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Editorial Team
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Asked: 2026-05-15T05:37:09+00:00

I wrote a program some time ago (Mac OS X, C++, SDL, FMOD) and

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I wrote a program some time ago (Mac OS X, C++, SDL, FMOD) and it perfomed rather good. But lately I wanted to extend its functionality and added some more code to it. And now, when I run it and try to test the new functionality, the program crashes with SIGABRT.

Looking into debugger, on function stack I see:

  • _kill
  • kill$UNIX2003
  • raise
  • __abort
  • __stack_chk_fail
  • odtworz <– my function that was was modified

As far as I know, “__stack_chk_fail” indicates a stack overflow. But that’s not the weirdest thing about it. In this function “odtworz”, I have some code like this:

...

koniec = 0;
while ( koniec == 0 ) {
    ...
    if (mode == 1) {
        ...
    }
    else if (mode == 2) {
        ...
    }
    else if (mode == 3) {
       piesniOrkiestrowe[0] = '\0'; 
       while ( piesniOrkiestrowe[0] == '\0' ) { 
           losowaPiesn(); 
           char * piesnOrkiestrowa = szukajPiesniOrkiestrowej(); 
           if ( piesnOrkiestrowa != NULL ) 
              strcpy(piesniOrkiestrowe, piesnOrkiestrowa); 
       } 
       char nowyPiesnPlik[25]; 
       sprintf(nowyPiesnPlik, "%sorch/%s", PIESNI_DIR.c_str(), piesniOrkiestrowe);
    }
}

mode is a global variable and is set to value “2” in a function before. And now imagine – if I delete the third if statement (mode == 3) which never gets executed in this mode, the program doesn’t crash! Deleting code that doesn’t even get to be executed helps the situation!

Now, I don’t want to delete this code because it’s for other mode of my program. And it works fine there. So any hints where I can search? What could be possibly wrong with this?

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1 Answer

  1. Editorial Team

    It is not a stack overflow error. __stack_chk_fail is called when stack frame corruption is detected. The traditional way to smash the stack is a buffer overflow. The code that causes it is not in your snippet, it is in the dots.

    After updating the question with code from a comment: both the strcpy and the sprintf calls are excellent candidates for stack corruption. The buffer overflow problem I mentioned in my original answer. Taking a guess: nowyPiesnPlik looks very small. The sprintf() function will write too many characters to the buffer and overwrite the “canary”. When the canary gets stomped on, the runtime will whistle fowl 🙂

    You could make the array bigger. Not a real solution, use safe alternatives for these functions, like snprintf(). I’ll avoid mentioning strncpy().

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