Message-Id: <200001261144.GAA13758@LONG-MARCH.MIT.EDU>
To: pgcc AT delorie DOT com
Cc: liju99 AT MIT DOT EDU
Subject: pgcc 2.95.3 "-O6 -ffast-math" bug
Date: Wed, 26 Jan 2000 06:44:49 EST
From: Ju Li <liju99 AT MIT DOT EDU>
Reply-To: pgcc AT delorie DOT com


Hello,

I have used pgcc extensively for 2 months. First of all let me say
that pgcc is very, very good. Thanks.

The bug is pinned down as follows,

/* bug.c */
#include <stdio.h>
void a (double x)
{
    printf ("x = %f\n", x);
    if (x == 0.0) printf ("bug: x == 0\n");
    return;
}
int main (int argc, char *argv[]) 
{ 
    a (2.0); 
    return(0); 
}


Using pgcc binaries downloaded from
http://www.goof.com/pcg/binaries-linux.html, I get

% /usr/local/pgcc/bin/gcc -O6 -ffast-math bug.c -o bug; ./bug
x = 2.000000
bug: x == 0


As sanity check I use egcs to compile it,

% rpm -qf /usr/bin/gcc
egcs-1.1.2-24
% /usr/bin/gcc -O6 -ffast-math bug.c -o bug; ./bug
x = 2.000000


Since I get different results using egcs and pgcc on the same machine
using identical flags, it means pgcc has a bug.

I don't know if this bug happens on other machines beside my PII
RedHat 5.2.

For details,

% /usr/local/pgcc/bin/gcc -v --save-temps -O6 -ffast-math bug.c -o bug

Reading specs from /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/spe
cs
gcc version pgcc-2.95.2 19991024 (release)
 /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/cpp -lang-c -v -D__GN
UC__=2 -D__GNUC_MINOR__=95 -D__ELF__ -Dunix -D__i386__ -Dlinux -D__ELF__ -D__uni
x__ -D__i386__ -D__linux__ -D__unix -D__linux -Asystem(posix) -D__OPTIMIZE__ -D_
_FAST_MATH__ -Acpu(i386) -Amachine(i386) -Di386 -D__i386 -D__i386__ -Di686 -Dpen
tiumpro -D__i686 -D__i686__ -D__pentiumpro -D__pentiumpro__ bug.c bug.i
GNU CPP version pgcc-2.95.2 19991024 (release) (i386 Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/include
 /usr/include
End of search list.
The following default directories have been omitted from the search path:
 /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/../../../../include/g
++-3
 /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/../../../../i686-pc-l
inux-gnu/include
End of omitted list.
 /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/cc1 bug.i -mno-ieee-f
p -quiet -dumpbase bug.c -O6 -version -ffast-math -o bug.s
GNU C version pgcc-2.95.2 19991024 (release) (i686-pc-linux-gnu) compiled by GNU
 C version pgcc-2.95.2 19991024 (release).
 as -V -Qy -o bug.o bug.s
GNU assembler version 2.9.1 (i386-redhat-linux), using BFD version 2.9.1.0.24
 /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/collect2 -m elf_i386 
-dynamic-linker /lib/ld-linux.so.2 -o bug /usr/lib/crt1.o /usr/lib/crti.o /usr/l
ocal/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/crtbegin.o -L/usr/local/pgcc
/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2 -L/usr/local/pgcc/lib bug.o -lgcc -lc
 -lgcc /usr/local/pgcc/lib/gcc-lib/i686-pc-linux-gnu/pgcc-2.95.2/crtend.o /usr/l
ib/crtn.o



Best regards,

Li Ju.