// Compile with gcc -Wall -pedantic-errors -std=gnu99 foo.c
//
#include <stdio.h>
#include <setjmp.h>
#include <signal.h>

// Pointer to functions like void f(void)
//
typedef void (*Func)(void);

// Store where to go when SIGSEGV caught
//
static sigjmp_buf jumpTarget;

// Called when SIGSEGV caught
//
static void sigHandler(int sig) {
  siglongjmp(jumpTarget, sig);
}

// Execute the supplied function, return 0 for success and 1 for SIGSEGV
//
int catchCrash(Func f) {
  struct sigaction oldAction;
  struct sigaction newAction;

  // Remember the old SIGSEGV handler and set a new handler
  newAction.sa_flags = 0;
  newAction.sa_handler = sigHandler;
  sigemptyset(&newAction.sa_mask);
  sigaction(SIGSEGV, &newAction, &oldAction);

  // Crashing code ends up inside this block
  if ( __extension__ sigsetjmp(jumpTarget, 1) != 0 ) {
    return 1; // crash detected
  }

  // Execute the function: maybe crash, maybe not
  f();

  // Restore the old handler
  sigaction(SIGSEGV, &oldAction, NULL);
  return 0;
}

// Innocuous function
//
void sayHello(void) {
  printf("Hello World\n");
}

// Attempt to write to address zero
//
void writeZero(void) {
  int *p = NULL;
  *p = 42;
}

// Attempt to read from address zero
//
void readZero(void) {
  int *p = NULL;
  printf("Read: %d\n", *p);
}

// Attempt to execute code at address zero
//
void jmpZero(void) {
  Func f = NULL;
  f();
}

int main(void) {
  printf("catchCrash(sayHello) returned %d\n", catchCrash(sayHello));
  printf("catchCrash(writeZero) returned %d\n", catchCrash(writeZero));
  printf("catchCrash(readZero) returned %d\n", catchCrash(readZero));
  printf("catchCrash(jmpZero) returned %d\n", catchCrash(jmpZero));
  return 0;
}