_XOPEN_SOURCE宏能够改变signal函数的行为，这是如何做到的？#include stdio.h#include signal.hvoid si
_XOPEN_SOURCE宏能够改变signal函数的行为，这是如何做到的？
#include <stdio.h>
#include <signal.h>
void sig_int(int signo)
{
printf("caught SIGINT\n");
}
int main()
{
signal(SIGINT, sig_int);
for (; ; );
return 0;
}
默认情况下，如果输入多个中断键，那么能够捕捉所有的中断信号。
但是如果用 gcc test.c -D _XOPEN_SOURCE 编译，那么只能捕捉一次中断信号，当输入第二个中断键时程序就退出了。
请问_XOPEN_SOURCE 这个宏是如何做到改变signal函数的行为的，就我理解，这些宏定义不是最多只能让程序多包含一些特定的函数声明吗?
[解决办法]信号很复杂，用signal会遇到很多的移植性和可靠性的问题，建议使用sigaction;
至于楼主遇到的情况，在Linux函数手册中有详细的描述
PORTABILITY
The original Unix signal() would reset the handler to SIG_DFL, and System V (and the Linux kernel and
libc4,5) does the same. On the other hand, BSD does not reset the handler, but blocks new instances of
this signal from occurring during a call of the handler. The glibc2 library follows the BSD behaviour.
If one on a libc5 system includes <bsd/signal.h> instead of <signal.h> then signal() is redefined as
__bsd_signal and signal has the BSD semantics. This is not recommended.
If one on a glibc2 system defines a feature test macro such as
_XOPEN_SOURCE or uses a separate sysv_sig-
nal function, one obtains classical behaviour. This is not recommended.
Trying to change the semantics of this call using defines and includes is not a good idea. It is better
to avoid signal() altogether, and use sigaction(2) instead.
