bug#16901: 24.3.50; emacs_backtrace.txt

[Ken Brown]

On 3/3/2014 10:45 PM, Eli Zaretskii wrote:
> > Date: Mon, 03 Mar 2014 18:20:09 -0500
> > From: Ken Brown <kbrown@cornell.edu>
> > CC: 16901@debbugs.gnu.org, dmantipov@yandex.ru
> >
> > If adj == 0 in line 1596, then we've allocated much more memory than
> > we needed, and the next call to malloc (line 1602) allocates even
> > more.  And if adj == 1 in line 1596, then we've allocated exactly as
> > much memory as we needed, so there's no need to call malloc again in
> > line 1602.
>
> Thanks for reviewing.
>
> These are further optimizations, and can (and probably should) be done
> in separate commits.  But you aren't saying that the previous code was
> correct, are you?

No, I think it was clearly wrong.  By accident, however, it probably 
worked most of the time and didn't waste memory, since adj is usually 0.

When/if you do the optimizations I suggested, I think it would clarify 
the code if `adj' were used to represent the actual adjustment needed, 
something like this:

  adj = (uintptr_t) alignment - result % alignment;
  if (adj == alignment)
    adj = 0;

Ken