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<2023-04-10 Mon>
[ os ]

POSIX Signals

Signals are a way to notify running programs of events to trigger a response, such as quitting or error handling. They are used in Unix and POSIX-compliant operating systems and represent a form of inter-process communication (IPC).

Setting a signal handler in C

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>

void sig_segv_handler(int signum) { printf("SEGV ignored.\n"); }

int main(int argc, char** argv)
{
    /* int signal () (int signum, void (*func)(int)) */
    signal(SIGSEGV, sig_segv_handler);

    // cause intentional segmentation fault (also gets picked up by gcc as stack-smashing)
    float* arr = (float*) malloc(sizeof(float) * 3);
    arr        = (float[3]) {0.4f, 0.3f, 3.2f};
    arr[3]     = 11.0f;
    printf("%.1f %.1f %.1f\n", arr[0], arr[1], arr[2]);
}

Compile with gcc -O0 handler.c -o handler -fno-stack-protector.

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