Re: My Emacs unicode 2 crash again when I do some *Replace String (M-%)*, I give the debug informations under gdb in the attachments.

[Eli Zaretskii <eliz@gnu.org>]

> Cc: rms@gnu.org,  nickrob@snap.net.nz,  handa@m17n.org,  hongyi.zhao@gmail.com,
> 	  emacs-devel@gnu.org
> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Thu, 08 Mar 2007 02:19:41 -0500
> 
> I haven't followed any of gcc's development, but I do have to point out that
> keeping track of source-line numbers through all compilation and
> optimization phases is tremendously difficult and tiresome, even for
> relatively simple optimizations.  And then
> designing/understanding/generating/using debug info is itself a challenge.

I have no doubt that some optimizations cannot avoid hurting
debuggability.  But in the vast majority of programs, the extra 5%-7%
percent of performance those optimizations give you are too low a gain
to justify the terrible price developers need to pay for it.

> So if you want reliable debuggability, avoid optimizations.

The situation is not black and white.  With some cooperation, I'm
positive we could have had an option that enables only those
optimizations which do not severely hamper debugging.

If you ever needed to ship software to a paying customer, you know
that you cannot turn on optimizations only when you ship; you need to
perform the entire testing and QA cycle with the same compilation
options.  Your above suggestion means that the software will be
shipped with unoptimized code, and that is simply unacceptable for
many applications, for performance reasons.