Re: [Bug Report] selftests: Clang: kselftests build errors in KernelCI

[Shuah Khan]

On 4/4/24 10:34, Nick Desaulniers wrote:
> Thanks for the report.  We've been tracking getting this working for a
> while: https://github.com/ClangBuiltLinux/linux/issues/1698.  Other
> fires have continued to take priority.
>
> On Thu, Apr 4, 2024 at 9:30 AM Muhammad Usama Anjum
> <usama.anjum@xxxxxxxxxxxxx> wrote:
> > Hi,
> >
> > We have caught bugs in kselftest suites on linux-next and on stable-RCs etc
> > when using clang. There are two types of bugs (logs with clang-17 are
> > attached.):
> > As usually people use GCC, there are GCC-specific flags added to the
> > Makefiles that clang doesn't recognize. For example:
> > * clang: error: argument unused during compilation: '-pie'
> > [-Werror,-Wunused-command-line-argument]
> > * clang: error: unknown argument '-static-libasan'; did you mean
> > '-static-libsan'?
> > * clang: error: cannot specify -o when generating multiple output files
> >
> > Clang has best static analysis tools. It is reporting static errors. For
> > example:
> > * test_execve.c:121:13: warning: variable 'have_outer_privilege' is used
> > uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> > * test_execve.c:121:9: note: remove the 'if' if its condition is always true
> > * test_memcontrol.c:727:6: warning: variable 'fd' is used uninitialized
> > whenever 'if' condition is true [-Wsometimes-uninitialized]
> >
> > We have found these issues through our new KernelCI system when enabling
> > kselftest and clang there. The new system dashboard is a WIP, so It is not
> > the web dashboard you are used-to with in KernelCI. We can show you ways of
> > pulling the data if you are interest into.
> >
> > Unless the above is some sort of false-positive or misconfiguration, it
> > would be great to support clang for kselftests. What we can do from our
> > side is that clang kselftests builds should be enabled on KernelCI to find
> > and fix the errors. What is your stance about this?
>
> As with anything kernel related; help send patches for obvious fixes.
> Or provide steps to reproduce in
> https://github.com/ClangBuiltLinux/linux/issues/1698.

+1 on this. Please send patches to fixes as you find them. We have
been taking fixes found by clang and -Wformat-security, -Werror
checks.

thanks,
-- Shuah