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bazelbuild / bazel

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cxxopts and conlyopts parameters to cc_library #22041

Open davidben opened 1 month ago

davidben commented 1 month ago

Description of the feature request:

C and C++ compiler options are very related, but not always identical, ranging from variations in language specifiers and even warnings flags. For example GCC uses slightly different names for the same warning between C and C++: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmissing-prototypes https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmissing-declarations

Bazel does have --cxxopt and --conlyopt flags, but there is no way to do it from a build file. (A library project cannot control the flags used by upstreams.) It is possible to workaround this by splitting the target in two, but this is messy, particularly in a library project that already needs to support multiple build systems.

Other build tools already have this capability. https://discourse.cmake.org/t/language-specific-add-compile-options/2643 https://www.gnu.org/software/automake/manual/html_node/Standard-Configuration-Variables.html https://gn.googlesource.com/gn/+/main/docs/reference.md#var_cflags

Which category does this issue belong to?

C++ Rules

What underlying problem are you trying to solve with this feature?

See above

Which operating system are you running Bazel on?

All

What is the output of bazel info release?

No response

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

No response

comius commented 4 weeks ago

I'm leaning to P3, but I'd need more inputs of what can potentially be affected.

davidben commented 4 weeks ago

Do you mean that you need examples of projects that need it and use cases? Please see the bug report. BoringSSL has been having to work around this Bazel limitation for some time, as the build system simply does not meet our needs right now.

Indeed our testing fidelity is much worse than it could be because of Bazel here; as a library with some C++ internals but a C API, we would ideally have tests where our APIs' immediate callers are C. But this issue means that mixed C/C++ test binaries are so difficult to arrange that we largely don't bother. It also complicates incremental migration of the C portions of the library to C++.