带返回值的宏--({})的妙用

定义

格式如下：

#define your_macros(x) ({ \ type return_value; \ .... \ return_value; \ })

示例1

#define myprefix_asctime(tp) \ ({ \ char *tmpbuf = __builtin_alloca(64) \ asctime_r(tp, tmpbuf); \ tmpbuf; \ })

参见文章https://blog.csdn.net/luowutong/article/details/156825070

示例2

#define _socket_dup(fd) \ ({ \ int _dup_s = (fd); \ (fd) = -1; \ _dup_s; \ })

参见https://blog.csdn.net/luowutong/article/details/156113831

示例3

#define kill_dependency(Y) \ __extension__ \ ({ \ __auto_type __kill_dependency_tmp = (Y); \ __kill_dependency_tmp; \ })

参见https://blog.csdn.net/luowutong/article/details/156696081