Question

I probably missed something but just wanna ask.. I found this code in the book Advanced Linux programming:

    char* get_self_executable_directory ()
    {
      int rval;
      char link_target[1024];
      char* last_slash;
      size_t result_length;
      char* result;
      /* Read the target of the symbolic link /proc/self/exe. */
      rval = readlink (“/proc/self/exe”, link_target, sizeof (link_target));
      if (rval == -1)
        /* The call to readlink failed, so bail. */
        abort ();
      else
        /* NUL-terminate the target. */
        link_target[rval] = ‘\0’;
      /* We want to trim the name of the executable file, to obtain the
      directory that contains it. Find the rightmost slash. */
      last_slash = strrchr (link_target, ‘/’);
      if (last_slash == NULL || last_slash == link_target)
        /* Something strange is going on. */
        abort ();
      /* Allocate a buffer to hold the resulting path. */
      result_length = last_slash - link_target;
      result = (char*) xmalloc (result_length + 1);
      /* Copy the result. */
      strncpy (result, link_target, result_length);
      result[result_length] = ‘\0’;
      return result;
    }

And my question is, doesn’t this function return a dangling pointer?

Answer 1

It returns a pointer and expects that deallocation will be done in client code. When you see functions that return pointers you always have to ask yourself (well really the author…) whether or not ownership of the memory (that is the responsibility to deallocate it) passes to the function’s client and if so how exactly it should be freed.