C89 static assert

static.h

// usage: FTG_STATIC_ASSERT(1==0)
// error message contains "assertion_at_line_xxx"
//
// usage: FTG_STATIC_ASSERT_MSG(1==0, one_is_not_zero)
// error message contains: "one_is_not_zero"
//
// tested on GCC, Clang, MSVC 98 and MSVC 2015
//



#define FTG_STATIC_ASSERT_MSG(x, msg) typedef int FTG__StaticAssert_##msg[(x) ? 1 : -1]
#define FTG__STATIC_ASSERT_3(x,L) FTG_STATIC_ASSERT_MSG(x, assertion_at_line_##L)
#define FTG__STATIC_ASSERT_2(x,L) FTG__STATIC_ASSERT_3(x,L)
#define FTG_STATIC_ASSERT(x) FTG__STATIC_ASSERT_2(x,__LINE__)