On Sun, 3 Feb 2019 20:24:00 +0100 Rasmus Villemoes <li...@rasmusvillemoes.dk> wrote:
> BUILD_BUG_ON() is a little annoying, since it cannot be used outside > function scope. So one cannot put assertions about the sizeof() a > struct next to the struct definition, but has to hide that in some > more or less arbitrary function. > > Since gcc 4.6 (which is now also the required minimum), there is > support for the C11 _Static_assert in all C modes, including gnu89. So > add a simple wrapper for that. > > _Static_assert() requires a message argument, which is usually quite > redundant (and I believe that bug got fixed at least in newer C++ > standards), but we can easily work around that with a little macro > magic, making it optional. > > For example, adding > > static_assert(sizeof(struct printf_spec) == 8); > > in vsprintf.c and modifying that struct to violate it, one gets > > ./include/linux/build_bug.h:78:41: error: static assertion failed: > "sizeof(struct printf_spec) == 8" > #define __static_assert(expr, msg, ...) _Static_assert(expr, "" msg "") > > godbolt.org suggests that _Static_assert() has been support by clang > since at least 3.0.0. > It would be (very) nice to actually use this macro in a few places so it gets its build testing while in -next.
