container, error: update error handling

[eriksjolund]

What is the preferred way to write a check that indicates that a failure is not expected and that such a failure would indicate a programming errror?

One way is to write assert() (but such a check is only active for an executable that was compiled with the debug option enabled)

For example:

  assert(err != NULL);
  assert(*err != NULL);

This is another way:

if (err == NULL || *err == NULL) {
  // programming error
  _exit(EXIT_FAILURE);
}

I prefer assert() slightly more.

[giuseppe]

for the rest of the code, we used something like return crun_make_error (err, 0, "internal error");

because there is the risk that an assert would produce output that is ignored (when setting up the child process)

[eriksjolund]

I pushed a new version that makes less changes.

Right now

    {
      // Internal error
      return 0;
    }

Should maybe be

    {
      // Internal error
      return -1;
    }

to make it more robust. I'm not sure what's best.

[giuseppe]

LGTM