c - 是 sigsegv 的模棱两可的行为

Question

注意:当我像 raise(SIGSEGV); 那样引发 SIGSEGV 时，SEGSEGV 会被阻止，但在取消引用 NULL 指针或内存冲突时不会。这里有什么问题？

代码:

void sig_handler(int signo)
{
       psignal(signo,"i am in sig_handler\n");
}

int main()
{
    sigset_t intmask;
    int c = 0, *p = NULL;

    if((signal(SIGSEGV , sig_handler)) == SIG_ERR)
             perror("signal call is failed\n");
    if ((sigemptyset(&intmask) == -1) || (sigaddset(&intmask, SIGSEGV) == -1))    
          perror("Failed to initialize the signal mask");
    sigprocmask(SIG_BLOCK, &intmask, NULL);
    fprintf(stdout, "SIGINT signal blocked\n");
    c = *p;
}

Answer 1

sigprocmask() 的手册页有答案:

If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are generated while they are blocked, the result is undefined, unless the signal was generated by kill(2), sigqueue(3), or raise(3).