On Thu, 2018-06-07 at 11:32 -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 +72,22 @@
> * -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
> +#define __inline inline
> #else
> /* A lot of inline functions can cause havoc with function tracing */
> -#define inline inline __attribute__((unused)) notrace
> -#define __inline__ __inline__ __attribute__((unused)) notrace
> -#define __inline __inline __attribute__((unused)) notrace
> +#define inline inline __attribute__((unused, gnu_inline)) notrace
> +#define __inline__ inline
> +#define __inline inline
> #endif
Perhaps move these last 2 defines below the #endif
as they are common to both cases
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
!defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
#define inline inline __attribute__((always_inline, unused, gnu_inline)) notrace
#else
/* A lot of inline functions can cause havoc with function tracing */
#define inline inline __attribute__((unused, gnu_inline)) notrace
#endif
#define __inline__ inline
#define __inline inline
#define __always_inline inline __attribute__((always_inline))
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