c++ 编译时检测结构体大小的的宏定义写法

template <bool>
struct CompileAssert {

};

#define COMPILE_ASSERT(expr, msg) \
    typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1]

} //endof namespace

 1 #define CAT_TOKEN_1(t1,t2) t1##t2
 2 #define CAT_TOKEN(t1,t2) CAT_TOKEN_1(t1,t2)
 3 
 4 #define COMPILE_ASSERT(x)   5                     enum {CAT_TOKEN (comp_assert_at_line_, __LINE__) = 1 / !!(x) };
 6 
 7 #ifndef CHECK_SIZE
 8 #define CHECK_SIZE(type, size) extern int sizeof_##type##_is_##size [!!(sizeof(type)==(size_t)size) - 1]
 9 #endif//CHECK_SIZE
10 
11 #ifndef CHECK_OFFSET
12 #define CHECK_OFFSET(type, member, value) 13         extern int offset_of_##member##_in_##type##_is_##value 14     [!!(__builtin_offsetof(type,member)==((size_t)(value))) - 1]
15 #endif//CHECK_OFFSET