How to compile a 32-bit application using gcc on the 64-bit Linux version

Posted by Vivek Gite [Last updated: December 20, 2006]

I had to compile a 32-bit application using GNU gcc on the 64-bit version Linux.

Luckily gcc man page directed me to -m32 and -m64 option. These options generate code for a 32-bit or 64-bit environments.

=> The 32-bit environment sets int, long and pointer to 32 bits and generates code that runs on any i386 system.

=> The 64-bit environment sets int to 32 bits and long and pointer to 64 bits and generates code for AMD's x86-64 architecture.

You can pass -m64 or -m32 as follows
For 32 bit version:
$ gcc -m32 -o output32 hello.c
For 64 bit version :
$ gcc -m64 -o output64 hello.c

And output is :
$ ./output32
Output:

Long int size is 4 bytes long!

Now let us see 64 bit output:
$ ./output64

Long int size is 8 bytes long!

Sample code - hello.c:

#include <stdio.h>
int main(){
        long z; printf("Long int size is %i bytes long!\n", sizeof(z)); return 0;
}

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Discussion on This Article:

mojo Says: December 20th, 2006 at 12:15 pm
I think
gcc -m32 -o output64 hello.c

should be
!
gcc -m32 -o output32 hello.c

and

$ gcc -m64 -o output64 hello.c

should be

$ gcc -m64 -o output64 hello.c
nixcraft Says: December 20th, 2006 at 12:18 pm
mojo

Thanks for heads up!
beparas Says: June 1st, 2007 at 12:07 pm
its working . thx
vlad Says: May 19th, 2008 at 5:27 pm
I got this error trying to compile with -m32 :S
/usr/include/gnu/stubs.h:7:27: error: gnu/stubs-32.h

Whats wrong?