Compiling 32bit C++ on 64bit Linux

linuxmthomson · 06-10-2008, 07:03 PM

Hi all,

I am running Linux Red Hat 5 64bit OS and I am trying to work out how to compile 32 bit c++ apps on this 64 bit OS.

I have a simple helloworld app that compiles and runs with default compilation :

g++ test.cpp -> produces a.out that runs without issue

Now I am trying to get it to build in 32bit mode using -m32
and I get the following error:

g++ -m32 test.cpp
In file included from /usr/include/features.h:352,
from /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/x86_64-redhat-linux/bits/os_defines.h:39,
from /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/x86_64-redhat-linux/bits/c++config.h:39,
from /usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/iostream:43,
from test.cpp:1:
/usr/include/gnu/stubs.h:7:27: error: gnu/stubs-32.h: No such file or directory

I think it may be a problem because it looks like there may be no 32 bit C++ libs / headers installed

The only directory under /usr/lib/gcc is x86_64-redhat-linux

Any help would be greatly appreciated!

student04 · 06-11-2008, 06:46 AM

I know for a fact that various operating systems (not just talking about linux ones) have either only support for the 64-bit environment, support both 64/32-bit, or for 32-bit only. Ubuntu, to my latest knowledge, has a 64-bit version but which cannot run 32-bit binaries. Gentoo's 64-bit versions indeed have support for the 32-bit libraries (my install has /usr/lib32 and /usr/lib64 for each group).

I just compiled and ran this file on my gentoo box:

Code:

[alex@suicide temp]$ gcc --version
gcc (GCC) 4.1.2 (Gentoo 4.1.2 p1.1)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[alex@computer temp]$ cat test.c
#include <stdio.h>
int main() {
        printf( "works\n" );
}
[alex@computer temp]$ gcc test.c -o test64
[alex@computer temp]$ gcc -m32 test.c -o test32
[alex@computer temp]$ file test64
test64: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), not stripped
[alex@computer temp]$ file test32
test32: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), not stripped
[alex@computer temp]$ ./test64
works
[alex@computer temp]$ ./test32
works

Try to see if you can do this with a simple C file like I did (they use fewer headers). If that doesn't work, I'd look to see if you can install packages from the repository that are the 32-bit libraries.

Oh, and welcome to LQ!

paulsm4 · 06-11-2008, 05:46 PM

Hi, Linuxmthomson -

You're absolutely on the right track:

a) You've got G++ installed, and confirmed that it can successfully build 64-bit .exe's

b) You know about, and tried, "-m32" to try building a 32-bit .exe.

So far, so good. I think you'll be home free if you just installed the 32-bit dev tools (along with the 64-bit tools you've already got):

Quote:

EXAMPLE:
sudo apt-get install libc6-dev-i386

You should be able to install and use both the 32- and 64-bit dev tools - just make sure they're both the *same* version of GCC.

'Hope that helps .. PSM

linuxmthomson · 06-11-2008, 06:05 PM

Thanks guys.

Yes, using Yum I managed to update most of the dependant libs ( using a generic yum update ) then ran a :

yum install glibc-devel

and that installed the correct lib.

I can now compile both 32 and 64 bit apps.

Thanks for your help