Re: [linux-next:master 7012/7430] include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_183' declared with attribute error: unexpected size in kmalloc_index()

From: Nathan Chancellor <nathan@kernel.org>
To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Vlastimil Babka <vbabka@suse.cz>
Cc: kernel test robot <lkp@intel.com>,
	kbuild-all@lists.01.org,
	Linux Memory Management List <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com
Subject: Re: [linux-next:master 7012/7430] include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_183' declared with attribute error: unexpected size in kmalloc_index()
Date: Fri, 11 Jun 2021 09:56:30 -0700	[thread overview]
Message-ID: <99de1f59-1e38-6410-86ff-0ea1f016c49f@kernel.org> (raw)
In-Reply-To: <CAB=+i9StdrGQWXXoQHKU5oLK3eKuNcuCAbrd88kPLzM_Yw==Jg@mail.gmail.com>

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.

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. 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.

Cheers,
Nathan