/* signal_cpp.cpp
 * Stephanie Taylor
 * There is a difference between exceptions and signals
 * In particular, if an exception is caught (even all the way at the top
 * of the call stack), then any object on the stack will have its 
 * destructor called. This does not happen for a signal.
 */

#include <iostream>
#include <signal.h>
#include <stdexcept>
using namespace std;

class hammer {
    private:
    
    int *field_a;
    
    public:
    
    // constructor
    hammer() {
        cout << "constructing a hammer" << endl;
        field_a = NULL;
    }
    
    // assume that the field has been given a value that isn't
    // null, and print it out.
    void print_hammer_val() {
      printf( "in print_hammer_val\n" );
      // If we use an exception, things will go better.
      //if (field_a == NULL) {
        //printf( "about to throw\n" );
        //throw invalid_argument("don't derefence null pointers!");
      //}
      // If the if-statement above is commented out, then
      // we will have a signal instead.
      // The dereference in the printf causes a segmentation fault.
      cout << *field_a << endl;
    }

    // destructor
    ~hammer() {
        cout << "destructing a hammer" << endl;
    }    
};

void seghandler(int signal) {
    printf("\nCaught seg fault %d\n", signal);
    //return;
    exit(-1);
}

int main() {
    signal(SIGSEGV, seghandler);
    try {
        hammer h;
        h.print_hammer_val();    
    }
    catch (invalid_argument) {
        cout << "caught exception" << endl;
    }
}