 const RegList kAbiPreservedCpuRegs =
     (1 << R4) | (1 << R5) | (1 << R6) | (1 << R8) | (1 << R10) | (1 << R11);
 const int kAbiPreservedCpuRegCount = 6;
@@ -532,7 +532,7 @@ const intptr_t kStoreBufferWrapperSize = 24;
 // Registers available to Dart that are not preserved by runtime calls.
 const RegList kDartVolatileCpuRegs =
     kDartAvailableCpuRegs & ~kAbiPreservedCpuRegs;
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
 const int kDartVolatileCpuRegCount = 6;
 #else
 const int kDartVolatileCpuRegCount = 5;
@@ -572,7 +572,7 @@ class CallingConventions {
       kAlignedToWordSizeBut8AlignedTo8;
 
   // How fields in compounds are aligned.
-#if defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS_IOS)
   static constexpr AlignmentStrategy kFieldAlignment =
       kAlignedToValueSizeBut8AlignedTo4;
 #else
diff --git a/runtime/vm/constants_arm64.h b/runtime/vm/constants_arm64.h
index 61f2c4a28fc..4700efa21e7 100644
--- a/runtime/vm/constants_arm64.h
+++ b/runtime/vm/constants_arm64.h
@@ -356,7 +356,7 @@ const RegList kAllCpuRegistersList = 0xFFFFFFFF;
 // C++ ABI call registers.
 const RegList kAbiArgumentCpuRegs =
     R(R0) | R(R1) | R(R2) | R(R3) | R(R4) | R(R5) | R(R6) | R(R7);
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
 // We rely on R18 not being touched by Dart generated assembly or stubs at all.
 // We rely on that any calls into C++ also preserve R18.
 const RegList kAbiPreservedCpuRegs = R(R18) | R(R19) | R(R20) | R(R21) |
@@ -433,7 +433,7 @@ class CallingConventions {
       kAlignedToWordSize;
 
   // How stack arguments are aligned.
-#if defined(TARGET_OS_MACOS_IOS) || defined(TARGET_OS_MACOS)
+#if defined(DART_TARGET_OS_MACOS_IOS) || defined(DART_TARGET_OS_MACOS)
   // > Function arguments may consume slots on the stack that are not multiples
   // > of 8 bytes.
   // https://developer.apple.com/documentation/xcode/writing_arm64_code_for_apple_platforms
@@ -449,7 +449,7 @@ class CallingConventions {
 
   // Whether 1 or 2 byte-sized arguments or return values are passed extended
   // to 4 bytes.
-#if defined(TARGET_OS_MACOS_IOS) || defined(TARGET_OS_MACOS)
+#if defined(DART_TARGET_OS_MACOS_IOS) || defined(DART_TARGET_OS_MACOS)
   static constexpr ExtensionStrategy kReturnRegisterExtension = kExtendedTo4;
   static constexpr ExtensionStrategy kArgumentRegisterExtension = kExtendedTo4;
 #else
diff --git a/runtime/vm/constants_ia32.h b/runtime/vm/constants_ia32.h
index b83e1966699..e7276430011 100644
--- a/runtime/vm/constants_ia32.h
+++ b/runtime/vm/constants_ia32.h
@@ -345,7 +345,7 @@ class CallingConventions {
       kAlignedToWordSize;
 
   // How fields in compounds are aligned.
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
   static constexpr AlignmentStrategy kFieldAlignment = kAlignedToValueSize;
 #else
   static constexpr AlignmentStrategy kFieldAlignment =
diff --git a/runtime/vm/constants_x64.cc b/runtime/vm/constants_x64.cc
index 6312a546f90..b80a77a5b49 100644
--- a/runtime/vm/constants_x64.cc
+++ b/runtime/vm/constants_x64.cc
@@ -18,7 +18,7 @@ const char* const fpu_reg_names[kNumberOfXmmRegisters] = {
     "xmm0", "xmm1", "xmm2",  "xmm3",  "xmm4",  "xmm5",  "xmm6",  "xmm7",
     "xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15"};
 
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
 const Register CallingConventions::ArgumentRegisters[] = {
     CallingConventions::kArg1Reg, CallingConventions::kArg2Reg,
     CallingConventions::kArg3Reg, CallingConventions::kArg4Reg};
diff --git a/runtime/vm/constants_x64.h b/runtime/vm/constants_x64.h
index 7a3c9b781e2..6e7c80bde11 100644
--- a/runtime/vm/constants_x64.h
+++ b/runtime/vm/constants_x64.h
@@ -354,7 +354,7 @@ enum ScaleFactor {
 
 class CallingConventions {
  public:
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
   static const Register kArg1Reg = RCX;
   static const Register kArg2Reg = RDX;
   static const Register kArg3Reg = R8;
diff --git a/runtime/vm/cpu_arm.cc b/runtime/vm/cpu_arm.cc
index f5f806a0e72..ac65f6d042a 100644
--- a/runtime/vm/cpu_arm.cc
+++ b/runtime/vm/cpu_arm.cc
@@ -14,7 +14,7 @@
 #include "vm/object.h"
 #include "vm/simulator.h"
 
-#if defined(HOST_OS_IOS)
+#if defined(DART_HOST_OS_IOS)
 #include <libkern/OSCacheControl.h>
 #endif
 
@@ -57,7 +57,7 @@ DEFINE_FLAG(bool,
             "Use integer division instruction if supported");
 
 #if defined(TARGET_HOST_MISMATCH)
-#if defined(TARGET_OS_ANDROID) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_ANDROID) || defined(DART_TARGET_OS_MACOS_IOS)
 DEFINE_FLAG(bool, sim_use_hardfp, false, "Use the hardfp ABI.");
 #else
 DEFINE_FLAG(bool, sim_use_hardfp, true, "Use the hardfp ABI.");
@@ -81,7 +81,7 @@ void CPU::FlushICache(uword start, uword size) {
 // On iOS we use sys_icache_invalidate from Darwin. See:
 //
 // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/sys_icache_invalidate.3.html
-#if defined(HOST_OS_IOS)
+#if defined(DART_HOST_OS_IOS)
   sys_icache_invalidate(reinterpret_cast<void*>(start), size);
 #elif defined(__linux__) && !defined(ANDROID)
   extern void __clear_cache(char*, char*);
@@ -115,7 +115,7 @@ bool HostCPUFeatures::initialized_ = false;
 #endif
 
 #if !defined(TARGET_HOST_MISMATCH)
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
 void HostCPUFeatures::Init() {
   // TODO(24743): Actually check the CPU features and fail if we're missing
   // something assumed in a precompiled snapshot.
@@ -130,7 +130,7 @@ void HostCPUFeatures::Init() {
   initialized_ = true;
 #endif
 }
-#else  // HOST_OS_IOS
+#else  // DART_HOST_OS_IOS
 void HostCPUFeatures::Init() {
   bool is_arm64 = false;
   CpuInfo::Init();
@@ -171,7 +171,7 @@ void HostCPUFeatures::Init() {
       CpuInfo::FieldContains(kCpuInfoHardware, "Marvell Armada 370/XP");
   bool is_virtual_machine =
       CpuInfo::FieldContains(kCpuInfoHardware, "Dummy Virtual Machine");
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
   bool is_android = true;
 #else
   bool is_android = false;
@@ -213,7 +213,7 @@ void HostCPUFeatures::Init() {
   initialized_ = true;
 #endif
 }
-#endif  // HOST_OS_IOS
+#endif  // DART_HOST_OS_IOS
 
 void HostCPUFeatures::Cleanup() {
   DEBUG_ASSERT(initialized_);
diff --git a/runtime/vm/cpu_arm64.cc b/runtime/vm/cpu_arm64.cc
index df0f48be466..e27ac58d59e 100644
--- a/runtime/vm/cpu_arm64.cc
+++ b/runtime/vm/cpu_arm64.cc
@@ -12,7 +12,7 @@
 #include "vm/simulator.h"
 
 #if !defined(USING_SIMULATOR)
-#if !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_FUCHSIA)
 #include <sys/syscall.h>
 #else
 #include <zircon/syscalls.h>
@@ -20,7 +20,7 @@
 #include <unistd.h>
 #endif
 
-#if defined(HOST_OS_MACOS) || defined(HOST_OS_IOS)
+#if defined(DART_HOST_OS_MACOS) || defined(DART_HOST_OS_IOS)
 #include <libkern/OSCacheControl.h>
 #endif
 
@@ -42,14 +42,14 @@ void CPU::FlushICache(uword start, uword size) {
 // On iOS we use sys_icache_invalidate from Darwin. See:
 //
 // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/sys_icache_invalidate.3.html
-#if defined(HOST_OS_MACOS) || defined(HOST_OS_IOS)
+#if defined(DART_HOST_OS_MACOS) || defined(DART_HOST_OS_IOS)
   sys_icache_invalidate(reinterpret_cast<void*>(start), size);
-#elif defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX)
+#elif defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
   extern void __clear_cache(char*, char*);
   char* beg = reinterpret_cast<char*>(start);
   char* end = reinterpret_cast<char*>(start + size);
   ::__clear_cache(beg, end);
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
   zx_status_t result = zx_cache_flush(reinterpret_cast<const void*>(start),
                                       size, ZX_CACHE_FLUSH_INSN);
   ASSERT(result == ZX_OK);
diff --git a/runtime/vm/cpuid.cc b/runtime/vm/cpuid.cc
index dddd15a9f13..0541712b5e6 100644
--- a/runtime/vm/cpuid.cc
+++ b/runtime/vm/cpuid.cc
@@ -3,12 +3,12 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if !defined(HOST_OS_MACOS)
+#if !defined(DART_HOST_OS_MACOS)
 #include "vm/cpuid.h"
 
 #if defined(HOST_ARCH_IA32) || defined(HOST_ARCH_X64)
 // GetCpuId() on Windows, __get_cpuid() on Linux
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #include <intrin.h>  // NOLINT
 #else
 #include <cpuid.h>  // NOLINT
@@ -28,7 +28,7 @@ const char* CpuId::brand_string_ = nullptr;
 #if defined(HOST_ARCH_IA32) || defined(HOST_ARCH_X64)
 
 void CpuId::GetCpuId(int32_t level, uint32_t info[4]) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   // The documentation for __cpuid is at:
   // http://msdn.microsoft.com/en-us/library/hskdteyh(v=vs.90).aspx
   __cpuid(reinterpret_cast<int*>(info), level);
@@ -127,4 +127,4 @@ const char* CpuId::field(CpuInfoIndices idx) {
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64)
 }  // namespace dart
 
-#endif  // !defined(HOST_OS_MACOS)
+#endif  // !defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/cpuid.h b/runtime/vm/cpuid.h
index 99f4f34c808..abb4fdc0725 100644
--- a/runtime/vm/cpuid.h
+++ b/runtime/vm/cpuid.h
@@ -6,7 +6,7 @@
 #define RUNTIME_VM_CPUID_H_
 
 #include "vm/globals.h"
-#if !defined(HOST_OS_MACOS)
+#if !defined(DART_HOST_OS_MACOS)
 #include "vm/allocation.h"
 #include "vm/cpuinfo.h"
 
@@ -48,5 +48,5 @@ class CpuId : public AllStatic {
 
 }  // namespace dart
 
-#endif  // !defined(HOST_OS_MACOS)
+#endif  // !defined(DART_HOST_OS_MACOS)
 #endif  // RUNTIME_VM_CPUID_H_
diff --git a/runtime/vm/cpuinfo_android.cc b/runtime/vm/cpuinfo_android.cc
index 0807dfd2fdc..8c34f61408f 100644
--- a/runtime/vm/cpuinfo_android.cc
+++ b/runtime/vm/cpuinfo_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "vm/cpuinfo.h"
 #include "vm/proccpuinfo.h"
@@ -58,4 +58,4 @@ bool CpuInfo::HasField(const char* field) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/cpuinfo_fuchsia.cc b/runtime/vm/cpuinfo_fuchsia.cc
index d5d88cff176..ca197c34dc9 100644
--- a/runtime/vm/cpuinfo_fuchsia.cc
+++ b/runtime/vm/cpuinfo_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "vm/cpuinfo.h"
 
@@ -66,4 +66,4 @@ bool CpuInfo::HasField(const char* field) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/cpuinfo_linux.cc b/runtime/vm/cpuinfo_linux.cc
index 0c4fc99d06c..08621ed41e5 100644
--- a/runtime/vm/cpuinfo_linux.cc
+++ b/runtime/vm/cpuinfo_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "vm/cpuid.h"
 #include "vm/cpuinfo.h"
@@ -94,4 +94,4 @@ bool CpuInfo::HasField(const char* field) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/vm/cpuinfo_macos.cc b/runtime/vm/cpuinfo_macos.cc
index cbc66f48cef..45968135831 100644
--- a/runtime/vm/cpuinfo_macos.cc
+++ b/runtime/vm/cpuinfo_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "vm/cpuinfo.h"
 
@@ -76,4 +76,4 @@ bool CpuInfo::HasField(const char* field) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/cpuinfo_win.cc b/runtime/vm/cpuinfo_win.cc
index 5e5601eeade..2a8ad21f342 100644
--- a/runtime/vm/cpuinfo_win.cc
+++ b/runtime/vm/cpuinfo_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "vm/cpuid.h"
 #include "vm/cpuinfo.h"
@@ -56,4 +56,4 @@ bool CpuInfo::HasField(const char* field) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index b2601a53bd9..2fbb323dac1 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -977,7 +977,7 @@ const char* Dart::FeaturesString(IsolateGroup* isolate_group,
 
 // Generated code must match the host architecture and ABI.
 #if defined(TARGET_ARCH_ARM)
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
     buffer.AddString(" arm-ios");
 #else
     buffer.AddString(" arm-eabi");
@@ -985,7 +985,7 @@ const char* Dart::FeaturesString(IsolateGroup* isolate_group,
     buffer.AddString(TargetCPUFeatures::hardfp_supported() ? " hardfp"
                                                            : " softfp");
 #elif defined(TARGET_ARCH_ARM64)
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
     // See signal handler cheat in Assembler::EnterFrame.
     buffer.AddString(" arm64-fuchsia");
 #else
@@ -994,7 +994,7 @@ const char* Dart::FeaturesString(IsolateGroup* isolate_group,
 #elif defined(TARGET_ARCH_IA32)
     buffer.AddString(" ia32");
 #elif defined(TARGET_ARCH_X64)
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
     buffer.AddString(" x64-win");
 #else
     buffer.AddString(" x64-sysv");
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index db086986b71..756db2786e9 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -6593,7 +6593,7 @@ Dart_CreateAppAOTSnapshotAsAssembly(Dart_StreamingWriteCallback callback,
                                     void* debug_callback_data) {
 #if defined(TARGET_ARCH_IA32)
   return Api::NewError("AOT compilation is not supported on IA32.");
-#elif defined(TARGET_OS_WINDOWS)
+#elif defined(DART_TARGET_OS_WINDOWS)
   return Api::NewError("Assembly generation is not implemented for Windows.");
 #elif !defined(DART_PRECOMPILER)
   return Api::NewError(
@@ -6621,7 +6621,7 @@ DART_EXPORT Dart_Handle Dart_CreateAppAOTSnapshotAsAssemblies(
     Dart_StreamingCloseCallback close_callback) {
 #if defined(TARGET_ARCH_IA32)
   return Api::NewError("AOT compilation is not supported on IA32.");
-#elif defined(TARGET_OS_WINDOWS)
+#elif defined(DART_TARGET_OS_WINDOWS)
   return Api::NewError("Assembly generation is not implemented for Windows.");
 #elif !defined(DART_PRECOMPILER)
   return Api::NewError(
@@ -6645,7 +6645,7 @@ Dart_CreateVMAOTSnapshotAsAssembly(Dart_StreamingWriteCallback callback,
                                    void* callback_data) {
 #if defined(TARGET_ARCH_IA32)
   return Api::NewError("AOT compilation is not supported on IA32.");
-#elif defined(TARGET_OS_WINDOWS)
+#elif defined(DART_TARGET_OS_WINDOWS)
   return Api::NewError("Assembly generation is not implemented for Windows.");
 #elif !defined(DART_PRECOMPILER)
   return Api::NewError(
diff --git a/runtime/vm/dwarf.cc b/runtime/vm/dwarf.cc
index 53d6b39faf0..000bab4cf9e 100644
--- a/runtime/vm/dwarf.cc
+++ b/runtime/vm/dwarf.cc
@@ -778,7 +778,7 @@ static const char* ConvertResolvedURI(const char* str) {
   const intptr_t len = strlen(str);
   if (len > kResolvedFileRootLen &&
       strncmp(str, kResolvedFileRoot, kResolvedFileRootLen) == 0) {
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
     return str + kResolvedFileRootLen;  // Strip off the entire prefix.
 #else
     return str + kResolvedFileRootLen - 1;  // Leave a '/' on the front.
diff --git a/runtime/vm/globals.h b/runtime/vm/globals.h
index d7426c44fa2..d3ac9abe058 100644
--- a/runtime/vm/globals.h
+++ b/runtime/vm/globals.h
@@ -108,7 +108,8 @@ const intptr_t kDefaultMaxOldGenHeapSize = (kWordSize <= 4) ? 1536 : 30720;
 #define NOT_IN_PRECOMPILED_RUNTIME(code) code
 #endif  // defined(DART_PRECOMPILED_RUNTIME)
 
-#if !defined(PRODUCT) || defined(HOST_OS_FUCHSIA) || defined(TARGET_OS_FUCHSIA)
+#if !defined(PRODUCT) || defined(DART_HOST_OS_FUCHSIA) ||                      \
+    defined(DART_TARGET_OS_FUCHSIA)
 #define SUPPORT_TIMELINE 1
 #endif
 
@@ -156,7 +157,7 @@ typedef uword cpp_vtable;
 
 // When using GCC we can use GCC attributes to ensure that certain
 // constants are 8 or 16 byte aligned.
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #define ALIGN8 __declspec(align(8))
 #define ALIGN16 __declspec(align(16))
 #else
@@ -172,7 +173,7 @@ static const uword kZapUninitializedWord = 0xabababababababab;
 #endif
 
 // Macros to get the contents of the fp register.
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 // clang-format off
 #if defined(HOST_ARCH_IA32)
@@ -188,13 +189,13 @@ static const uword kZapUninitializedWord = 0xabababababababab;
 #error Unknown host architecture.
 #endif
 
-#else  // !defined(HOST_OS_WINDOWS))
+#else  // !defined(DART_HOST_OS_WINDOWS))
 
 // Assume GCC-compatible builtins.
 #define COPY_FP_REGISTER(fp)                                                   \
   fp = reinterpret_cast<uintptr_t>(__builtin_frame_address(0));
 
-#endif  // !defined(HOST_OS_WINDOWS))
+#endif  // !defined(DART_HOST_OS_WINDOWS))
 
 #if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_ARM64) ||                  \
     defined(TARGET_ARCH_X64)
diff --git a/runtime/vm/image_snapshot.cc b/runtime/vm/image_snapshot.cc
index dd693837060..658892bd5f5 100644
--- a/runtime/vm/image_snapshot.cc
+++ b/runtime/vm/image_snapshot.cc
@@ -951,20 +951,20 @@ class DwarfAssemblyStream : public DwarfWriteStream {
 
   // Methods for writing the assembly prologues for various DWARF sections.
   void AbbreviationsPrologue() {
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
     stream_->WriteString(".section __DWARF,__debug_abbrev,regular,debug\n");
-#elif defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) ||                \
-    defined(TARGET_OS_FUCHSIA)
+#elif defined(DART_TARGET_OS_LINUX) || defined(DART_TARGET_OS_ANDROID) ||      \
+    defined(DART_TARGET_OS_FUCHSIA)
     stream_->WriteString(".section .debug_abbrev,\"\"\n");
 #else
     UNIMPLEMENTED();
 #endif
   }
   void DebugInfoPrologue() {
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
     stream_->WriteString(".section __DWARF,__debug_info,regular,debug\n");
-#elif defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) ||                \
-    defined(TARGET_OS_FUCHSIA)
+#elif defined(DART_TARGET_OS_LINUX) || defined(DART_TARGET_OS_ANDROID) ||      \
+    defined(DART_TARGET_OS_FUCHSIA)
     stream_->WriteString(".section .debug_info,\"\"\n");
 #else
     UNIMPLEMENTED();
@@ -973,10 +973,10 @@ class DwarfAssemblyStream : public DwarfWriteStream {
     stream_->Printf("%s:\n", kDebugInfoLabel);
   }
   void LineNumberProgramPrologue() {
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
     stream_->WriteString(".section __DWARF,__debug_line,regular,debug\n");
-#elif defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) ||                \
-    defined(TARGET_OS_FUCHSIA)
+#elif defined(DART_TARGET_OS_LINUX) || defined(DART_TARGET_OS_ANDROID) ||      \
+    defined(DART_TARGET_OS_FUCHSIA)
     stream_->WriteString(".section .debug_line,\"\"\n");
 #else
     UNIMPLEMENTED();
@@ -1131,10 +1131,10 @@ bool AssemblyImageWriter::EnterSection(ProgramSection section,
         current_symbols_ =
             new (zone_) ZoneGrowableArray<Elf::SymbolData>(zone_, 0);
       }
-#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) ||                  \
-    defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_LINUX) || defined(DART_TARGET_OS_ANDROID) ||        \
+    defined(DART_TARGET_OS_FUCHSIA)
       assembly_stream_->WriteString(".section .rodata\n");
-#elif defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#elif defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
       assembly_stream_->WriteString(".const\n");
 #else
       UNIMPLEMENTED();
@@ -1308,7 +1308,7 @@ void AssemblyImageWriter::FrameUnwindPrologue() {
   // newer than late 2016. Can't emit .cfi_value_offset using .cfi_scape
   // because DW_CFA_val_offset uses scaled operand and we don't know what
   // data alignment factor will be choosen by the assembler when emitting CIE.
-#if defined(TARGET_OS_ANDROID)
+#if defined(DART_TARGET_OS_ANDROID)
   // On Android libunwindstack has a bug (b/191113792): it does not push
   // CFA value to the expression stack before evaluating expression given
   // to DW_CFA_expression. We have to workaround this bug by manually pushing
@@ -1331,7 +1331,7 @@ void AssemblyImageWriter::FrameUnwindPrologue() {
 #endif
 
 #elif defined(TARGET_ARCH_ARM)
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
   COMPILE_ASSERT(FP == R7);
   assembly_stream_->WriteString(".cfi_def_cfa r7, 0\n");  // CFA is fp+0
   assembly_stream_->WriteString(".cfi_offset r7, 0\n");  // saved fp is *(CFA+0)
@@ -1347,7 +1347,7 @@ void AssemblyImageWriter::FrameUnwindPrologue() {
   // newer than late 2016. Can't emit .cfi_value_offset using .cfi_scape
   // because DW_CFA_val_offset uses scaled operand and we don't know what
   // data alignment factor will be choosen by the assembler when emitting CIE.
-#if defined(TARGET_OS_ANDROID)
+#if defined(DART_TARGET_OS_ANDROID)
   // On Android libunwindstack has a bug (b/191113792): it does not push
   // CFA value to the expression stack before evaluating expression given
   // to DW_CFA_expression. We have to workaround this bug by manually pushing
@@ -1370,7 +1370,7 @@ void AssemblyImageWriter::FrameUnwindPrologue() {
 #endif
 
 // libunwind on ARM may use .ARM.exidx instead of .debug_frame
-#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
+#if !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_MACOS_IOS)
   COMPILE_ASSERT(FP == R11);
   assembly_stream_->WriteString(".fnstart\n");
   assembly_stream_->WriteString(".save {r11, lr}\n");
@@ -1381,7 +1381,7 @@ void AssemblyImageWriter::FrameUnwindPrologue() {
 
 void AssemblyImageWriter::FrameUnwindEpilogue() {
 #if defined(TARGET_ARCH_ARM)
-#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
+#if !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_MACOS_IOS)
   assembly_stream_->WriteString(".fnend\n");
 #endif
 #endif
diff --git a/runtime/vm/malloc_hooks_unsupported.cc b/runtime/vm/malloc_hooks_unsupported.cc
index d28100f63ac..df3a12b354f 100644
--- a/runtime/vm/malloc_hooks_unsupported.cc
+++ b/runtime/vm/malloc_hooks_unsupported.cc
@@ -10,13 +10,13 @@
 
 #include "vm/json_stream.h"
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 #include <malloc.h>
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include <malloc/malloc.h>
 #endif
 
-#if !defined(HOST_OS_WINDOWS) && !defined(TARGET_OS_IOS)
+#if !defined(DART_HOST_OS_WINDOWS) && !defined(DART_TARGET_OS_MACOS_IOS)
 extern "C" {
 __attribute__((weak)) uintptr_t __sanitizer_get_current_allocated_bytes();
 __attribute__((weak)) uintptr_t __sanitizer_get_heap_size();
@@ -60,7 +60,7 @@ bool MallocHooks::GetStats(intptr_t* used,
                            intptr_t* capacity,
                            const char** implementation) {
 #if !defined(PRODUCT)
-#if !defined(HOST_OS_WINDOWS) && !defined(TARGET_OS_IOS)
+#if !defined(DART_HOST_OS_WINDOWS) && !defined(DART_TARGET_OS_MACOS_IOS)
   if (__sanitizer_get_current_allocated_bytes != nullptr &&
       __sanitizer_get_heap_size != nullptr) {
     *used = __sanitizer_get_current_allocated_bytes();
@@ -69,13 +69,13 @@ bool MallocHooks::GetStats(intptr_t* used,
     return true;
   }
 #endif
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   struct mallinfo info = mallinfo();
   *used = info.uordblks;
   *capacity = *used + info.fordblks;
   *implementation = "unknown";
   return true;
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
   struct mstats stats = mstats();
   *used = stats.bytes_used;
   *capacity = stats.bytes_total;
diff --git a/runtime/vm/native_arguments.h b/runtime/vm/native_arguments.h
index 5b206edba3e..d2df92c20d1 100644
--- a/runtime/vm/native_arguments.h
+++ b/runtime/vm/native_arguments.h
@@ -27,7 +27,7 @@ class Thread;
     uword current_sp = Simulator::Current()->get_register(SPREG);              \
     ASSERT(Utils::IsAligned(current_sp, OS::ActivationFrameAlignment()));      \
   }
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 // The compiler may dynamically align the stack on Windows, so do not check.
 #define CHECK_STACK_ALIGNMENT                                                  \
   {}
diff --git a/runtime/vm/native_symbol_android.cc b/runtime/vm/native_symbol_android.cc
index 9d0c24558a9..d7837e3c990 100644
--- a/runtime/vm/native_symbol_android.cc
+++ b/runtime/vm/native_symbol_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "vm/native_symbol.h"
 #include "vm/os.h"
@@ -68,4 +68,4 @@ void NativeSymbolResolver::AddSymbols(const char* dso_name,
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/native_symbol_fuchsia.cc b/runtime/vm/native_symbol_fuchsia.cc
index 12b924961bb..1cb72a83f74 100644
--- a/runtime/vm/native_symbol_fuchsia.cc
+++ b/runtime/vm/native_symbol_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "platform/memory_sanitizer.h"
 #include "vm/native_symbol.h"
@@ -157,4 +157,4 @@ void NativeSymbolResolver::AddSymbols(const char* dso_name,
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/native_symbol_linux.cc b/runtime/vm/native_symbol_linux.cc
index 158a2afea1e..75578905df4 100644
--- a/runtime/vm/native_symbol_linux.cc
+++ b/runtime/vm/native_symbol_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "platform/memory_sanitizer.h"
 #include "vm/native_symbol.h"
@@ -69,4 +69,4 @@ void NativeSymbolResolver::AddSymbols(const char* dso_name,
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/vm/native_symbol_macos.cc b/runtime/vm/native_symbol_macos.cc
index 262bac552b2..aa1fc6c7d91 100644
--- a/runtime/vm/native_symbol_macos.cc
+++ b/runtime/vm/native_symbol_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "vm/native_symbol.h"
 #include "vm/os.h"
@@ -66,4 +66,4 @@ void NativeSymbolResolver::AddSymbols(const char* dso_name,
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/native_symbol_win.cc b/runtime/vm/native_symbol_win.cc
index 9ddc3a4e6cc..db48485a094 100644
--- a/runtime/vm/native_symbol_win.cc
+++ b/runtime/vm/native_symbol_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "vm/lockers.h"
 #include "vm/native_symbol.h"
@@ -26,7 +26,7 @@ void NativeSymbolResolver::Init() {
 
 // Symbol resolution API's used in this file are not supported
 // when compiled in UWP.
-#ifndef TARGET_OS_WINDOWS_UWP
+#ifndef DART_TARGET_OS_WINDOWS_UWP
   SymSetOptions(SYMOPT_UNDNAME | SYMOPT_DEFERRED_LOADS);
   HANDLE hProcess = GetCurrentProcess();
   if (!SymInitialize(hProcess, NULL, TRUE)) {
@@ -45,7 +45,7 @@ void NativeSymbolResolver::Cleanup() {
     return;
   }
   running_ = false;
-#ifndef TARGET_OS_WINDOWS_UWP
+#ifndef DART_TARGET_OS_WINDOWS_UWP
   HANDLE hProcess = GetCurrentProcess();
   if (!SymCleanup(hProcess)) {
     DWORD error = GetLastError();
@@ -57,7 +57,7 @@ void NativeSymbolResolver::Cleanup() {
 }
 
 char* NativeSymbolResolver::LookupSymbolName(uword pc, uword* start) {
-#ifdef TARGET_OS_WINDOWS_UWP
+#ifdef DART_TARGET_OS_WINDOWS_UWP
   return NULL;
 #else
   static const intptr_t kMaxNameLength = 2048;
@@ -86,7 +86,7 @@ char* NativeSymbolResolver::LookupSymbolName(uword pc, uword* start) {
     *start = pc - displacement;
   }
   return Utils::StrDup(pSymbol->Name);
-#endif  // ifdef TARGET_OS_WINDOWS_UWP
+#endif  // ifdef DART_TARGET_OS_WINDOWS_UWP
 }
 
 void NativeSymbolResolver::FreeSymbolName(char* name) {
@@ -107,4 +107,4 @@ void NativeSymbolResolver::AddSymbols(const char* dso_name,
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/vm/os_android.cc b/runtime/vm/os_android.cc
index 10ad9cf62ba..3a32eecb373 100644
--- a/runtime/vm/os_android.cc
+++ b/runtime/vm/os_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "vm/os.h"
 
@@ -349,4 +349,4 @@ void OS::Exit(int code) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/os_fuchsia.cc b/runtime/vm/os_fuchsia.cc
index 46c430376bc..448a10baa97 100644
--- a/runtime/vm/os_fuchsia.cc
+++ b/runtime/vm/os_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "vm/os.h"
 
@@ -638,4 +638,4 @@ void OS::Exit(int code) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/os_linux.cc b/runtime/vm/os_linux.cc
index 9cbb5076778..5d78dc1ff05 100644
--- a/runtime/vm/os_linux.cc
+++ b/runtime/vm/os_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "vm/os.h"
 
@@ -660,4 +660,4 @@ void OS::Exit(int code) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/vm/os_macos.cc b/runtime/vm/os_macos.cc
index 0a7e5293189..eed635df0d2 100644
--- a/runtime/vm/os_macos.cc
+++ b/runtime/vm/os_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "vm/os.h"
 
@@ -15,7 +15,7 @@
 #include <sys/resource.h>    // NOLINT
 #include <sys/time.h>        // NOLINT
 #include <unistd.h>          // NOLINT
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
 #include <syslog.h>  // NOLINT
 #endif
 
@@ -26,7 +26,7 @@
 namespace dart {
 
 const char* OS::Name() {
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
   return "ios";
 #else
   return "macos";
@@ -126,7 +126,7 @@ int64_t OS::GetCurrentThreadCPUMicrosForTimeline() {
 }
 
 intptr_t OS::ActivationFrameAlignment() {
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
 #if TARGET_ARCH_ARM
   // Even if we generate code that maintains a stronger alignment, we cannot
   // assert the stronger stack alignment because C++ code will not maintain it.
@@ -140,11 +140,11 @@ intptr_t OS::ActivationFrameAlignment() {
 #else
 #error Unimplemented
 #endif
-#else   // HOST_OS_IOS
+#else   // DART_HOST_OS_IOS
   // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI
   // Function Call Guide".
   return 16;
-#endif  // HOST_OS_IOS
+#endif  // DART_HOST_OS_IOS
 }
 
 int OS::NumberOfAvailableProcessors() {
@@ -190,7 +190,7 @@ DART_NOINLINE uintptr_t OS::GetProgramCounter() {
 }
 
 void OS::Print(const char* format, ...) {
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
   va_list args;
   va_start(args, format);
   vsyslog(LOG_INFO, format, args);
@@ -267,7 +267,7 @@ bool OS::StringToInt64(const char* str, int64_t* value) {
 void OS::RegisterCodeObservers() {}
 
 void OS::PrintErr(const char* format, ...) {
-#if HOST_OS_IOS
+#if DART_HOST_OS_IOS
   va_list args;
   va_start(args, format);
   vsyslog(LOG_ERR, format, args);
@@ -312,4 +312,4 @@ void OS::Exit(int code) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/os_thread.h b/runtime/vm/os_thread.h
index edd66f5bbb8..dca500353c5 100644
--- a/runtime/vm/os_thread.h
+++ b/runtime/vm/os_thread.h
@@ -13,20 +13,20 @@
 #include "vm/globals.h"
 
 // On iOS, thread_local requires iOS 9+.
-#if !HOST_OS_IOS
+#if !DART_HOST_OS_IOS
 #define HAS_C11_THREAD_LOCAL 1
 #endif
 
 // Declare the OS-specific types ahead of defining the generic classes.
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 #include "vm/os_thread_android.h"
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
 #include "vm/os_thread_fuchsia.h"
-#elif defined(HOST_OS_LINUX)
+#elif defined(DART_HOST_OS_LINUX)
 #include "vm/os_thread_linux.h"
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include "vm/os_thread_macos.h"
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 #include "vm/os_thread_win.h"
 #else
 #error Unknown target os.
diff --git a/runtime/vm/os_thread_android.cc b/runtime/vm/os_thread_android.cc
index cff837876db..df257e330ab 100644
--- a/runtime/vm/os_thread_android.cc
+++ b/runtime/vm/os_thread_android.cc
@@ -4,7 +4,7 @@
 
 #include "platform/globals.h"  // NOLINT
 
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include "vm/os_thread.h"
 
@@ -490,4 +490,4 @@ void Monitor::NotifyAll() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/os_thread_fuchsia.cc b/runtime/vm/os_thread_fuchsia.cc
index 9108f5dffdf..1eb8a3a0f14 100644
--- a/runtime/vm/os_thread_fuchsia.cc
+++ b/runtime/vm/os_thread_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"  // NOLINT
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "vm/os.h"
 #include "vm/os_thread.h"
@@ -492,4 +492,4 @@ void Monitor::NotifyAll() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/os_thread_linux.cc b/runtime/vm/os_thread_linux.cc
index 053736d9017..167721a67b9 100644
--- a/runtime/vm/os_thread_linux.cc
+++ b/runtime/vm/os_thread_linux.cc
@@ -4,7 +4,7 @@
 
 #include "platform/globals.h"  // NOLINT
 
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include "vm/os_thread.h"
 
@@ -496,4 +496,4 @@ void Monitor::NotifyAll() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/vm/os_thread_macos.cc b/runtime/vm/os_thread_macos.cc
index e24ce128dfb..401fdc79a52 100644
--- a/runtime/vm/os_thread_macos.cc
+++ b/runtime/vm/os_thread_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"  // NOLINT
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include "vm/os_thread.h"
 
@@ -459,4 +459,4 @@ void Monitor::NotifyAll() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/os_thread_win.cc b/runtime/vm/os_thread_win.cc
index 7c2f9b2caef..8b859a83afb 100644
--- a/runtime/vm/os_thread_win.cc
+++ b/runtime/vm/os_thread_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"  // NOLINT
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "vm/growable_array.h"
 #include "vm/lockers.h"
@@ -530,4 +530,4 @@ PIMAGE_TLS_CALLBACK p_thread_callback_dart = OnDartThreadExit;
 #endif  // _WIN64
 }  // extern "C"
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/vm/os_win.cc b/runtime/vm/os_win.cc
index da2d6f7d5a7..3eb9be090ae 100644
--- a/runtime/vm/os_win.cc
+++ b/runtime/vm/os_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "vm/os.h"
 
@@ -348,4 +348,4 @@ void OS::Exit(int code) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/vm/proccpuinfo.cc b/runtime/vm/proccpuinfo.cc
index 6278627086b..066e3f7a5f6 100644
--- a/runtime/vm/proccpuinfo.cc
+++ b/runtime/vm/proccpuinfo.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 
 #include "vm/proccpuinfo.h"
 
@@ -146,4 +146,4 @@ bool ProcCpuInfo::HasField(const char* field) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/proccpuinfo.h b/runtime/vm/proccpuinfo.h
index 02ee2bf176e..ff249d42d2d 100644
--- a/runtime/vm/proccpuinfo.h
+++ b/runtime/vm/proccpuinfo.h
@@ -6,7 +6,7 @@
 #define RUNTIME_VM_PROCCPUINFO_H_
 
 #include "vm/globals.h"
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 
 #include "vm/allocation.h"
 
@@ -29,6 +29,6 @@ class ProcCpuInfo : public AllStatic {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 
 #endif  // RUNTIME_VM_PROCCPUINFO_H_
diff --git a/runtime/vm/profiler.cc b/runtime/vm/profiler.cc
index 568c78a5fcf..532eb63e831 100644
--- a/runtime/vm/profiler.cc
+++ b/runtime/vm/profiler.cc
@@ -797,7 +797,7 @@ static void CopyStackBuffer(Sample* sample, uword sp_addr) {
   }
 }
 
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 // On Windows this code is synchronously executed from the thread interrupter
 // thread. This means we can safely have a static fault_address.
 static uword fault_address = 0;
@@ -826,7 +826,7 @@ static void CollectSample(Isolate* isolate,
                           uword sp,
                           ProfilerCounters* counters) {
   ASSERT(counters != NULL);
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   // Use structured exception handling to trap guard page access on Windows.
   __try {
 #endif
@@ -854,7 +854,7 @@ static void CollectSample(Isolate* isolate,
       sample->SetAt(0, pc);
     }
 
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
     // Use structured exception handling to trap guard page access.
   } __except (GuardPageExceptionFilter(GetExceptionInformation())) {  // NOLINT
     // Sample collection triggered a guard page fault:
@@ -1013,14 +1013,15 @@ void Profiler::DumpStackTrace(void* context) {
     DumpStackTrace(/*for_crash=*/true);
     return;
   }
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_MACOS) ||              \
+    defined(DART_HOST_OS_ANDROID)
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
   mcontext_t mcontext = ucontext->uc_mcontext;
   uword pc = SignalHandler::GetProgramCounter(mcontext);
   uword fp = SignalHandler::GetFramePointer(mcontext);
   uword sp = SignalHandler::GetCStackPointer(mcontext);
   DumpStackTrace(sp, fp, pc, /*for_crash=*/true);
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
   CONTEXT* ctx = reinterpret_cast<CONTEXT*>(context);
 #if defined(HOST_ARCH_IA32)
   uword pc = static_cast<uword>(ctx->Eip);
diff --git a/runtime/vm/profiler_test.cc b/runtime/vm/profiler_test.cc
index 5d6bd682297..1829169ca63 100644
--- a/runtime/vm/profiler_test.cc
+++ b/runtime/vm/profiler_test.cc
@@ -478,8 +478,8 @@ ISOLATE_UNIT_TEST_CASE(Profiler_TrivialRecordAllocation) {
   }
 }
 
-#if defined(DART_USE_TCMALLOC) && defined(HOST_OS_LINUX) && defined(DEBUG) &&  \
-    defined(HOST_ARCH_X64)
+#if defined(DART_USE_TCMALLOC) && defined(DART_HOST_OS_LINUX) &&               \
+    defined(DEBUG) && defined(HOST_ARCH_X64)
 
 DART_NOINLINE static void NativeAllocationSampleHelper(char** result) {
   ASSERT(result != NULL);
@@ -584,7 +584,7 @@ ISOLATE_UNIT_TEST_CASE(Profiler_NativeAllocation) {
       stack_trace_collection_enabled);
   FLAG_profiler_native_memory = enable_malloc_hooks_saved;
 }
-#endif  // defined(DART_USE_TCMALLOC) && defined(HOST_OS_LINUX) &&             \
+#endif  // defined(DART_USE_TCMALLOC) && defined(DART_HOST_OS_LINUX) &&        \
         // defined(DEBUG) && defined(HOST_ARCH_X64)
 
 ISOLATE_UNIT_TEST_CASE(Profiler_ToggleRecordAllocation) {
diff --git a/runtime/vm/runtime_entry.cc b/runtime/vm/runtime_entry.cc
index 2cd5a195b4e..c7305ca34fd 100644
--- a/runtime/vm/runtime_entry.cc
+++ b/runtime/vm/runtime_entry.cc
@@ -3595,7 +3595,7 @@ static Thread* GetThreadForNativeCallback(uword callback_id,
   return thread;
 }
 
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 #pragma intrinsic(_ReturnAddress)
 #endif
 
@@ -3606,7 +3606,7 @@ static Thread* GetThreadForNativeCallback(uword callback_id,
 extern "C" Thread* DLRT_GetThreadForNativeCallback(uword callback_id) {
   CHECK_STACK_ALIGNMENT;
   TRACE_RUNTIME_CALL("GetThreadForNativeCallback %" Pd, callback_id);
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
   void* return_address = _ReturnAddress();
 #else
   void* return_address = __builtin_return_address(0);
diff --git a/runtime/vm/service.cc b/runtime/vm/service.cc
index 804ca501f2e..51d5a000599 100644
--- a/runtime/vm/service.cc
+++ b/runtime/vm/service.cc
@@ -4238,7 +4238,7 @@ static void RequestHeapSnapshot(Thread* thread, JSONStream* js) {
   PrintSuccess(js);
 }
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
 struct VMMapping {
   char path[256];
   size_t size;
@@ -4404,7 +4404,7 @@ static intptr_t GetProcessMemoryUsageHelper(JSONStream* js) {
   }
 
   // On Android, malloc is better labeled by /proc/self/smaps.
-#if !defined(HOST_OS_ANDROID)
+#if !defined(DART_HOST_OS_ANDROID)
   intptr_t used, capacity;
   const char* implementation;
   if (MallocHooks::GetStats(&used, &capacity, &implementation)) {
@@ -4432,7 +4432,7 @@ static intptr_t GetProcessMemoryUsageHelper(JSONStream* js) {
   }
 #endif
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   AddVMMappings(&rss_children);
 #endif
   // TODO(46166): Implement for other operating systems.
diff --git a/runtime/vm/signal_handler.h b/runtime/vm/signal_handler.h
index 41eea90dc59..22821d35fba 100644
--- a/runtime/vm/signal_handler.h
+++ b/runtime/vm/signal_handler.h
@@ -8,10 +8,10 @@
 #include "vm/allocation.h"
 #include "vm/globals.h"
 
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 #include <signal.h>    // NOLINT
 #include <ucontext.h>  // NOLINT
-#elif defined(HOST_OS_ANDROID)
+#elif defined(DART_HOST_OS_ANDROID)
 #include <signal.h>  // NOLINT
 #if !defined(__BIONIC_HAVE_UCONTEXT_T)
 #include <asm/sigcontext.h>  // NOLINT
@@ -25,15 +25,15 @@ typedef struct ucontext {
   uint32_t uc_sigmask;
 } ucontext_t;
 #endif                       // !defined(__BIONIC_HAVE_UCONTEXT_T)
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include <signal.h>        // NOLINT
 #include <sys/ucontext.h>  // NOLINT
-#elif defined(HOST_OS_WINDOWS)
+#elif defined(DART_HOST_OS_WINDOWS)
 // Stub out for windows.
 struct siginfo_t;
 struct mcontext_t;
 struct sigset_t {};
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
 #include <signal.h>    // NOLINT
 #include <ucontext.h>  // NOLINT
 #endif
@@ -42,7 +42,7 @@ struct sigset_t {};
 // work around incorrect Thumb -> ARM transitions. See SignalHandlerTrampoline
 // below for more details.
 #if defined(HOST_ARCH_ARM) &&                                                  \
-    (defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)) &&                    \
+    (defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)) &&          \
     !defined(__thumb__)
 #define USE_SIGNAL_HANDLER_TRAMPOLINE
 #endif
diff --git a/runtime/vm/signal_handler_android.cc b/runtime/vm/signal_handler_android.cc
index cdef00fc363..47c2dedb637 100644
--- a/runtime/vm/signal_handler_android.cc
+++ b/runtime/vm/signal_handler_android.cc
@@ -6,7 +6,7 @@
 #include "vm/instructions.h"
 #include "vm/signal_handler.h"
 #include "vm/simulator.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 namespace dart {
 
@@ -138,4 +138,4 @@ void SignalHandler::Remove() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/signal_handler_fuchsia.cc b/runtime/vm/signal_handler_fuchsia.cc
index a0f0cf1af17..3a2f161994e 100644
--- a/runtime/vm/signal_handler_fuchsia.cc
+++ b/runtime/vm/signal_handler_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "vm/signal_handler.h"
 
@@ -46,4 +46,4 @@ void SignalHandler::Remove() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/signal_handler_linux.cc b/runtime/vm/signal_handler_linux.cc
index a9cb30bcec8..ae75730848e 100644
--- a/runtime/vm/signal_handler_linux.cc
+++ b/runtime/vm/signal_handler_linux.cc
@@ -6,7 +6,7 @@
 #include "vm/instructions.h"
 #include "vm/signal_handler.h"
 #include "vm/simulator.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 namespace dart {
 
@@ -117,4 +117,4 @@ void SignalHandler::Remove() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/vm/signal_handler_macos.cc b/runtime/vm/signal_handler_macos.cc
index 081a947ddb6..71ad84f5cca 100644
--- a/runtime/vm/signal_handler_macos.cc
+++ b/runtime/vm/signal_handler_macos.cc
@@ -6,7 +6,7 @@
 #include "vm/instructions.h"
 #include "vm/signal_handler.h"
 #include "vm/simulator.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 namespace dart {
 
@@ -113,4 +113,4 @@ void SignalHandler::Remove() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/signal_handler_win.cc b/runtime/vm/signal_handler_win.cc
index f38ba71ab58..254164c3350 100644
--- a/runtime/vm/signal_handler_win.cc
+++ b/runtime/vm/signal_handler_win.cc
@@ -4,7 +4,7 @@
 
 #include "vm/globals.h"
 #include "vm/signal_handler.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 namespace dart {
 
@@ -43,4 +43,4 @@ void SignalHandler::Remove() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/vm/simulator_arm.cc b/runtime/vm/simulator_arm.cc
index a775233a6d0..d17cb92e08e 100644
--- a/runtime/vm/simulator_arm.cc
+++ b/runtime/vm/simulator_arm.cc
@@ -3554,7 +3554,7 @@ int64_t Simulator::Call(int32_t entry,
   int32_t r6_val = get_register(R6);
   int32_t r7_val = get_register(R7);
   int32_t r8_val = get_register(R8);
-#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
+#if !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_MACOS_IOS)
   int32_t r9_val = get_register(R9);
 #endif
   int32_t r10_val = get_register(R10);
@@ -3588,7 +3588,7 @@ int64_t Simulator::Call(int32_t entry,
   set_register(R6, callee_saved_value);
   set_register(R7, callee_saved_value);
   set_register(R8, callee_saved_value);
-#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
+#if !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_MACOS_IOS)
   set_register(R9, callee_saved_value);
 #endif
   set_register(R10, callee_saved_value);
@@ -3616,7 +3616,7 @@ int64_t Simulator::Call(int32_t entry,
   ASSERT(callee_saved_value == get_register(R6));
   ASSERT(callee_saved_value == get_register(R7));
   ASSERT(callee_saved_value == get_register(R8));
-#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
+#if !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_MACOS_IOS)
   ASSERT(callee_saved_value == get_register(R9));
 #endif
   ASSERT(callee_saved_value == get_register(R10));
@@ -3639,7 +3639,7 @@ int64_t Simulator::Call(int32_t entry,
   set_register(R6, r6_val);
   set_register(R7, r7_val);
   set_register(R8, r8_val);
-#if !defined(TARGET_OS_MACOS) && !defined(TARGET_OS_MACOS_IOS)
+#if !defined(DART_TARGET_OS_MACOS) && !defined(DART_TARGET_OS_MACOS_IOS)
   set_register(R9, r9_val);
 #endif
   set_register(R10, r10_val);
diff --git a/runtime/vm/simulator_arm64.cc b/runtime/vm/simulator_arm64.cc
index 83f65d7dc03..f62ce3bf78c 100644
--- a/runtime/vm/simulator_arm64.cc
+++ b/runtime/vm/simulator_arm64.cc
@@ -950,7 +950,7 @@ void Simulator::set_register(Instr* instr,
                              R31Type r31t) {
   // Register is in range.
   ASSERT((reg >= 0) && (reg < kNumberOfCpuRegisters));
-#if !defined(TARGET_OS_FUCHSIA)
+#if !defined(DART_TARGET_OS_FUCHSIA)
   ASSERT(instr == NULL || reg != R18);  // R18 is globally reserved on iOS.
 #endif
 
@@ -2711,7 +2711,7 @@ void Simulator::DecodeMiscDP3Source(Instr* instr) {
     // Format(instr, "smulh 'rd, 'rn, 'rm");
     const int64_t rn_val = get_register(rn, R31IsZR);
     const int64_t rm_val = get_register(rm, R31IsZR);
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
     // Visual Studio does not support __int128.
     int64_t alu_out;
     Multiply128(rn_val, rm_val, &alu_out);
@@ -2719,7 +2719,7 @@ void Simulator::DecodeMiscDP3Source(Instr* instr) {
     const __int128 res =
         static_cast<__int128>(rn_val) * static_cast<__int128>(rm_val);
     const int64_t alu_out = static_cast<int64_t>(res >> 64);
-#endif  // HOST_OS_WINDOWS
+#endif  // DART_HOST_OS_WINDOWS
     set_register(instr, rd, alu_out, R31IsZR);
   } else if ((instr->Bits(29, 3) == 4) && (instr->Bits(21, 3) == 6) &&
              (instr->Bit(15) == 0)) {
@@ -2727,7 +2727,7 @@ void Simulator::DecodeMiscDP3Source(Instr* instr) {
     // Format(instr, "umulh 'rd, 'rn, 'rm");
     const uint64_t rn_val = get_register(rn, R31IsZR);
     const uint64_t rm_val = get_register(rm, R31IsZR);
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
     // Visual Studio does not support __int128.
     uint64_t alu_out;
     UnsignedMultiply128(rn_val, rm_val, &alu_out);
@@ -2735,7 +2735,7 @@ void Simulator::DecodeMiscDP3Source(Instr* instr) {
     const unsigned __int128 res = static_cast<unsigned __int128>(rn_val) *
                                   static_cast<unsigned __int128>(rm_val);
     const uint64_t alu_out = static_cast<uint64_t>(res >> 64);
-#endif  // HOST_OS_WINDOWS
+#endif  // DART_HOST_OS_WINDOWS
     set_register(instr, rd, alu_out, R31IsZR);
   } else if ((instr->Bits(29, 3) == 4) && (instr->Bit(15) == 0)) {
     if (instr->Bits(21, 3) == 5) {
diff --git a/runtime/vm/stack_frame.cc b/runtime/vm/stack_frame.cc
index b0831552a8d..e9fc6f7b2ed 100644
--- a/runtime/vm/stack_frame.cc
+++ b/runtime/vm/stack_frame.cc
@@ -146,7 +146,7 @@ bool StackFrame::IsStubFrame() const {
   }
 
   ASSERT(!(IsEntryFrame() || IsExitFrame()));
-#if !defined(HOST_OS_WINDOWS) && !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_WINDOWS) && !defined(DART_HOST_OS_FUCHSIA)
   // On Windows and Fuchsia, the profiler calls this from a separate thread
   // where Thread::Current() is NULL, so we cannot create a NoSafepointScope.
   NoSafepointScope no_safepoint;
@@ -335,7 +335,7 @@ CodePtr StackFrame::LookupDartCode() const {
 // We add a no gc scope to ensure that the code below does not trigger
 // a GC as we are handling raw object references here. It is possible
 // that the code is called while a GC is in progress, that is ok.
-#if !defined(HOST_OS_WINDOWS) && !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_WINDOWS) && !defined(DART_HOST_OS_FUCHSIA)
   // On Windows and Fuchsia, the profiler calls this from a separate thread
   // where Thread::Current() is NULL, so we cannot create a NoSafepointScope.
   NoSafepointScope no_safepoint;
diff --git a/runtime/vm/stack_frame_arm.h b/runtime/vm/stack_frame_arm.h
index e79cc9c4f5a..8b5a5d36132 100644
--- a/runtime/vm/stack_frame_arm.h
+++ b/runtime/vm/stack_frame_arm.h
@@ -49,7 +49,7 @@ static const int kCallerSpSlotFromFp = 2;
 static const int kLastParamSlotFromEntrySp = 0;
 
 // Entry and exit frame layout.
-#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+#if defined(DART_TARGET_OS_MACOS) || defined(DART_TARGET_OS_MACOS_IOS)
 static const int kExitLinkSlotFromEntryFp = -27;
 COMPILE_ASSERT(kAbiPreservedCpuRegCount == 6);
 COMPILE_ASSERT(kAbiPreservedFpuRegCount == 4);
diff --git a/runtime/vm/stack_frame_arm64.h b/runtime/vm/stack_frame_arm64.h
index a487e67891c..a6d1e9d8e9d 100644
--- a/runtime/vm/stack_frame_arm64.h
+++ b/runtime/vm/stack_frame_arm64.h
@@ -49,7 +49,7 @@ static const int kCallerSpSlotFromFp = 2;
 static const int kLastParamSlotFromEntrySp = 0;
 
 // Entry and exit frame layout.
-#if defined(TARGET_OS_FUCHSIA)
+#if defined(DART_TARGET_OS_FUCHSIA)
 static const int kExitLinkSlotFromEntryFp = -24;
 COMPILE_ASSERT(kAbiPreservedCpuRegCount == 11);
 #else
diff --git a/runtime/vm/stack_frame_x64.h b/runtime/vm/stack_frame_x64.h
index fd6176b0f3c..d924db1ccd3 100644
--- a/runtime/vm/stack_frame_x64.h
+++ b/runtime/vm/stack_frame_x64.h
@@ -52,11 +52,11 @@ static const int kCallerSpSlotFromFp = 2;
 static const int kLastParamSlotFromEntrySp = 1;  // Skip return address.
 
 // Entry and exit frame layout.
-#if defined(TARGET_OS_WINDOWS)
+#if defined(DART_TARGET_OS_WINDOWS)
 static const int kExitLinkSlotFromEntryFp = -33;
 #else
 static const int kExitLinkSlotFromEntryFp = -11;
-#endif  // defined(TARGET_OS_WINDOWS)
+#endif  // defined(DART_TARGET_OS_WINDOWS)
 
 // For FFI native -> Dart callbacks, the number of stack slots between arguments
 // passed on stack and arguments saved in callback prologue. 2 = return adddress
diff --git a/runtime/vm/tagged_pointer.h b/runtime/vm/tagged_pointer.h
index cbf9a354f0d..dac584b4b7f 100644
--- a/runtime/vm/tagged_pointer.h
+++ b/runtime/vm/tagged_pointer.h
@@ -194,7 +194,7 @@ class ObjectPtr {
   uword heap_base() const {
     // TODO(rmacnak): Why does Windows have trouble linking GetClassId used
     // here?
-#if !defined(HOST_OS_WINDOWS)
+#if !defined(DART_HOST_OS_WINDOWS)
     ASSERT(IsHeapObject());
     ASSERT(!IsInstructions());
     ASSERT(!IsInstructionsSection());
diff --git a/runtime/vm/thread.h b/runtime/vm/thread.h
index 0f746385969..2d80830add6 100644
--- a/runtime/vm/thread.h
+++ b/runtime/vm/thread.h
@@ -1261,7 +1261,7 @@ class RuntimeCallDeoptScope : public StackResource {
   }
 };
 
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 // Clears the state of the current thread and frees the allocation.
 void WindowsThreadCleanUp();
 #endif
diff --git a/runtime/vm/thread_interrupter_android.cc b/runtime/vm/thread_interrupter_android.cc
index 87eb5fc656e..367fa416afd 100644
--- a/runtime/vm/thread_interrupter_android.cc
+++ b/runtime/vm/thread_interrupter_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_ANDROID)
 
 #include <errno.h>        // NOLINT
 #include <sys/syscall.h>  // NOLINT
@@ -75,4 +75,4 @@ void ThreadInterrupter::RemoveSignalHandler() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID)
+#endif  // defined(DART_HOST_OS_ANDROID)
diff --git a/runtime/vm/thread_interrupter_fuchsia.cc b/runtime/vm/thread_interrupter_fuchsia.cc
index c0f5d5e1a5c..b2955694ae9 100644
--- a/runtime/vm/thread_interrupter_fuchsia.cc
+++ b/runtime/vm/thread_interrupter_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "vm/thread_interrupter.h"
 
@@ -255,4 +255,4 @@ void ThreadInterrupter::RemoveSignalHandler() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/thread_interrupter_linux.cc b/runtime/vm/thread_interrupter_linux.cc
index 04b0686f2d4..300a3dd1468 100644
--- a/runtime/vm/thread_interrupter_linux.cc
+++ b/runtime/vm/thread_interrupter_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_LINUX)
 
 #include <errno.h>  // NOLINT
 
@@ -74,4 +74,4 @@ void ThreadInterrupter::RemoveSignalHandler() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_LINUX)
diff --git a/runtime/vm/thread_interrupter_macos.cc b/runtime/vm/thread_interrupter_macos.cc
index eb89fe75a8a..bc81f93882d 100644
--- a/runtime/vm/thread_interrupter_macos.cc
+++ b/runtime/vm/thread_interrupter_macos.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 
 #include <assert.h>      // NOLINT
 #include <errno.h>       // NOLINT
@@ -95,4 +95,4 @@ void ThreadInterrupter::RemoveSignalHandler() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/thread_interrupter_win.cc b/runtime/vm/thread_interrupter_win.cc
index c862a225279..bfbf5d1e55d 100644
--- a/runtime/vm/thread_interrupter_win.cc
+++ b/runtime/vm/thread_interrupter_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "vm/flags.h"
 #include "vm/os.h"
@@ -118,4 +118,4 @@ void ThreadInterrupter::RemoveSignalHandler() {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)
diff --git a/runtime/vm/timeline.cc b/runtime/vm/timeline.cc
index 74d2ef47710..e57fa3b67e6 100644
--- a/runtime/vm/timeline.cc
+++ b/runtime/vm/timeline.cc
@@ -106,13 +106,13 @@ static TimelineEventRecorder* CreateTimelineRecorder() {
         THR_Print("Using the Systrace timeline recorder.\n");
       }
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
       return new TimelineEventSystraceRecorder();
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
       if (__builtin_available(iOS 12.0, macOS 10.14, *)) {
         return new TimelineEventMacosRecorder();
       }
-#elif defined(HOST_OS_FUCHSIA)
+#elif defined(DART_HOST_OS_FUCHSIA)
       return new TimelineEventFuchsiaRecorder();
 #else
       OS::PrintErr(
@@ -754,13 +754,13 @@ TimelineStream::TimelineStream(const char* name,
                                bool enabled)
     : name_(name),
       fuchsia_name_(fuchsia_name),
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
       enabled_(static_cast<uintptr_t>(true))  // For generated code.
 #else
       enabled_(static_cast<uintptr_t>(enabled))
 #endif
 {
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
   if (__builtin_available(iOS 12.0, macOS 10.14, *)) {
     macos_log_ = os_log_create("Dart", name);
   }
@@ -1086,7 +1086,7 @@ void TimelineEventRecorder::WriteTo(const char* directory) {
 
 int64_t TimelineEventRecorder::GetNextAsyncId() {
   // TODO(johnmccutchan): Gracefully handle wrap around.
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
   return trace_generate_nonce();
 #else
   uint32_t next = static_cast<uint32_t>(async_id_.fetch_add(1u));
diff --git a/runtime/vm/timeline.h b/runtime/vm/timeline.h
index ce3def96aa2..69302aa9231 100644
--- a/runtime/vm/timeline.h
+++ b/runtime/vm/timeline.h
@@ -15,16 +15,16 @@
 #include "vm/os.h"
 #include "vm/os_thread.h"
 
-#if defined(FUCHSIA_SDK) || defined (HOST_OS_FUCHSIA)
+#if defined(FUCHSIA_SDK) || defined(DART_HOST_OS_FUCHSIA)
 #include <lib/trace-engine/context.h>
 #include <lib/trace-engine/instrumentation.h>
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
 #include <os/availability.h>
 #if defined(__MAC_10_14) || defined (__IPHONE_12_0)
-#define HOST_OS_SUPPORTS_SIGNPOST 1
+#define DART_HOST_OS_SUPPORTS_SIGNPOST 1
 #endif
 // signpost.h exists in macOS 10.14, iOS 12 or above
-#if defined(HOST_OS_SUPPORTS_SIGNPOST)
+#if defined(DART_HOST_OS_SUPPORTS_SIGNPOST)
 #include <os/signpost.h>
 #else
 #include <os/log.h>
@@ -77,7 +77,7 @@ class TimelineStream {
   const char* fuchsia_name() const { return fuchsia_name_; }
 
   bool enabled() {
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 #ifdef PRODUCT
     return trace_is_category_enabled(fuchsia_name_);
 #else
@@ -85,7 +85,7 @@ class TimelineStream {
 #endif  // PRODUCT
 #else
     return enabled_ != 0;
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
   }
 
   void set_enabled(bool enabled) { enabled_ = enabled ? 1 : 0; }
@@ -100,9 +100,9 @@ class TimelineStream {
     return OFFSET_OF(TimelineStream, enabled_);
   }
 
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
   trace_site_t* trace_site() { return &trace_site_; }
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
   os_log_t macos_log() { return macos_log_; }
 #endif
 
@@ -114,9 +114,9 @@ class TimelineStream {
   // 0 or 1. If this becomes a BitField, the generated code must be updated.
   uintptr_t enabled_;
 
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
   trace_site_t trace_site_ = {};
-#elif defined(HOST_OS_MACOS)
+#elif defined(DART_HOST_OS_MACOS)
   os_log_t macos_log_ = {};
 #endif
 };
@@ -933,7 +933,7 @@ class TimelineEventPlatformRecorder : public TimelineEventRecorder {
   void CompleteEvent(TimelineEvent* event);
 };
 
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 // A recorder that sends events to Fuchsia's tracing app.
 class TimelineEventFuchsiaRecorder : public TimelineEventPlatformRecorder {
  public:
@@ -946,9 +946,9 @@ class TimelineEventFuchsiaRecorder : public TimelineEventPlatformRecorder {
  private:
   void OnEvent(TimelineEvent* event);
 };
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
 
-#if defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
 // A recorder that writes events to Android Systrace. This class is exposed in
 // this header file only so that PrintSystrace can be visible to
 // timeline_test.cc.
@@ -969,9 +969,9 @@ class TimelineEventSystraceRecorder : public TimelineEventPlatformRecorder {
 
   int systrace_fd_;
 };
-#endif  // defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
 
-#if defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_MACOS)
 // A recorder that sends events to Macos's tracing app. See:
 // https://developer.apple.com/documentation/os/logging?language=objc
 class TimelineEventMacosRecorder : public TimelineEventPlatformRecorder {
@@ -985,7 +985,7 @@ class TimelineEventMacosRecorder : public TimelineEventPlatformRecorder {
  private:
   void OnEvent(TimelineEvent* event) API_AVAILABLE(ios(12.0), macos(10.14));
 };
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
 
 class DartTimelineEventHelpers : public AllStatic {
  public:
diff --git a/runtime/vm/timeline_android.cc b/runtime/vm/timeline_android.cc
index 046d0a2b75f..93e2faad417 100644
--- a/runtime/vm/timeline_android.cc
+++ b/runtime/vm/timeline_android.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_ANDROID) && defined(SUPPORT_TIMELINE)
+#if defined(DART_HOST_OS_ANDROID) && defined(SUPPORT_TIMELINE)
 
 #include <errno.h>
 #include <fcntl.h>
@@ -115,4 +115,4 @@ void TimelineEventSystraceRecorder::OnEvent(TimelineEvent* event) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID) && !defined(PRODUCT)
+#endif  // defined(DART_HOST_OS_ANDROID) && !defined(PRODUCT)
diff --git a/runtime/vm/timeline_fuchsia.cc b/runtime/vm/timeline_fuchsia.cc
index 5d119fc8199..38bca2995a6 100644
--- a/runtime/vm/timeline_fuchsia.cc
+++ b/runtime/vm/timeline_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_FUCHSIA) && defined(SUPPORT_TIMELINE)
+#if defined(DART_HOST_OS_FUCHSIA) && defined(SUPPORT_TIMELINE)
 #include <lib/trace-engine/context.h>
 #include <lib/trace-engine/instrumentation.h>
 #include <zircon/syscalls.h>
@@ -121,4 +121,4 @@ void TimelineEventFuchsiaRecorder::OnEvent(TimelineEvent* event) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA) && defined(SUPPORT_TIMELINE)
+#endif  // defined(DART_HOST_OS_FUCHSIA) && defined(SUPPORT_TIMELINE)
diff --git a/runtime/vm/timeline_linux.cc b/runtime/vm/timeline_linux.cc
index 3756f1688ec..f685df22c9c 100644
--- a/runtime/vm/timeline_linux.cc
+++ b/runtime/vm/timeline_linux.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_LINUX) && defined(SUPPORT_TIMELINE)
+#if defined(DART_HOST_OS_LINUX) && defined(SUPPORT_TIMELINE)
 
 #include <errno.h>
 #include <fcntl.h>
@@ -115,4 +115,4 @@ void TimelineEventSystraceRecorder::OnEvent(TimelineEvent* event) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_LINUX) && !defined(PRODUCT)
+#endif  // defined(DART_HOST_OS_LINUX) && !defined(PRODUCT)
diff --git a/runtime/vm/timeline_macos.cc b/runtime/vm/timeline_macos.cc
index 93e0f7db202..1bda7e5c1b4 100644
--- a/runtime/vm/timeline_macos.cc
+++ b/runtime/vm/timeline_macos.cc
@@ -3,8 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_MACOS) && defined(SUPPORT_TIMELINE)
-
+#if defined(DART_HOST_OS_MACOS) && defined(SUPPORT_TIMELINE)
 
 #include "vm/log.h"
 #include "vm/timeline.h"
@@ -22,7 +21,7 @@ void TimelineEventMacosRecorder::OnEvent(TimelineEvent* event) {
     return;
   }
 
-#if defined(HOST_OS_SUPPORTS_SIGNPOST)
+#if defined(DART_HOST_OS_SUPPORTS_SIGNPOST)
   os_log_t log = event->stream_->macos_log();
   if (!os_signpost_enabled(log)) {
     return;
@@ -75,9 +74,9 @@ void TimelineEventMacosRecorder::OnEvent(TimelineEvent* event) {
     default:
       break;
   }
-#endif  // defined(HOST_OS_SUPPORTS_SIGNPOST)
+#endif  // defined(DART_HOST_OS_SUPPORTS_SIGNPOST)
 }
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_MACOS) && defined(SUPPORT_TIMELINE)
+#endif  // defined(DART_HOST_OS_MACOS) && defined(SUPPORT_TIMELINE)
diff --git a/runtime/vm/timeline_test.cc b/runtime/vm/timeline_test.cc
index f171921a555..97699cd3045 100644
--- a/runtime/vm/timeline_test.cc
+++ b/runtime/vm/timeline_test.cc
@@ -163,7 +163,7 @@ TEST_CASE(TimelineEventDurationPrintJSON) {
   event.DurationEnd();
 }
 
-#if defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX)
+#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
 TEST_CASE(TimelineEventPrintSystrace) {
   const intptr_t kBufferLength = 1024;
   char buffer[kBufferLength];
@@ -209,7 +209,7 @@ TEST_CASE(TimelineEventPrintSystrace) {
                                                kBufferLength);
   EXPECT_STREQ("", buffer);
 }
-#endif  // defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX)
+#endif  // defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX)
 
 TEST_CASE(TimelineEventArguments) {
   // Create a test stream.
diff --git a/runtime/vm/virtual_memory_compressed.h b/runtime/vm/virtual_memory_compressed.h
index 4201018ec96..0df8b1c0cab 100644
--- a/runtime/vm/virtual_memory_compressed.h
+++ b/runtime/vm/virtual_memory_compressed.h
@@ -20,9 +20,9 @@ static constexpr intptr_t kCompressedHeapNumPages =
 static constexpr intptr_t kCompressedHeapBitmapSize =
     kCompressedHeapNumPages / 8;
 
-#if !defined(HOST_OS_FUCHSIA)
+#if !defined(DART_HOST_OS_FUCHSIA)
 #define DART_COMPRESSED_HEAP
-#endif  // !defined(HOST_OS_FUCHSIA)
+#endif  // !defined(DART_HOST_OS_FUCHSIA)
 #endif  // defined(DART_COMPRESSED_POINTERS)
 
 #if defined(DART_COMPRESSED_HEAP)
diff --git a/runtime/vm/virtual_memory_fuchsia.cc b/runtime/vm/virtual_memory_fuchsia.cc
index 731b86d7f4a..7f7347d9877 100644
--- a/runtime/vm/virtual_memory_fuchsia.cc
+++ b/runtime/vm/virtual_memory_fuchsia.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_FUCHSIA)
+#if defined(DART_HOST_OS_FUCHSIA)
 
 #include "vm/virtual_memory.h"
 
@@ -279,4 +279,4 @@ void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_FUCHSIA)
+#endif  // defined(DART_HOST_OS_FUCHSIA)
diff --git a/runtime/vm/virtual_memory_posix.cc b/runtime/vm/virtual_memory_posix.cc
index aeb4a52a42c..2d8757daf98 100644
--- a/runtime/vm/virtual_memory_posix.cc
+++ b/runtime/vm/virtual_memory_posix.cc
@@ -3,7 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_ANDROID) || defined(HOST_OS_LINUX) || defined(HOST_OS_MACOS)
+#if defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX) ||            \
+    defined(DART_HOST_OS_MACOS)
 
 #include "vm/virtual_memory.h"
 
@@ -37,7 +38,7 @@ namespace dart {
 DECLARE_FLAG(bool, dual_map_code);
 DECLARE_FLAG(bool, write_protect_code);
 
-#if defined(TARGET_OS_LINUX)
+#if defined(DART_TARGET_OS_LINUX)
 DECLARE_FLAG(bool, generate_perf_events_symbols);
 DECLARE_FLAG(bool, generate_perf_jitdump);
 #endif
@@ -101,7 +102,7 @@ void VirtualMemory::Init() {
 
 #if defined(DUAL_MAPPING_SUPPORTED)
 // Perf is Linux-specific and the flags aren't defined in Product.
-#if defined(TARGET_OS_LINUX) && !defined(PRODUCT)
+#if defined(DART_TARGET_OS_LINUX) && !defined(PRODUCT)
   // Perf interacts strangely with memfds, leading it to sometimes collect
   // garbled return addresses.
   if (FLAG_generate_perf_events_symbols || FLAG_generate_perf_jitdump) {
@@ -136,7 +137,7 @@ void VirtualMemory::Init() {
   }
 #endif  // defined(DUAL_MAPPING_SUPPORTED)
 
-#if defined(HOST_OS_LINUX) || defined(HOST_OS_ANDROID)
+#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
   FILE* fp = fopen("/proc/sys/vm/max_map_count", "r");
   if (fp != nullptr) {
     size_t max_map_count = 0;
@@ -286,7 +287,7 @@ VirtualMemory* VirtualMemory::AllocateAligned(intptr_t size,
     // The mapping will be RX and stays that way until it will eventually be
     // unmapped.
     MemoryRegion region(region_ptr, size);
-    // DUAL_MAPPING_SUPPORTED is false in TARGET_OS_MACOS and hence support
+    // DUAL_MAPPING_SUPPORTED is false in DART_TARGET_OS_MACOS and hence support
     // for MAP_JIT is not required here.
     const int alias_prot = PROT_READ | PROT_EXEC;
     void* hint = reinterpret_cast<void*>(&Dart_Initialize);
@@ -333,11 +334,11 @@ VirtualMemory* VirtualMemory::AllocateAligned(intptr_t size,
 #endif
 
   int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
-#if (defined(HOST_OS_MACOS) && !defined(HOST_OS_IOS))
+#if (defined(DART_HOST_OS_MACOS) && !defined(DART_HOST_OS_IOS))
   if (is_executable && IsAtLeastOS10_14()) {
     map_flags |= MAP_JIT;
   }
-#endif  // defined(HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_MACOS)
 
   void* hint = nullptr;
   // Some 64-bit microarchitectures store only the low 32-bits of targets as
@@ -431,4 +432,5 @@ void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_ANDROID ... HOST_OS_LINUX ... HOST_OS_MACOS)
+#endif  // defined(DART_HOST_OS_ANDROID) || defined(DART_HOST_OS_LINUX) ||     \
+        // defined(DART_HOST_OS_MACOS)
diff --git a/runtime/vm/virtual_memory_win.cc b/runtime/vm/virtual_memory_win.cc
index 994833dbd40..5348b3cd735 100644
--- a/runtime/vm/virtual_memory_win.cc
+++ b/runtime/vm/virtual_memory_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
-#if defined(HOST_OS_WINDOWS)
+#if defined(DART_HOST_OS_WINDOWS)
 
 #include "vm/virtual_memory.h"
 
@@ -191,4 +191,4 @@ void VirtualMemory::Protect(void* address, intptr_t size, Protection mode) {
 
 }  // namespace dart
 
-#endif  // defined(HOST_OS_WINDOWS)
+#endif  // defined(DART_HOST_OS_WINDOWS)