Do not retain a name string for generated module maps

Copybara Import from https://github.com/bazelbuild/rules_cc/pull/789

BEGIN_PUBLIC
Do not retain a name string for generated module maps (#789)

Module maps generated for a target are named after the target's label. Since the generated module map file is declared by that very target, the name can be derived on demand from the file's owner label, which the `File` object already retains. The `name` field of the module map struct becomes optional, with `None` meaning "named after the label of the target that generated the module map file", and two central helpers (`get_module_map_name`, `get_module_map_label`) derive the string form and the `Label` form where needed.

This fixes the round-trip bug originally addressed in https://github.com/bazelbuild/rules_cc/pull/633, but avoids the memory regression that caused it to be rolled back in b81b6e4 (because retaining `Label` objects increased memory usage overall). Deriving the name on demand retains nothing extra as the owner label is already retained by the `File` and all name materializations are transient only (such as in `map_each` callbacks).

Names are now the unambiguous canonical label string, except that main repository labels drop the leading `@@` (`//pkg:lib`), keeping the traditional module name format. Special module maps (the crosstool module map, ObjC internal module maps) keep their explicitly provided names.

Closes #789
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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
COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_cc/pull/789 from fmeum:module-map-label 68848659e21ef3b4d223a92dc19b4711b604b82e
PiperOrigin-RevId: 964972527
Change-Id: If97a7c4491d670e825b621e80541a064ffe8769f
5 files changed
tree: 12a9ec3bda4002b2a8f0331c7f141e89b562ee20
  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: