How to compile 32-bit executable on 64 bit system

Note: I looked through some of the suggested "similar questions" and didn't find anything that looked conclusive. Plus, it seems most of them are 6 years old (from 2014), so I'm hoping for something more up-to-date (and more likely to "just work").

I have a 64 bit Ubuntu system that works fine. I would like to be able to build a 32 bit version of, say, "hello, world". This is mostly an academic pursuit, but it would be convenient to get it working. It would be nice if compiling with "-m32" would "just work", but it doesn't. Worse, my memory is that this used to "just work" (in an older version of 64 bit Linux), but no longer works.

Observe:

$ cat hello.c
#include <stdio.h>
int main() { puts("hello, world"); return 0; }
$ gcc -m32 hello.c
In file included from hello.c:1:0:
/usr/include/stdio.h:27:10: fatal error: bits/libc-header-start.h: No such file or directory #include <bits/libc-header-start.h> ^~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
$

A bit of poking around suggests that installing these packages (see below) might help, so I did:

apt-get install libc6-dev-i386-x32-cross

which installed the following:

The following NEW packages will be installed:
libc6-dev-i386-x32-cross libc6-dev-x32-cross libc6-i386-x32-cross libc6-x32-cross linux-libc-dev-x32-cross

After that, with a little bit of fudging, I was able to get it to compile, but not link. The link phase gives these error msgs:

/usr/bin/ld: cannot find Scrt1.o: No such file or directory
/usr/bin/ld: cannot find crti.o: No such file or directory
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a when searching for -lgcc
/usr/bin/ld: cannot find -lgcc
/usr/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a when searching for -lgcc
/usr/bin/ld: cannot find -lgcc
collect2: error: ld returned 1 exit status

And I can't get any farther than that.

So, any advice will be appreciated.

2 Answers

You have to install correct development packages by

sudo apt-get install build-essential libc6-dev-i386

And then it will work:

$ gcc hello.c -o hello32 -m32
$ file hello32
hello32: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=444fafde1d2281a8af74adc452a8db046df1276e, not stripped

Yup - it turns out all you have to do is install libc6-dev-i386 - then everything works.

Thanks for the tip!

Note: There is a lot of confusing and wrong information on the Internet...