Bug 770892

Description of problem:

This is a side-effect of tracking down problems from bug 770782 but I think that I mention that for a completness.

With debugging code turned on mutt may get sometimes bogus messages
when saving base64 encoded attachments.  Like that:

handler.c:310 [mutt_decode_base64()]: didn't get a multiple of 4 chars.

This is from this code:

  while (len > 0)
  {
    for (i = 0 ; i < 4 && len > 0 ; len--)
    {
      if ((ch = fgetc (s->fpin)) == EOF)
        break;
      if (ch >= 0 && ch < 128 && (base64val(ch) != -1 || ch == '='))
        buf[i++] = ch;
    }
    if (i != 4)
    {
      dprint (2, (debugfile, "%s:%d [mutt_decode_base64()]: "
                  "didn't get a multiple of 4 chars.\n", __FILE__, __LINE__));
      break;
    }
......
  }

and a message may be bogus because it will happen also when i is 0 - which is definitely a multiple of 4 and means that we just finished decoding.

That does happen in "real life" but it is easy to construct simple demo example.
Just put into an attachment results of 'echo -n abc | base64', which comes to YWJj, followed by a new line.  Then the second run of 'while' loop starts with len set to 1, nothing is put in buf so i ends as 0 and 4*0 is deemed not to be a multiple of 4. :-)

To fix simply add 'i == 0 && break;' before "dprint" line.

Version-Release number of selected component (if applicable):
mutt-1.5.21

Additional info:
mutt as shipped in Fedora does not have a debugging compiled in (which would be useful on occasions) and besides this is only a suggestion that something went wrong when nothing like that really happened.