Re: [PATCH v4 1/3] compiler-gcc.h: add gnu_inline to all inline declarations

From: Sedat Dilek
Date: Fri Jun 08 2018 - 06:04:49 EST

On Fri, Jun 8, 2018 at 9:59 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Thu, Jun 7, 2018 at 10:49 PM, Nick Desaulniers
> <ndesaulniers@xxxxxxxxxx> wrote:
>> Functions marked extern inline do not emit an externally visible
>> function when the gnu89 C standard is used. Some KBUILD Makefiles
>> overwrite KBUILD_CFLAGS. This is an issue for GCC 5.1+ users as without
>> an explicit C standard specified, the default is gnu11. Since c99, the
>> semantics of extern inline have changed such that an externally visible
>> function is always emitted. This can lead to multiple definition errors
>> of extern inline functions at link time of compilation units whose build
>> files have removed an explicit C standard compiler flag for users of GCC
>> 5.1+ or Clang.
>> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
>> Suggested-by: H. Peter Anvin <hpa@xxxxxxxxx>
>> Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
> I suspect this will break Geert's gcc-4.1.2, which I think doesn't have that
> attribute yet (4.1.3 or higher have it according to the documentation.
> It wouldn't be hard to work around that if we want to keep that version
> working, or we could decide that it's time to officially stop supporting
> that version, but we should probably decide on one or the other.

Good point.
What is the minimum requirement of GCC version currently?
AFAICS x86/asm-goto support requires GCC >= 4.5?

Just FYI...
...saw the last days in upstream commits that kbuild/kconfig for
4.18-rc1 offers possibilities to check for cc-version dependencies.

- sed@ -