Re: toolchain/46033: gcc miscompiles tcl config test

[David Brownlee <abs%netbsd.org@localhost>]

The following reply was made to PR toolchain/46033; it has been noted by GNATS.

From: David Brownlee <abs%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: port-vax%netbsd.org@localhost
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.