We use clang-tidy to lint C++ code and aim to keep the repository warning-clean.
The linter is configured in the root level
.clang-tidy file. Developers
should not create additional configuration files at a lower level, as
this will cause disagreements in the tree.
How to lint
fx lint is a Fuchsia script that wraps language-specific linters in a common
command line interface. It gathers a list of files, based on the options you
specify, separates them by matching linter, and executes each required linter.
clang-tidy is used for C and C++ files.
Without any other arguments,
fx lint lints the files in your
most recent git commit, and passes them through the linter:
To restrict linting to C++, add a double-dash (--) followed by the file pattern(s) to match, such as:
fx lint -- '*.cc' '*.cpp'
To run a specific GN target through the linter, use:
fx lint --target=<target>
In order to lint all files under the current working directory, add
fx lint --all from the top-level
fuchsia directory is generally not
recommended, and will likely take several hours to complete. Be certain you
cd to the best top level directory for your analysis requirements. For example:
(cd <your/subdir>; fx lint --all -- '*.cc')
You can also add
--fix in order to automatically generate fixes for some (but
not all) of the warnings.
Additional options and examples are documented in the tool itself. For the most up
to date documentation on
fx lint, including examples, run:
fx lint --help
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
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:
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
misc-non-private-member-variables-in-classes- We don't allow classes/structs with a mix of private and public members, but all public is fine.
modernize-deprecated-headers- Fuchsia uses old-style C headers
modernize-use-nodiscard- Not generally used in the Fuchsia codebase
modernize-raw-string-literal- the check was suggesting to convert
\xFFliterals, 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-emplace- enabled the IgnoreImplicitConstructors option to comply with Abseil Tip of the Week #112.
modernize-use-equals-delete- flagging all gtest TEST_F
modernize-use-trailing-return-type- Fuchsia C++ code typically uses the
int foo()style of defining functions, and not the
auto foo() -> intstyle as recommended by this check.
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.
Strictly speaking it is not linting, but the Clang static analyzer can do deep analysis to find bugs. See Static analysis for details.