c/10339: strncmp generates imPure code

[Falk Hueffner]

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

From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
To: Michael Ubell <ubell@mindspring.com>
Cc: 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: 07 Apr 2003 21:27:02 +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 perhaps provide such an example? For your original example,
 gcc knows that malloc returns only aligned pointers.
 
 -- 
 	Falk