How to compile GCC 32bit app on 64bit ARM device?

[Gistapo]

Hello,

I have Raspberry Pi 3 Model B with https://github.com/sakaki-/gentoo-on-rpi3-64bit image installed on it.

By default there is gcc-8.2.0-r3 pre-installed already, but I have installed gcc-5.4.0-r4 and selected it as default beacause of my C++ app that I need to compile.

Code: Select all

 gcc-config --list-profiles
 [1] aarch64-unknown-linux-gnu-5.4.0 *
 [2] aarch64-unknown-linux-gnu-8.2.0

The questions is, how to download multilib to be able to compile 32bit app on my 64bit OS ARM device?

Thanks in advance to everyone for suggestions.

[NeddySeagoon]

Moved from Portage & Programming to Gentoo on ARM.

First of all, if your program is C++, it might just build on 64 bit. Try it.

Gentoo does not currently support multilib on arm64.
Arm64 multilib is a bit odd.
On arm64, the 32 bit instruction set is optional. Some CPUs support it, some don't. The Pi does.

[Gistapo]

Moved from Portage & Programming to Gentoo on ARM.

First of all, if your program is C++, it might just build on 64 bit. Try it.

Gentoo does not currently support multilib on arm64.
Arm64 multilib is a bit odd.
On arm64, the 32 bit instruction set is optional. Some CPUs support it, some don't. The Pi does.

Thank you for your answer, now everything is clear.
I did compile 32bit app on 64bit Ubuntu on x86_64 PC device, so I thouth it is also possible to do the same on ARM devices using by downloading gcc-multilib and using gcc -m32 parameter to compile. I did spent a few days trying this, but here is a simple answer it is not available.

Topic can be closed now.

[Hu]

What happens when you compile your program as 64-bit on arm64?

[Gistapo]

What happens when you compile your program as 64-bit on arm64?

It is compiled without any problems as 64-bit on arm64, but I was looking for way to compile 32-bit app, but it is not supported as it is stated above.

[NeddySeagoon]

Gistapo,

There is the 32 bit chroot approach. You need enough in the chroot to support the toolchain and libraries your code links against.

Provided you have kernel support, arm64 CPUs that support 32 bit mode too, switch modes transparently.
As its a Pi, you could have a 32 bit install on another SDCard,

-- Edit --

If you are feeling really adventuerous you have the 32 bit KVM option too. Sakakis image supports KVM.

[Sakaki]

Gistapo,

There is the 32 bit chroot approach. You need enough in the chroot to support the toolchain and libraries your code links against.

Provided you have kernel support, arm64 CPUs that support 32 bit mode too, switch modes transparently.
As its a Pi, you could have a 32 bit install on another SDCard,

There are instructions for doing this on the gentoo-on-rpi3-64bit project's open wiki, here (for 32-bit Raspbian as the chroot guest, but you could easily adapt to run 32-bit Gentoo as the guest instead).

If you are feeling really adventuerous you have the 32 bit KVM option too. Sakakis image supports KVM.

Instructions for this are on the same wiki here and here (this is for 64-bit Ubuntu 18.04 server as the kvm guest, but you can run 32-bit KVM guests with a 64-bit kernel system also).

[Gistapo]

Sakaki,

Thanks for provided info, but it doesn't looks that simple as just installing gcc-multilib and run gcc -m32 on Ubuntu Linux x86_64 architecture machine, so I don't want to waist my time on it anymore.

[Crocodillian]

For anyone coming across this thread, gcc -m32 works just fine in current gentoo.

You just need to add the abi_x86_32 USE flag to any libraries you will link and make sure you are using a multilib profile.

[NeddySeagoon]

Crocodillian,

You need a hardware platform that supports the optional, on arm64, 32 bit instruction set too.

[antonlacon]

For anyone coming across this thread, gcc -m32 works just fine in current gentoo.

You just need to add the abi_x86_32 USE flag to any libraries you will link and make sure you are using a multilib profile.

Your instructions are fine for x86-64, but this is arm. You need a 32-bit arm toolchain to build for arm. -m32 is not a valid flag for aarch64's gcc: http://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html