On Sat, Jun 12, 2021, 1:56 AM Nathan Chancellor <nathan@kernel.org> wrote:

> On 6/11/2021 1:58 AM, Hyeonggon Yoo wrote:> After playing with clang
> more a bit, I got to know that
> > compiletime_assert makes weird link error (undefined reference to
> > compiletime_assert_XXX), Not a compile error.
> >
> >
> > I think it's time to CC ClangBuiltLinux maintainers, who work on
> > clang/llvm build support.
> >
> > [+CC Nathan and Nick]
> >
> > I assumeed that compiletime_assert (in linux/compiler.h) will make
> > compiler error, but it makes no compile error, just makes weird link
> error.
> >
> > I'm not sure it it works well with clang, or somewhat buggy status?
>
> I am guessing this alone is why we were keyed into the thread so I am
> just going to respond to this.
>

Thank you for quick reply!

Unfortunately, this is a known issue with clang:
>
> https://github.com/ClangBuiltLinux/linux/issues/1173
>
> https://bugs.llvm.org/show_bug.cgi?id=16428



> As you noticed, building the full kernel will result in a link error but
> it would certainly be nicer if it were a compiler error. Something for
> us to improve indeed but I am not sure when we will be able to allocate
> resources for that.


I wanted to be sure if we can use compiletime_assert for clang. Then there
is room for improvement, but it seems okay.

Until then, you can build a full kernel to get the
> failing translation unit then use nm or readelf when building the single
> translation unit to see if there are any "__compiletime_assert" symbols.
>

Okay, then we should find symbol like that until improved.

It may confuse developer, but it seems okay for our code to support clang
as it meets minimal condition - build failure.

And I hope it become improved in future!

Thanks,
Hyeonggon

Cheers,
> Nathan
>