Signal handler is not getting called in main function

Question

I am trying to study how signal handlers work. I have written code where i cause an alarm signal to raise once in every 100us. But, the signal is not raised. Here is the code :

 #include <signal.h> #include <ucontext.h> #include <sys/time.h> #include<unistd.h> #include<setjmp.h> #include<stdio.h> void handler(int signum, siginfo_t *ptr, ucontext_t *old_context) { printf("inside handler"); } int main() { struct itimerval itv; struct sigaction act; act.sa_handler = handler; act.sa_flags=SA_RESTART|SA_SIGINFO; sigaction(SIGVTALRM, &act, 0); itv.it_interval.tv_sec=0; itv.it_interval.tv_usec=100; itv.it_value.tv_sec = 0; itv.it_value.tv_usec = 100; setitimer(ITIMER_VIRTUAL, &itv, NULL); //engage timer int i=0; while(i<=100) { printf("main\n"); i++; } }

can some one explain what i am doing wrong?

Thanks

fbafelipe · Accepted Answer · 2011-09-18 05:13:30Z

Your loop is probably taking less than 100us to run, try this:

volatile int i=0; while(i<=100000000) { //printf("main\n"); i++; }

I removed the printf so the output is not flooded, and made i volatile so the compiler won't optimize the loop.

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