On Thu, Jun 7, 2018 at 10:26 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > On Tue, Jun 5, 2018 at 10:23 AM Joe Perches <joe@xxxxxxxxxxx> wrote: > > > > On Tue, 2018-06-05 at 10:05 -0700, Nick Desaulniers 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. > > [] > > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > > [] > > > @@ -72,17 +72,24 @@ > > > * -Wunused-function. This turns out to avoid the need for complex #ifdef > > > * directives. Suppress the warning in clang as well by using "unused" > > > * function attribute, which is redundant but not harmful for gcc. > > > + * Prefer gnu_inline, so that extern inline functions do not emit an > > > + * externally visible function. This makes extern inline behave as per gnu89 > > > + * semantics rather than c99. This prevents multiple symbol definition errors > > > + * of extern inline functions at link time. > > > */ > > > #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ > > > !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) > > > -#define inline inline __attribute__((always_inline,unused)) notrace > > > -#define __inline__ __inline__ __attribute__((always_inline,unused)) notrace > > > -#define __inline __inline __attribute__((always_inline,unused)) notrace > > > +#define inline \ > > > + inline __attribute__((always_inline, unused, gnu_inline)) notrace > > > +#define __inline__ \ > > > + __inline__ __attribute__((always_inline, unused, gnu_inline)) notrace > > > +#define __inline \ > > > + __inline __attribute__((always_inline, unused, gnu_inline)) notrace > > > > Perhaps these are simpler as > > > > #define __inline__ inline > > #define __inline inline > > Probably want: > > #define __inline__ __inline__ inline > #define __inline __inline inline Oh, never mind, if my changes to `inline` add the `inline` keyword, then we can remove the redefinition __inline__ and __inline. All that to say your original suggestion is better than my follow up. -- Thanks, ~Nick Desaulniers -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
