NetBSD Problem Report #46033

From martin@duskware.de  Thu Feb 16 21:46:24 2012
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Date: Thu, 16 Feb 2012 21:46:23 +0000 (UTC)
From: martin@NetBSD.org
Reply-To: martin@NetBSD.org
To: gnats-bugs@gnats.NetBSD.org
Subject: gcc miscompiles tcl config test
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>Number:         46033
>Category:       toolchain
>Synopsis:       gcc miscompiles tcl config test
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 16 21:50:00 +0000 2012
>Last-Modified:  Tue May 01 11:30:18 +0000 2012
>Originator:     Martin Husemann
>Release:        NetBSD 5.99.65
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD dead-to-the-world.duskware.de 5.99.65 NetBSD 5.99.65 (DEAD) #51: Tue Feb 14 22:38:47 CET 2012 martin@night-porter.duskware.de:/usr/src/sys/arch/vax/compile/DEAD vax
Architecture: vax
Machine: vax
>Description:

With gcc 4.5.3 the following (closely based on a config test from pkgsrc/lang/tcl)
fails to complete:

#include <ctype.h>
#include <stdlib.h>
#include <stdio.h>

#define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
#define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
#define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))

int main ()
{
	int i;

	for (i = 0; i < 256; i++) {
		printf("testing with i = %d\n", i);
		if (XOR (islower (i), ISLOWER (i))
		    || toupper (i) != TOUPPER (i))
			exit(2);
	}
	printf("done\n");
	return 0;
}

Compiling this causes strange warnings 

conftest.c:16:7: warning: 'iftmp.4' may be used uninitialized in this function

and the value of i is always 0.

>How-To-Repeat:
s/a
>Fix:
n/a

>Audit-Trail:
From: David Brownlee <abs@netbsd.org>
To: gnats-bugs@netbsd.org
Cc: port-vax@netbsd.org
Subject: Re: toolchain/46033: gcc miscompiles tcl config test
Date: Tue, 1 May 2012 12:30:14 +0100

 Had a quick play and found something interesting - this only shows up
 under the native compiler, not a cross compiler

 ./build.sh -m vax ... tools
 .../vax--netbsdelf-gcc -O2 -c conftest.c ; scp conftest.o root@vax
 vax# cc -o a.out conftest.o ; ./a.out
 [... valid output ...]

 Not that this particularly helps, just to show that the test shows up
 an issue in the compiler compiling gcc source, rather than itself :)
 (Tested with -O2, -O and no -O)

 [original source below]
 > With gcc 4.5.3 the following (closely based on a config test from pkgsrc/=
 lang/tcl)
 > fails to complete:
 >
 > #include <ctype.h>
 > #include <stdlib.h>
 > #include <stdio.h>
 >
 > #define ISLOWER(c) ('a' <=3D (c) && (c) <=3D 'z')
 > #define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
 > #define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
 >
 > int main ()
 > {
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0int i;
 >
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0for (i =3D 0; i < 256; i++) {
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0printf("testing wi=
 th i =3D %d\n", i);
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0if (XOR (islower (=
 i), ISLOWER (i))
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0|| t=
 oupper (i) !=3D TOUPPER (i))
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
 =A0 =C2=A0exit(2);
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0}
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0printf("done\n");
 > =C2=A0 =C2=A0 =C2=A0 =C2=A0return 0;
 > }
 >
 > Compiling this causes strange warnings
 >
 > conftest.c:16:7: warning: 'iftmp.4' may be used uninitialized in this fun=
 ction
 >
 > and the value of i is always 0.

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