Re: c/10339: strncmp generates imPure code

[Andreas Schwab <schwab@suse.de>]

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The following reply was made to PR optimization/10339; it has been noted by GNATS.

From: Andreas Schwab <schwab@suse.de>
To: Michael Ubell <ubell@mindspring.com>
Cc: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>,
	Wolfgang Bangerth <bangerth@ices.utexas.edu>, gcc-bugs@gcc.gnu.org,
	gcc-gnats@gcc.gnu.org
Subject: Re: c/10339: strncmp generates imPure code
Date: Mon, 07 Apr 2003 21:24:46 +0200

 Michael Ubell <ubell@mindspring.com> writes:
 
 |> > I suspect the extra byte read is actually not relevant for the result,
 |> > and because of alignment, gcc knows the second problem cannot occur,
 |> > but I have neither a SPARC nor SPARC knowledge to test that.
 |> > 
 |> 
 |> Actually if you make the compare string longer you can get it
 |> to look at an arbitrary number of bytes passed the allocated part,
 |> so I think this could fault if you set it up right.  Also in
 |> the original problem, the first argument was not allocated locally
 |> so the compiler would have no idea how big or what its alignment
 |> was.  (In fact it was in a loop comparing strings from an array.)
 
 Could you please provide a test case that actually shows the problem?
 
 Andreas.
 
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 Andreas Schwab, SuSE Labs, schwab@suse.de
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