Re: c/7284: incorrectly simplifies leftshift followed by signed power-of-2 division

[Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>]

The following reply was made to PR c/7284; it has been noted by GNATS.

From: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
To: "Al Grant" <AlGrant@myrealbox.com>
Cc: nathan@gcc.gnu.org,  algrant@acm.org,  gcc-bugs@gcc.gnu.org,
	  gcc-prs@gcc.gnu.org,  nobody@gcc.gnu.org,  gcc-gnats@gcc.gnu.org
Subject: Re: c/7284: incorrectly simplifies leftshift followed by signed power-of-2 division
Date: 12 Jul 2002 19:01:43 +0200

 "Al Grant" <AlGrant@myrealbox.com> writes:
 
 > 3.3.7 (something else in ISO, maybe 6.3.7)
 > 
 >   The result of E1 << E2 is E1 left-shifted E2 bit
 >   positions; vacated bits are filled with zeros.
 > 
 > For signed types it says nothing more.
 > 
 > Now if signed left-shift is defined at all, in terms of the
 > representation, I don't see there's any lack of definition in
 > "0x00000080 left-shifted 24 bit positions", it is clearly 0x80000000
 > (of the same type).  So it's defined unless the standard says
 > otherwise, which only C99 seems to.
 
 Defect Report #081 seems to be of interest here
 (http://wwwold.dkuug.dk/JTC1/SC22/WG14/www/docs/dr_081.html). It
 basically states that the behaviour is implementation defined (for any
 signed left shift, not just this case).
 
 -- 
 	Falk