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Mail Archives: djgpp/1999/10/15/15:59:33

From: "John S. Fine" <johnfine AT erols DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: gcc-295 and inline ASM
Date: Fri, 15 Oct 1999 15:40:27 -0400
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Message-ID: <3807832B.4480@erols.com>
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Eli Zaretskii wrote:

> http://egcs.cygnus.com/faq.html#asmclobber

  Thanks, I've been meaning to read that but was too lazy to
search for it.  Clicking on it was much easier :)

  No that I've read it, I'm worried.

  Somewhere (I think it was this newsgroup) I read an example of
how to fix code that had an input in the clobber list.  The fix
was simply to remove it from the clobber list.  That made no
sense, but it seems to work, so I used it some code that I
recompiled for 2.95.  It seemed to work but might be
responsible for some subtle problems I'm having.

  That URL seems to be saying that if a register is both an
input and a clobber of a chunk of inline ASM, then there is
no longer any way to tell the compiler that;  But it is not
safe to pretend the register is only an input.  Instead you
must tell the compiler that it is both an input and an
output.  (Which creates some cases in which the whole thing
must be "volatile" in order to avoid another problem).

  Did I misunderstand the URL?  Or did I misunderstand the
example that was posted here?  Or are people generating
incorrect fixes to these compile-time errors, by simply
removing register from the clobber list?
-- 
http://www.erols.com/johnfine/
http://www.geocities.com/SiliconValley/Peaks/8600/

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