Basic cross compiling tutorial?

nkoplm · 02-04-2010, 12:00 PM

Hello,

I have written a program that I would like to cross compile for x86 and x86_64 architectures. I have tried google and the search function here to no success, most information I find is too specific (instructions for a specific program), or dealing with cross compiling for windows on linux.

Does anyone know of a tutorial dealing with straight making a 32 bit binary on a 64 bit processor (both are intel)?

ForzaItalia2006 · 02-04-2010, 05:00 PM

Hey,

that what you're talking about is not really cross-compiling, because the x86_64 instruction set is just an extension to the x86 instruction set so that I would assume that most compilers for x86_64 also allow you to compile 32-bit code (at least gcc does by using the -m32 flag).

Cross compiling really means that you build your executable e.g. on Linux/x86, but the application will finally be executed on a PowerPC.

First of all, here's a basic tutorial for gcc on Linux: http://linux.bytesex.org/cross-compiler.html

Generally, you need the following things:

cross compiler, you could build gcc as a cross-compiler for any support platform (for example, --host=<x86>, but --target=<ia64>)
binutils of your target platform (linker, assembler), because you will have to finally link the app on your system
header files of your target system
libraries of your target system, because the linker must be able to access static and shared libraries for linking the application

That's just a basic skeleton, but hopefully it gives you some starting points ...

- Andi -

theNbomr · 02-05-2010, 09:33 AM

First, you need a cross compiler (cross toolchain, to be more accurate) that runs on your build host, and creates object code for the target host. After that, it can be as simple as having your makefile point at the cross compiler when performing the build of your application.
To build a cross toolchain on your build host, you can use a tool such as crosstool-ng.

Code:

theNbomr@myhost:~/junk$ touch helloWorld.c
theNbomr@myhost:~/junk$ make CC=~/x-tools/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-gcc helloWorld
/home/theNbomr/x-tools/arm-unknown-linux-gnueabi/bin/arm-unknown-linux-gnueabi-gcc     helloWorld.c   -o helloWorld
theNbomr@myhost:~/junk$ file helloWorld
helloWorld: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.31, not stripped

This example uses a cross toolchain targeting a ARM processor, just because I had that at hand, and because the resulting object code is more distinct than simply a variant of another x86 CPU target object code.
--- rod