The __format_arg attribute tells gcc that it can use a specific argument to the annotated function as the format string for the purpose of type-checking a surrounding __printf function call, e.g.
sprintf(buf, fmtcheck(what->ever, "%d %lx", 0), i, m) makes gcc check that i and m are indeed an int and a long; with sprintf(buf, what->ever, i, m) the compiler cannot do any type checking. Signed-off-by: Rasmus Villemoes <[email protected]> --- include/linux/compiler-gcc.h | 1 + include/linux/compiler.h | 4 ++++ 2 files changed, 5 insertions(+) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index bb78e5bdff26..69a233f9fa26 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -128,6 +128,7 @@ #define __maybe_unused __attribute__((unused)) #define __always_unused __attribute__((unused)) #define __mode(x) __attribute__((mode(x))) +#define __format_arg(n) __attribute__((format_arg(n))) /* gcc version specific checks */ diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 478914ad280b..2c8793f72fb0 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -631,4 +631,8 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s #define __format_template(x) #endif +#ifndef __format_arg +#define __format_arg(n) +#endif + #endif /* __LINUX_COMPILER_H */ -- 2.11.0
