From bbc8aedada6f9670c21fd142cf7771f55d6c5409 Mon Sep 17 00:00:00 2001
From: asiva <asiva@google.com>
Date: Sat, 20 Jun 2020 04:18:59 +0000
Subject: [PATCH] [VM/Runtime] - Fix for issue
 https://github.com/dart-lang/sdk/issues/42421

Set global null safety flag based on the snapshot instead of trying to
detect it per isolate (was causing issues with the vm isolate loading).
Should fix https://github.com/dart-lang/sdk/issues/42421

Bug:42421
Change-Id: I9143560b76fedcb991e96522cbf5d820fde99f7f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151866
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Siva Annamalai <asiva@google.com>
---
 runtime/vm/clustered_snapshot.cc | 15 +++++++++++++++
 runtime/vm/dart.cc               |  8 +++++---
 runtime/vm/dart_api_impl.cc      |  5 +++++
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/runtime/vm/clustered_snapshot.cc b/runtime/vm/clustered_snapshot.cc
index f3ca74d5071..4bd04c85ce3 100644
--- a/runtime/vm/clustered_snapshot.cc
+++ b/runtime/vm/clustered_snapshot.cc
@@ -6713,6 +6713,21 @@ char* SnapshotHeaderReader::InitializeGlobalVMFlagsFromSnapshot(
 #undef CHECK_FLAG
 #undef SET_FLAG
 
+#if defined(DART_PRECOMPILED_RUNTIME)
+    if (FLAG_null_safety == kNullSafetyOptionUnspecified) {
+      if (strncmp(cursor, "null-safety", end - cursor) == 0) {
+        FLAG_null_safety = kNullSafetyOptionStrong;
+        cursor = end;
+        continue;
+      }
+      if (strncmp(cursor, "no-null-safety", end - cursor) == 0) {
+        FLAG_null_safety = kNullSafetyOptionWeak;
+        cursor = end;
+        continue;
+      }
+    }
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
+
     cursor = end;
   }
 
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 3ec567d8947..31f297378ad 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -753,12 +753,13 @@ bool Dart::DetectNullSafety(const char* script_uri,
                             intptr_t kernel_buffer_size,
                             const char* package_config,
                             const char* original_working_directory) {
+#if !defined(DART_PRECOMPILED_RUNTIME)
   // Before creating the isolate we first determine the null safety mode
   // in which the isolate needs to run based on one of these factors :
   // - if loading from source, based on opt-in status of the source
   // - if loading from a kernel file, based on the mode used when
   //   generating the kernel file
-  // - if loading from an appJIT or AOT snapshot, based on the mode used
+  // - if loading from an appJIT, based on the mode used
   //   when generating the snapshot.
   ASSERT(FLAG_null_safety == kNullSafetyOptionUnspecified);
 
@@ -772,7 +773,6 @@ bool Dart::DetectNullSafety(const char* script_uri,
     }
   }
 
-#if !defined(DART_PRECOMPILED_RUNTIME)
   // If kernel_buffer is specified, it could be a self contained
   // kernel file or the kernel file of the application,
   // figure out the null safety mode by sniffing the kernel file.
@@ -791,8 +791,10 @@ bool Dart::DetectNullSafety(const char* script_uri,
     return KernelIsolate::DetectNullSafety(script_uri, package_config,
                                            original_working_directory);
   }
-#endif  // !defined(DART_PRECOMPILED_RUNTIME)
   return false;
+#else
+  UNREACHABLE();
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)
 }
 
 #if defined(DART_PRECOMPILED_RUNTIME)
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index b3800b5b45d..78930305403 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -6032,6 +6032,10 @@ DART_EXPORT bool Dart_DetectNullSafety(const char* script_uri,
                                        const uint8_t* snapshot_instructions,
                                        const uint8_t* kernel_buffer,
                                        intptr_t kernel_buffer_size) {
+#if defined(DART_PRECOMPILED_RUNTIME)
+  ASSERT(FLAG_null_safety != kNullSafetyOptionUnspecified);
+  return (FLAG_null_safety == kNullSafetyOptionStrong);
+#else
   bool null_safety;
   if (FLAG_null_safety == kNullSafetyOptionUnspecified) {
     null_safety = Dart::DetectNullSafety(
@@ -6041,6 +6045,7 @@ DART_EXPORT bool Dart_DetectNullSafety(const char* script_uri,
     null_safety = (FLAG_null_safety == kNullSafetyOptionStrong);
   }
   return null_safety;
+#endif  // defined(DART_PRECOMPILED_RUNTIME)
 }
 
 // --- Service support ---