Re: [PATCH] tests/tcg: Suppress compiler false-positive warning on sha1.c

[Brian Cain <brian.cain@oss.qualcomm.com>]

On 3/4/2025 6:51 AM, Peter Maydell wrote:
> On Tue, 4 Mar 2025 at 11:56, Alex Bennée <alex.bennee@linaro.org> wrote:
>> Peter Maydell <peter.maydell@linaro.org> writes:
>>> +# GCC versions 12/13/14/15 at least incorrectly complain about
>>> +# "'SHA1Transform' reading 64 bytes from a region of size 0"; see the gcc bug
>>> +# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106709
>>> +# Since this is just a standard piece of library code we've borrowed for a
>>> +# TCG test case, suppress the warning rather than trying to modify the
>>> +# code to work around the compiler.
>>> +sha1: CFLAGS+=-Wno-stringop-overread
>>> +
>> Sadly this breaks the hexagon compiler:
>>
>>    error: unknown warning option '-Wno-stringop-overread' [-Werror,-Wunknown-warning-option]
>>    Traceback (most recent call last):
>>      File "/home/alex/lsrc/qemu.git/tests/docker/docker.py", line 683, in <module>
>>        sys.exit(main())
>>                 ^^^^^^
>>      File "/home/alex/lsrc/qemu.git/tests/docker/docker.py", line 679, in main
>>        return args.cmdobj.run(args, argv)
>>               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>      File "/home/alex/lsrc/qemu.git/tests/docker/docker.py", line 657, in run
>>        return Docker().run(cmd, False, quiet=args.quiet,
>>               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>      File "/home/alex/lsrc/qemu.git/tests/docker/docker.py", line 370, in run
>>        ret = self._do_check(["run", "--rm", "--label",
>>              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>      File "/home/alex/lsrc/qemu.git/tests/docker/docker.py", line 247, in _do_check
>>        return subprocess.check_call(self._command + cmd, **kwargs)
>>               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>      File "/usr/lib/python3.11/subprocess.py", line 413, in check_call
>>        raise CalledProcessError(retcode, cmd)
>>    subprocess.CalledProcessError: Command '['podman', 'run', '--rm', '--label', 'com.qemu.instance.uuid=5bbb7b6ed2ea4377b9b6d646859ec4ea', '--userns=keep-id', '-u', '1000', '-w', '/home/alex/lsrc/qemu.git/builds/all/tests/tcg/hexagon-linux-user', '-v', '/home/alex/lsrc/qemu.git/builds/all/tests/tcg/hexagon-linux-user:/home/alex/lsrc/qemu.git/builds/all/tests/tcg/hexagon-linux-user:rw', '-v', '/home/alex/lsrc/qemu.git:/home/alex/lsrc/qemu.git:ro,z', 'qemu/debian-hexagon-cross', 'hexagon-unknown-linux-musl-clang', '-Wno-incompatible-pointer-types', '-Wno-undefined-internal', '-fno-unroll-loops', '-fno-stack-protector', '-Wall', '-Werror', '-O0', '-g', '-fno-strict-aliasing', '-Wno-stringop-overread', '-mv73', '-O2', '-static', '/home/alex/lsrc/qemu.git/tests/tcg/multiarch/sha1.c', '-o', 'sha1', '-static']' returned non-zero exit status 1.
>>    filter=--filter=label=com.qemu.instance.uuid=5bbb7b6ed2ea4377b9b6d646859ec4ea
>>    make[1]: *** [Makefile:122: sha1] Error 1
>>    make: *** [/home/alex/lsrc/qemu.git/tests/Makefile.include:52: build-tcg-tests-hexagon-linux-user] Error 2
>>
>> Is it that new an option?
> I think it's new-ish (gcc 11?). On the other hand


I was going to volunteer to update the toolchain used for hexagon to 
address this.  But unfortunately this warning is still not supported in 
clang 21.

https://github.com/llvm/llvm-project/issues/72455 sounds like it's not 
very likely to arrive any time soon.


So "-Wno-unknown-warning-option" does indeed seem like a good workaround.


> -Wno-unknown-warning-option is quite old, and would suppress
> this error. If we do
>   CFLAGS+=-Wno-unknown-warning-option -Wno-stringop-overread
>
> does that work?
>
> (Meson has cc.get_supported_arguments() that we can use to
> filter out -Wfoo/-Wno-foo options that the compiler doesn't
> support, but since this is built via a makefile rather than
> by meson that's not conveniently accessible.)
>
> -- PMM