Hello,
This was posted to linux.redhat.devel newsgroup. Looks like a bug, but then
my status as a programmer is beginner. :-)
Regards,
Jim H
,--------------- Forwarded message (begin)
Subject: const array bug in g++?
From: [EMAIL PROTECTED]
Date: Wed, 18 Apr 2001 10:47:52 -0700
Hi,
An early version was posted a couple of days ago to
comp.lang.c++.moderated.
I think I need to enlarge the audience with a little bit new testing
results.
The following simple program
#include <iostream>
using namespace std;
const float C = 0.5F;
const float C1[2] = {0.5F, 0.5F};
const float C2[2][2] = {{C1[0], C1[0]}, {C1[1], C1[1]}};
//const float C2[2][2] = {{C, C}, {C, C}};
int main()
{
cout<<"C1[0] = "<<C1[0]<<endl;
cout<<"C2[0][0] = "<<C2[0][0]<<endl;
return 0;
}
outputs the wrong result when it is compiled with gcc v2.96. I
tried with g++ (gcc version 2.96 20000731 from update file
gcc-2.96-69.i386.rpm) under Red Hat Linux 7.0, as well as the
g++ (gcc version 2.96 20000731 from gcc-2.96-81.i386.rpm) under
the just released RedHat 7.1 (2.96-81), both gave me
the wrong result for C2[0][0] (which should be 0.5):
C1[0] = 0.5
C2[0][0] = 0
If I use the the statement that is commented out above, the
output is right.The program works fine with Microsoft VC++ 6.0,
and also works with old gcc (the autual program was last tested about
1.5 years ago. I think it was compiled with gcc v2.73).
The compiled program links to the following libraries:
libstdc++-libc6.2-2.so.3 => /usr/lib/libstdc++-libc6.2-2.so.3 (0x40027000)
libm.so.6 => /lib/i686/libm.so.6 (0x4006a000)
libc.so.6 => /lib/i686/libc.so.6 (0x4008e000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
under RedHat 7.1, and to
libstdc++-libc6.2-2.so.3 => /usr/lib/libstdc++-libc6.2-2.so.3
(0x40021000)
libm.so.6 => /lib/libm.so.6 (0x40064000)
libc.so.6 => /lib/libc.so.6 (0x40083000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
under RedHat 7.0, if the info helps.
Does anyone can explain why the gcc 2.96 does not output the correct
answer,
or it is simply a bug in this version of gcc (or the libraries)?
Thanks in advance.
Regards,
Bin
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