//----------------------------------------------------------------
//	signal4.cpp
//
//	This program will attempt to dereference a null pointer,
//	but beforehand it installs a signal-handler for SIGSEGV. 
//	Now the signal-handler will 'exit' rather than 'return',
//	but before it exits, it displays a portion of the stack. 
//
//	  compile-and-link using: $ g++ signal4.cpp -o signal4
//
//	programmer: ALLAN CRUSE
//	written on: 20 MAR 2006
//----------------------------------------------------------------

#include <stdio.h>	// for printf()
#include <signal.h>	// for signal()
#include <stdlib.h>	// for exit()

void upon_signal( int signo )
{
	printf( "\nCaught signal number %d \n\n", signo );

	int	*tos = &signo;
	for (int k = 1; k <= 20; k++)
		{
		int	i = 20 - k;	
		printf( "%08X: %08X =tos[%d] \n", &tos[i], tos[i], i );
		}
	printf( "\n" );

	exit( signo );
}

int main( int argc, char *argv[] )
{
	signal( SIGSEGV, upon_signal );

	int	*ptr = NULL;

	int	x = *ptr;

	printf( "\nx = %08X \n\n", x );
}