wrong code generated with -O
>Submitter-Id: net
>Originator: Konstantin Kivi
>Organization:
>Confidential: no
>Synopsis: wrong code generated with -O
>Severity: serious
>Priority: medium
>Category: optimization
>Class: wrong-code
>Release: 3.0.4 (Debian testing/unstable)
>Environment:
System: Linux konst 2.4.20 #4 SMP ðÎÄ óÅÎ 22 18:41:18 MSD 2003 i686 unknown
Architecture: i686
host: i386-pc-linux-gnu
build: i386-pc-linux-gnu
target: i386-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,proto,objc --prefix=/usr --infodir=/share/info --mandir=/share/man --enable-shared --with-gnu-as --with-gnu-ld --with-system-zlib --enable-long-long --enable-nls --without-included-gettext --disable-checking --enable-threads=posix --enable-java-gc=boehm --with-cpp-install-dir=bin --enable-objc-gc i386-linux
>Description:
in the example below gcc generate incorrect code in optimization mode
>How-To-Repeat:
Script started on Fri May 14 15:57:37 2004
konst@konst://.../Bug>cat bbug.c
struct a {
char t[2];
int b;
} ;
struct aa {
char t[2];
} ;
int main()
{
struct a A;
struct aa AA;
A.t[0]=0xFF;
A.t[1]=0xF9;
if((unsigned char )A.t[0]==0xFF &&
(unsigned char)A.t[1]==0xF9 ) {
puts("A Ok");
}
AA.t[0]=0xFF;
AA.t[1]=0xF9;
if((unsigned char )AA.t[0]==0xFF &&
(unsigned char)AA.t[1]==0xF9 ) {
puts("AA Ok");
}
return 0;
}
konst@konst://.../Bug>cat makefile
.PHONY: good bad all
all: good bad
good:
gcc -Wall bbug.c -o good_prog
bad:
gcc -Wall -O bbug.c -o bad_prog
konst@konst://.../Bug>make
gcc -Wall bbug.c -o good_prog
bbug.c: In function `main':
bbug.c:23: warning: implicit declaration of function `puts'
gcc -Wall -O bbug.c -o bad_prog
bbug.c: In function `main':
bbug.c:22: warning: comparison is always 0
bbug.c:23: warning: implicit declaration of function `puts'
konst@konst://.../Bug>./good_prog
A Ok
AA Ok
konst@konst://.../Bug>./bad_prog
AA Ok
konst@konst://.../Bug>gcc -v
Reading specs from /usr/lib/gcc-lib/i386-linux/2.95.4/specs
gcc version 2.95.4 20011002 (Debian prerelease)
konst@konst://.../Bug>exit
Script done on Fri May 14 15:58:25 2004
Script started on Fri May 14 16:03:25 2004
konst@konst://.../konst>ssh tnuma
DYNIX/ptx(R) V4.5.3 #4 (root): Sat Jun 21 14:39:42 MSD 2003
Copyright 1988 - 2001 Sequent Computer Systems, Inc.
Patents No. 5,185,861; 5,261,053; 5,442,758; 5,608,893; 5,655,122; 5,727,209
No mail.
DYNIX/ptx(R) V4.5.3 #4 (root): Sat Jun 21 14:39:42 MSD 2003
Copyright 1988 - 2001 Sequent Computer Systems, Inc.
Patents No. 5,185,861; 5,261,053; 5,442,758; 5,608,893; 5,655,122; 5,727,209
konst@[tnuma]://...konst>cd Bug
konst@[tnuma]://...Bug>make
gcc -Wall bbug.c -o good_prog
bbug.c: In function `main':
bbug.c:23: warning: implicit declaration of function `puts'
gcc -Wall -O bbug.c -o bad_prog
bbug.c: In function `main':
bbug.c:22: warning: comparison is always 0
bbug.c:23: warning: implicit declaration of function `puts'
konst@[tnuma]://...Bug>./good_prog
A Ok
AA Ok
konst@[tnuma]://...Bug>./bad_prog
AA Ok
konst@[tnuma]://...Bug>gcc -v
Reading specs from /usr/local/lib/gcc-lib/i386-sequent-sysv4/3.3.2/specs
Configured with: ../gcc-3.3.2/configure --with-gnu-as --with-gas --with-gnu-ld --enable-languages=c,c++ --with-stubs
Thread model: single
gcc version 3.3.2
konst@[tnuma]://...Bug>exit
logout
Connection to tnuma closed.
Script done on Fri May 14 16:04:10 2004
>Fix:
do not use -O
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