地：Linux系统内核中判断大小的宏

/*
* min()/max() macros that also do
* strict type-checking.. See the
* "unnecessary" pointer comparison.
*/
#define min(x,y) ({ \
typeof(x) _x = (x); \
typeof(y) _y = (y); \
(void) (&_x == &_y); \
_x < _y ? _x : _y; })

#define max(x,y) ({ \
typeof(x) _x = (x); \
typeof(y) _y = (y); \
(void) (&_x == &_y); \
_x > _y ? _x : _y; })

/*
* ..and if you can't take the strict
* types, you can specify one yourself.
*
* Or not use min/max at all, of course.
*/
#define min_t(type,x,y) \
({ type __x = (x); type __y = (y); __x < __y ? __x: __y; })
#define max_t(type,x,y) \
({ type __x = (x); type __y = (y); __x > __y ? __x: __y; })