Compiling for amd64 under i386 Debian

Question

Cheers,

I want to avoid problems with compiling my code on amd64, yet I don't have a 64-bit CPU available and have no hopes of getting upgrade to my machine any time soon. I have no dreams of testing the code (although that should theoretically be possible using qemu-system) but I'd like to at least compile the code using gcc -m64.

Basic idea works:

CFLAGS=-m64 CXXFLAGS=-m64 ./configure --host x86_64-debian-linux

However, the code depends on some libraries which I typically install from Debian packages, such as libsdl1.2-dev, libgmp3-dev and such. Obviously, getting 64-bit versions of packages installed alongside of 32-bit versions is not a one-liner.

What would be your practices for installing the 64-bit packages? Where would you put them, how would you get them there and how would you use them?

To repeat, I don't have 64-bit CPU and cannot afford getting a new machine.

I have already set up amd64-libs-dev to give some basic push to gcc's -m64.

Attempted so far:

• Setting up a 64-bit chroot jail with debootstrap in order to simplify installation of 64-bit development packages for libraries. Failed since finishing the setup (and installing anything afterwards!) requires 64-bit CPU.
• Installing gcc-multilib and g++-multilib. This appears to do nothing beside depending on libc6-dev-amd64 which I already installed through amd64-libs-dev.

Answer 1

check out this fine article that describes how to easily create a 32bit chroot, where you can install all the 32bit tools (gcc and libs)

Answer 2

Doesn't Debian distinguish between lib32 and lib64 directories? In that case, you can just grab the packages and force them to install, regardless of architecture.

If that does not work (or would hose your system!) I would set up a chroot environment and apt-get the 64-bit libraries into there.

Answer 3

You want to look into the dchroot package to set up a simple chroot(8) environment -- that way you can compile real amd64 binaries in a real 64-bit setting with proper libraries and dependencies. This surely works the other way (i.e. I am using i386 chroots on amd64 hosts) but I don't see why it shouldn't work the other way if your cpu supports amd64.

Edit: Now that you stress that you do not have a amd64-capable cpu, it gets a little trickier. "In theory" you could just rebuild gcc from source as a cross-compiler. In practice, that may be too much work. Maybe you can just get another headless box for a few dollars and install amd64 on that?

Answer 4

If you're using debian, before you can use gcc -m64, you need to install gcc-multilib and g++-multilib. This will also install all files needed to link and create a 64bit binary.

You don't have to have a 64bit capable CPU for this either.

Then you can call GCC as follows:

$ gcc -m64 source.c -o source

As for external libraries, debian takes care of that if you have multilib installed. I have a 32bit machine that compiles 64bit code for another machine and links a handful of libraries (libpng, libz for example). Works great and the executable run (debian to debian).

Answer 5

Check out pbuilder, It can create build environments for many architectures, some instructions here