From mboxrd@z Thu Jan  1 00:00:00 1970
From: gustav@virtutech.se
To: gcc-gnats@gcc.gnu.org
Cc: mattias@virtutech.se
Subject: c/4210: bad warning with dead code
Date: Mon, 03 Sep 2001 11:36:00 -0000
Message-id: <20010903182858.26588.qmail@sourceware.cygnus.com>
X-SW-Source: 2001-09/msg00040.html
List-Id: <gcc-prs.sourceware.org>

>Number:         4210
>Category:       c
>Synopsis:       bad warning with dead code
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Sep 03 11:36:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     gustav@virtutech.se
>Release:        GNU C version 3.0.1 20010626 (prerelease) (i386-pc-linux-gnu)
>Organization:
>Environment:

>Description:
gcc outputs a warning about shifts >= width of type inside
dead code when that code is dead because of a const
variable. This can easily happen in autogenerated code, or
when you do operations on preprocessor defines.
>How-To-Repeat:
Compile the following with -Wall -O2:

int rol0(int a)
{
        const int b = 0;
	if (b) {
		a = (a << b) | (a >> (8 * sizeof a - b));
        }
	return a;
}
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: