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This non-compliant code example moves the finite state machine out of the signal handler, making the handler asynchronous-safe.
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#include <signal.h>
volatile sig_atomic_t sig1 = 0;
volatile sig_atomic_t sig2 = 0;
void handler(int signum) {
if (signum == SIGUSR1) {
sig1 = 1;
}
else if (signum == SIGUSR2) {
sig2 = 1;
}
}
int main(void) {
int state = 0;
signal(SIGUSR1, handler);
signal(SIGUSR2, handler);
while (state != 2) {
/* do nothing or give up CPU for a while */
if (state == 0 && sig1) {
state = 1;
sig2 = 0;
}
if (state == 1 && sig2) {
state = 2;
}
}
/* ... */
return 0;
}
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