[vm/kernel] Use GC-tracked ExternalTypedData/TypedDataView for kernel buffers

Until now we often leaked kernel buffers (e.g. hot reload buffers) because various
objects were referencing ExternalTypedData objects pointing into the middle of
c-allocated memory. This made it impossible for the GC to determine when the last
reference is gone.

This CL ensures that the actual buffers are *always* made available via
ExternalTypedData and any inner pointers into it are created via TypedDataViews.

The embedder guarantees to the free kernel buffers it has provided to:
    - Dart_CreateIsolateFromKernel
    - Dart_LoadScriptFromKernel
    - Dart_LoadLibraryFromKernel
    - Dart_SetDartLibrarySourcesKernel
on isolate shutdown.

All other kernel buffers will get a finalizer attached, which ensures the
kernel buffers get freed by the GC once they are no longer referenced:
    - Kernel blobs for expression evaluation
    - Kernel blobs for Hot-Reload
    - Kernel blobs for cc tests

Fixes https://github.com/dart-lang/sdk/issues/33973
Fixes https://github.com/dart-lang/sdk/issues/36857
Issue https://github.com/dart-lang/sdk/issues/37030

Change-Id: I1cc410c94c0f4b229413e793728a261afcb10aaf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/103130
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
35 files changed
tree: 9c4d342a3aa847830c9b676307602ac3e2c49338
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  14. DEPS
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  18. README.dart-sdk
  19. README.md
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  22. client/
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A client-optimized language for fast apps on any platform

Dart is:

  • Optimized for UI: Develop with a programming language specialized around the needs of user interface creation

  • Productive: Make changes iteratively: use hot reload to see the result instantly in your running app

  • Fast on all platforms: Compile to ARM & x64 machine code for mobile, desktop, and backend. Or compile to JavaScript for the web

Dart has flexible compiler technology lets you run Dart code in different ways, depending on your target platform and goals:

  • Dart Native: For programs targeting devices (mobile, desktop, server, and more), Dart Native includes both a Dart VM with JIT (just-in-time) compilation and an AOT (ahead-of-time) compiler for producing machine code.

  • Dart Web: For programs targeting the web, Dart Web includes both a development time compiler (dartdevc) and a production time compiler (dart2js).

Dart platforms illustration

License & patents

Dart is free and open source.


Using Dart

Visit the dart.dev to learn more about the language, tools, getting started, and more.

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There are more documents on our wiki.

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You can also contribute patches, as described in Contributing.