Bazel should pass -no_warning_for_no_symbols to libtool when using XCode toolchain

[nelhage-stripe]

Description of the problem / feature request:

I have a (proprietary) project that contains some C++ source code files which, on certain platforms, emit no symbols due to #ifdefs. When I build on macOS, bazel build prints useless warnings like:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: bazel-out/darwin-fastbuild/bin/libempty.a(empty.o) has no symbols                                     

Feature requests: what underlying problem are you trying to solve with this feature?

I'd like bazel to pass flags to suppress this useless warning.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

You can easily reproduce with a cc_library rule with empty .c file; I've uploaded a minimal test case here: https://gist.github.com/nelhage-stripe/df1374361be6daa938e6ec75f93daf7a

What operating system are you running Bazel on?

macOS

What's the output of bazel info release?

release 0.16.1

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

I believe passing no_warning_for_no_symbols to libtool (which is $AR on the xcode toolchain, as I understand it) will suppress this warning.

[tetromino]

Makes sense, we should fix this.

[tetromino]

This involves updating the script that generates bazel/tools/osx/crosstool/CROSSTOOL.tpl - I've filed an internal bug for it.

[tetromino]

For future reference - internal bug is b/113576433

[jamiesnape]

Any progress on this? Since #6478 merged, this is the one remaining source of needless spam in the output on Mac.

[tetromino]

Sorry, this fell through the cracks. I will try to fix.

[tetromino]

Fixed by 81b59f0.

[cpsauer]

Looks like some of these are still sneaking through. Posted more in the (still open) #4057 (comment)

[keith]

can you file a new issue with a repro? should be an easy fix

[cpsauer]

On it! Thanks, Keith. Amazed at your breadth

[cpsauer]

(You're sure you don't want it in the other issue, still open and applicable?)

[keith]

either way

[phst]

I think this issue has reappeared now that C++ builds on macOS use the Unix toolchain by default (Bazel 7). I guess Bazel should pass the necessary flags for the Unix toolchain as well, at least if the macOS binaries (and not GNU ones installed via e.g. Homebrew) are used for compiling.