[vm] Reorder ELF sections more sensibly.

Previous CLs made it so that we don't need to calculate memory offsets
until finalization. This means that we can now reorder sections as
desired and then calculate the memory offsets at the same time as the
file offsets.

Thus, we reorder them so that writable, non-executable allocated
sections come first (due to requirements by some loaders to not sandwich
writable segments between non-writable ones), followed by non-writable,
non-executable allocated sections, followed by non-writable, executable
sections, and finally unallocated sections (to avoid differences in
memory offsets between snapshots and separate debugging information).
This ordering minimizes the number of segments that need to be created
(5 or 6, depending on whether a build ID exists).

Since we can reorder, we also delay the creation of the build ID (if
generated) and BSS sections until finalization, instead of creating them
up front in the constructor.

TEST=Further refactorings, so existing tests.

Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-debug-simarm_x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-release-simarm-try,vm-kernel-precomp-linux-release-simarm64-try,vm-kernel-precomp-dwarf-linux-product-x64-try
Change-Id: Id4142a021c2bb800938e8bc711b1b8a7529bff51
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/205780
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
3 files changed
tree: d3c305b01e6343dc0f181eaff47af1f1bb360cfb
  1. .dart_tool/
  2. .github/
  3. benchmarks/
  4. build/
  5. client/
  6. docs/
  7. pkg/
  8. runtime/
  9. samples/
  10. samples-dev/
  11. samples_2/
  12. sdk/
  13. tests/
  14. third_party/
  15. tools/
  16. utils/
  17. .clang-format
  18. .gitattributes
  19. .gitconfig
  20. .gitignore
  21. .gn
  22. .mailmap
  23. .packages
  24. .style.yapf
  25. .vpython
  26. AUTHORS
  27. BUILD.gn
  28. CHANGELOG.md
  29. codereview.settings
  30. CONTRIBUTING.md
  31. DEPS
  32. LICENSE
  33. PATENT_GRANT
  34. PRESUBMIT.py
  35. README.dart-sdk
  36. README.md
  37. sdk_args.gni
  38. WATCHLISTS
README.md

Dart

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's 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.

See LICENSE and PATENT_GRANT.

Using Dart

Visit dart.dev to learn more about the language, tools, and to find codelabs.

Browse pub.dev for more packages and libraries contributed by the community and the Dart team.

Our API reference documentation is published at api.dart.dev, based on the stable release. (We also publish docs from our beta and dev channels, as well as from the primary development branch).

Building Dart

If you want to build Dart yourself, here is a guide to getting the source, preparing your machine to build the SDK, and building.

There are more documents on our wiki.

Contributing to Dart

The easiest way to contribute to Dart is to file issues.

You can also contribute patches, as described in Contributing.