Question

I have this problem with signal():

This code compiles fine:

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

void terminate( int param )
{
  printf ( "Terminating program...\n" );
  exit( 1 );
}

int main()
{
    signal( SIGTERM, terminate );
    return 0;
}

The following code, however, throws this error:

g++ -Wall -c -g goober.cpp
goober.cpp: In member function `void GOOBER::yarrgh()':
goober.cpp:5: error: argument of type `void (GOOBER::)(int)' does not match `
   void (*)(int)'
make: *** [goober.o] Error 1

goober.h:

#ifndef GOOBER_H
#define GOOBER_H

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

using namespace std;

class GOOBER {
public:
    GOOBER(){}
    ~GOOBER(){}
    void yarrgh();
    void terminate( int param );
};

#endif

goober.cpp:

#include "goober.h"

void GOOBER::yarrgh()
{
    signal( SIGTERM, terminate );
}

void GOOBER::terminate( int param )
{
    printf( "Terminating program...\n" );
    exit( 1 );
}

driver.cpp:

#include "goober.h"

using namespace std;

int main()
{
    GOOBER G;
    G.yarrgh();

    return 0;
}

I don’t see any difference in the code, other than I’m calling signal() in a member. Any ideas what’s wrong, and how to fix it?

Answer 1

You need to declare your terminate() function as static:

class GOOBER {
    // ...
    static void terminate(int param);
};

This is because that as a non-static member function, the terminate() function expects to be passed the (hidden) this parameter to point to some instance of the object. Since the signal mechanism doesn’t know about this (or about anything much of C++), you need to use a static function so that there is no hidden this parameter.