We use clang-tidy to lint C++ code and aim to keep the repository warning-clean. The linter is configured in the .clang-tidy file.

How to lint

In order to run a specific GN target through the linter, run:

fx clang-tidy --target=<target>

You can also add --fix in order to automatically generate fixes for some (but not all) of the warnings.

Alternatively, you can run the following to run the current patch through the linter:

../scripts/git-file-tidy [--out-dir out/debug-x64]

In order to run the entire repository through the linter, add --all. You can also add --fix in order to automatically generate fixes for some (but not all) of the warnings.

Suppressing warnings

Any warning can be suppressed by adding a // NOLINT(<check_name>) or a // NOLINTNEXTLINE(<check_name>) comment to the offending line. It is also possible to disable the check entirely within the repository by editing the .clang-tidy file.


There are a number of check categories enabled, and specific checks within them have been disabled for the reasons below. The list of enabled check categories is as follows:

  • bugprone-*
  • clang-diagnostic-*
  • google-*
  • misc-*
  • modernize-
  • performance-*
  • readability-*

This list tracks the reasons for which we disabled in particular checks:

  • clang-diagnostic-unused-command-line-argument - ninja-generated compilation database contains the linker argument which ends up unused and triggers this warning for every file
  • misc-noexcept* - Fuchsia doesn't use C++ exceptions
  • modernize-deprecated-headers - Fuchsia uses old-style C headers
  • modernize-raw-string-literal - the check was suggesting to convert \xFF literals, which we'd rather keep in the escaped form.
  • modernize-return-braced-init-list - concerns about readability of returning braced initialization list for constructor arguments, prefer to use a constructor explicitly
  • modernize-use-equals-delete - flagging all gtest TEST_F
  • modernize-use-equals-default - Fuchsia chose not to impose a preference for “= default”
  • performance-unnecessary-value-param - it was flagging view classes which we prefer to pass by value
  • readability-implicit-bool-conversion - Fuchsia C++ code commonly uses implicit bool cast of pointers and numbers
  • readability-isolate-declaration - Zircon code commonly uses paired declarations.
  • readability-uppercase-literal-suffix - Fuchsia C++ code chooses not to impose a style on this.