Allow the VM to read Kernel files with external libraries

The meaning of a Kernel file with an external library is that the
library is one that is already known to be loaded in the VM.

Fixes issue #30111.

BUG=https://github.com/dart-lang/sdk/issues/30111
R=jensj@google.com

Review-Url: https://codereview.chromium.org/2995423002 .

runtime/vm/kernel_binary.h

@@ -206,7 +206,7 @@ class Reader {
 
   bool ReadBool() { return (ReadByte() & 1) == 1; }
 
-  word ReadFlags() { return ReadByte(); }
+  uint8_t ReadFlags() { return ReadByte(); }
 
   Tag ReadTag(uint8_t* payload = NULL) {
     uint8_t byte = ReadByte();

runtime/vm/kernel_binary_flowgraph.cc

@@ -87,7 +87,7 @@ void VariableDeclarationHelper::ReadUntilExcluding(Field field) {
       equals_position_ = builder_->ReadPosition();  // read equals position.
       if (++next_read_ == field) return;
     case kFlags:
-      flags_ = builder_->ReadFlags();  // read flags.
+      flags_ = builder_->ReadFlags();
       if (++next_read_ == field) return;
     case kNameIndex:
       name_index_ = builder_->ReadStringReference();  // read name index.
@@ -133,7 +133,7 @@ void FieldHelper::ReadUntilExcluding(Field field,
       end_position_ = builder_->ReadPosition(false);  // read end position.
       if (++next_read_ == field) return;
     case kFlags:
-      flags_ = builder_->ReadFlags();  // read flags.
+      flags_ = builder_->ReadFlags();
       if (++next_read_ == field) return;
     case kName:
       builder_->SkipName();  // read name.
@@ -205,7 +205,7 @@ void ProcedureHelper::ReadUntilExcluding(Field field) {
       kind_ = static_cast<Kind>(builder_->ReadByte());
       if (++next_read_ == field) return;
     case kFlags:
-      flags_ = builder_->ReadFlags();  // read flags.
+      flags_ = builder_->ReadFlags();
       if (++next_read_ == field) return;
     case kName:
       builder_->SkipName();  // read name.
@@ -256,7 +256,7 @@ void ConstructorHelper::ReadUntilExcluding(Field field) {
       end_position_ = builder_->ReadPosition();  // read end position.
       if (++next_read_ == field) return;
     case kFlags:
-      flags_ = builder_->ReadFlags();  // read flags.
+      flags_ = builder_->ReadFlags();
       if (++next_read_ == field) return;
     case kName:
       builder_->SkipName();  // read name.
@@ -410,8 +410,7 @@ void LibraryHelper::ReadUntilExcluding(Field field) {
   // Ordered with fall-through.
   switch (next_read_) {
     case kFlags: {
-      word flags = builder_->ReadFlags();  // read flags.
-      ASSERT(flags == 0);                  // external libraries not supported
+      flags_ = builder_->ReadFlags();
       if (++next_read_ == field) return;
     }
     case kCanonicalName:
@@ -4660,11 +4659,11 @@ void StreamingFlowGraphBuilder::SkipLibraryCombinator() {
 }
 
 void StreamingFlowGraphBuilder::SkipLibraryDependency() {
-  ReadFlags();                                   // read flags.
-  SkipListOfExpressions();                       // Read annotations.
-  ReadCanonicalNameReference();                  // read target_reference.
-  ReadStringReference();                         // read name_index.
-  intptr_t combinator_count = ReadListLength();  // read list length.
+  ReadFlags();
+  SkipListOfExpressions();  // Annotations.
+  ReadCanonicalNameReference();
+  ReadStringReference();  // Name.
+  intptr_t combinator_count = ReadListLength();
   for (intptr_t i = 0; i < combinator_count; ++i) {
     SkipLibraryCombinator();
   }
@@ -4714,10 +4713,6 @@ Tag StreamingFlowGraphBuilder::PeekTag(uint8_t* payload) {
   return reader_->PeekTag(payload);
 }
 
-word StreamingFlowGraphBuilder::ReadFlags() {
-  return reader_->ReadFlags();
-}
-
 void StreamingFlowGraphBuilder::loop_depth_inc() {
   ++flow_graph_builder_->loop_depth_;
 }

runtime/vm/kernel_binary_flowgraph.h

@@ -119,7 +119,7 @@ class VariableDeclarationHelper {
 
   TokenPosition position_;
   TokenPosition equals_position_;
-  word flags_;
+  uint8_t flags_;
   StringIndex name_index_;
 
  private:
@@ -190,7 +190,7 @@ class FieldHelper {
   NameIndex canonical_name_;
   TokenPosition position_;
   TokenPosition end_position_;
-  word flags_;
+  uint8_t flags_;
   intptr_t source_uri_index_;
   intptr_t annotation_count_;
 
@@ -265,7 +265,7 @@ class ProcedureHelper {
   TokenPosition position_;
   TokenPosition end_position_;
   Kind kind_;
-  word flags_;
+  uint8_t flags_;
   intptr_t source_uri_index_;
   intptr_t annotation_count_;
 
@@ -322,7 +322,7 @@ class ConstructorHelper {
   NameIndex canonical_name_;
   TokenPosition position_;
   TokenPosition end_position_;
-  word flags_;
+  uint8_t flags_;
   intptr_t annotation_count_;
 
  private:
@@ -410,6 +410,10 @@ class LibraryHelper {
     kEnd,
   };
 
+  enum Flag {
+    kExternal = 1,
+  };
+
   explicit LibraryHelper(StreamingFlowGraphBuilder* builder) {
     builder_ = builder;
     next_read_ = kFlags;
@@ -424,6 +428,9 @@ class LibraryHelper {
   void SetNext(Field field) { next_read_ = field; }
   void SetJustRead(Field field) { next_read_ = field + 1; }
 
+  bool IsExternal() const { return (flags_ & kExternal) != 0; }
+
+  uint8_t flags_;
   NameIndex canonical_name_;
   StringIndex name_index_;
   intptr_t source_uri_index_;
@@ -837,7 +844,7 @@ class StreamingFlowGraphBuilder {
   void record_yield_position(TokenPosition position);
   Tag ReadTag(uint8_t* payload = NULL);
   Tag PeekTag(uint8_t* payload = NULL);
-  word ReadFlags();
+  uint8_t ReadFlags() { return reader_->ReadFlags(); }
 
   void loop_depth_inc();
   void loop_depth_dec();

runtime/vm/kernel_reader.cc

@@ -253,6 +253,8 @@ void KernelReader::ReadLibrary(intptr_t kernel_offset) {
   LibraryHelper library_helper(&builder_);
   library_helper.ReadUntilIncluding(LibraryHelper::kCanonicalName);
   Library& library = LookupLibrary(library_helper.canonical_name_);
+  // The Kernel library is external implies that it is already loaded.
+  ASSERT(!library_helper.IsExternal() || library.Loaded());
   if (library.Loaded()) return;
 
   library_helper.ReadUntilIncluding(LibraryHelper::kName);

runtime/vm/kernel_reader.h

@@ -94,7 +94,7 @@ class KernelReader {
     reader.set_offset(reader.ReadUInt32());
 
     // Start reading library.
-    reader.ReadFlags();  // read flags.
+    reader.ReadFlags();
     return reader.ReadCanonicalNameReference();
   }
 

tools/patch_sdk.dart

@@ -164,16 +164,10 @@ Future _main(List<String> argv) async {
         Uri.parse('dart:$vmserviceName'),
         new CompilerOptions()
           ..setExitCodeOnProblem = true
-          // TODO(sigmund): investigate. This should be outline, but it breaks
-          // vm-debug tests. Issue #30111
-          ..sdkSummary = platform
+          ..sdkSummary = outline
           ..librariesSpecificationUri = vmserviceJsonUri
           ..packagesFileUri = packages);
     Uri vmserviceUri = outDirUri.resolve('$vmserviceName.dill');
-    // TODO(sigmund): remove. This is a workaround because in the VM
-    // doesn't support loading vmservice if it contains external libraries
-    // (there is an assertion that only fails in debug builds). Issue #30111
-    program.libraries.forEach((l) => l.isExternal = false);
     await writeProgramToFile(program, vmserviceUri);
   }