//-------------------------------------------------------------------
//	sigdemo.cpp
//
//	This program demonstrates the basic Linux signal-handling
//	mechanism: it calls the 'sigaction()' library-function to  
//	install our own signal-handling routine for any 'SIGSEGV'
//	signals (Segmentation Violation), then calls a sunroutine
//	that triggers the generation of just this type of signal.
//	You can use our 'run.cpp' program to view the exit-status
//	and thereby verify that exit was from the signal-handler.
//
//		compile using:  $ make sigdemo
//		execute using:  $ run sigdemo
//
//	programmer: ALLAN CRUSE
//	written on: 03 MAY 2005
//-------------------------------------------------------------------

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


void myhandler( int signum, struct siginfo *si, void *appcontext )
{
	printf( "signal %d was caught!\n", signum );
	exit( 1 );
}


void myfunction( char *ptr )
{
	// write 0 to the specified memory-address 
	*ptr = 0;
}


int main( int argc, char **argv )
{
	// declares a 'sigaction' structure 
	struct sigaction	sa = {0};

	// initializes 'sigaction' structure 	
	sigemptyset( &sa.sa_mask );
	sa.sa_flags = SA_SIGINFO;
	sa.sa_sigaction = myhandler;

	// installs our handler for SIGSEGV signals
	sigaction( SIGSEGV, &sa, NULL );
	
	// calls a function that will use an invalid address
	myfunction( NULL );

	// returns exit-status 0 (assuming we ever get here)
	exit( 0 );
}