Re: `message' not outputting the newline "atomically"

[Paul Eggert]

Eli Zaretskii wrote:
> an error message could legitimately be output piecemeal.

All such error messages in Emacs are output with a trailing newline right away, 
so there is no significant problem here. The trailing newline is standard 
practice, both in Emacs and elsewhere.  For example, consider the following code 
(taken from src/pdumper.c):

  static void
  dump_fingerprint (const char *label, unsigned char const *xfingerprint)
  {
    fprintf (stderr, "%s: ", label);
    for (int i = 0; i < 32; ++i)
      fprintf (stderr, "%02x", (unsigned) xfingerprint[i]);
    fprintf (stderr, "\n");
  }

Here, GNU/Linux Emacs would issue 34 'write' system calls if stderr were using 
_IONBF (and the output line could be interleaved with other output lines, 
possibly causing confusion), whereas GNU/Linux Emacs issues just one 'write' 
system call now that stderr uses _IOLBF (thus avoiding the confusion).

I don't see any significant problem with line-buffering here, or anywhere else 
that Emacs outputs to stderr. And I've looked at quite a few uses.

> You will audit the sources from now to eternity?

An audit is not necessary. I volunteered to audit only to allay any concerns 
with my assertion that this change is OK. If these concerns cannot be allayed by 
any such evidence, then of course an audit would be a waste of time.