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bazel/rules_cc/bcd0612c5890fd948d278090c164d211617b6c3f
commit
bcd0612c5890fd948d278090c164d211617b6c3f
[log]
author
Googler <noreply@google.com>
Thu Jul 23 17:26:24 2026 -0700
committer
Copybara-Service <copybara-worker@google.com>
Thu Jul 23 17:26:49 2026 -0700
tree
50d08f79302c3b3ff9b59f988e01edb8c8b9dea4
parent
aedc636a1ed20dea04fbb25b84833ba717db5df7 [diff]
[bzl-optimizer] Eliminate redundant Starlark list allocations in C++ build variables.

Optimize Starlark memory usage during C++ build variable evaluation by replacing empty mutable lists with empty tuples `()`:
1. `link_build_variables.bzl`: Replaces empty `user_link_flags` with `()` via `user_link_flags if (is_using_linker and user_link_flags) else ()`. Guards dynamic library flag processing with `and user_link_flags` to skip `_remove_pie` when empty, and updates `_remove_pie` to return a tuple.
2. `compile_build_variables.bzl`: Replaces `[]` with `()` for `MODULE_FILES` when `use_header_modules` feature is enabled.

Memory Evidence (statistics from the analysis phase of a mars-lro build):
- Confirmed zero allocations remaining at line 261 of `link_build_variables.bzl` in post-optimization benchmark run.
- Eliminates 135,226 empty list allocations from `link_build_variables.bzl`.
- Eliminates 89,276 empty list allocations from `compile_build_variables.bzl`.
- Net live Starlark list instance reduction: 224,502 instances.

Startblock:
  * // Put other blockers before this line to avoid churning.
  * has lgtm
  * is approved
  * and then
  * all comments are resolved
  * and then
  *[] allows unknown commit
PiperOrigin-RevId: 953043322
Change-Id: I6801c009e719939af7eb4f0c73ec2e22d9e44275
2 files changed
tree: 50d08f79302c3b3ff9b59f988e01edb8c8b9dea4
  1. .bazelci/
  2. .bcr/
  3. .github/
  4. cc/
  5. docs/
  6. examples/
  7. tests/
  8. .bazelignore
  9. .bazelrc
  10. .gitignore
  11. AUTHORS
  12. BUILD
  13. CODEOWNERS
  14. CONTRIBUTING.md
  15. googletest.patch
  16. ISSUE_TEMPLATE.md
  17. LICENSE
  18. local_bazel.bzl
  19. MODULE.bazel
  20. README.md
  21. WORKSPACE
  22. WORKSPACE.bzlmod
README.md

C++ rules for Bazel

  • Postsubmit Build status

This repository contains C, C++, and Objective-C language support for the Bazel build system.

For this module's main reference, see the Bazel documentation.

Get Started

Install Bazel

Follow the official instructions to Install Bazel.

Add rules_cc to your MODULE.bazel

Add the latest release to your MODULE.bazel project file.

Declare a build target

In a BUILD.bazel file, import and use the rules:

load("@rules_cc//cc:cc_binary.bzl", "cc_binary")

cc_binary(
    name = "hello_world",
    srcs = ["hello_world.cc"],
)

Build and run your project

Build and run your C/C++ binary with one command:

$ bazel run hello_world

To build the project without running the binary, use Bazel's build subcommand:

$ bazel build hello_world

Toolchains

Default autoconfigured toolchain

rules_cc includes an auto-configured toolchain that uses the local compiler installed on the host machine.

You can disable the autoconfigured C/C++ toolchain by adding the following Bazel flag to your project's .bazelrc file:

--repo_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1

Hermetic toolchains

Configuring a hermetic toolchain makes your build more deterministic. rules_cc itself does not yet offer a hermetic toolchain distribution. Other community owned and maintained projects offer hermetic C/C++ toolchains:

Contributing

Bazel and rules_cc are the work of many contributors. We appreciate your help!

To contribute, please read the contribution guidelines: CONTRIBUTING.md.

Note that the rules_cc use the GitHub issue tracker for bug reports and feature requests only. For asking questions see: