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Re: crash: x_error_quitter

From: David Kastrup
Subject: Re: crash: x_error_quitter
Date: Wed, 16 May 2007 23:42:40 +0200
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/23.0.51 (gnu/linux)

Eli Zaretskii <address@hidden> writes:

>> From: David Kastrup <address@hidden>
>> Date: Wed, 16 May 2007 08:58:42 +0200
>> Cc: address@hidden, address@hidden, address@hidden
>> I think that if we are compiling with -g, we should also enable the
>> -fno-crossjumping option.  Drawback is that this will cause slightly
>> different code to be produced.
> Why not use -fno-crossjumping even if we compile without -g?  I can
> hardly believe this will cause any visible slowdown, as Emacs does not
> have tight inner loops anywhere.

We are not even talking tight inner loops here.  We are talking calls
of functions that never return.  Those can't happen too often (unless
there is some exception mechanism involved, or garbage compaction of
the stack, a tactique that some Scheme runtimes use for implementing
continuations), or the stack will overflow.

This is just a mechanism for squeezing out a few bytes.

Using -fno-crossjumping always (when supported by the compiler, of
course) would probably save us some dozen man hours of erroneous
post-mortem debugging.  The main disadvantage is that it makes the
compilation look ugly, as if Emacs were some special application
needing special compiler options.  In my opinion, crossjumping should
likely only be enabled for -O5 or greater.  Something like that.

David Kastrup, Kriemhildstr. 15, 44793 Bochum

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