Skip to content

Latest commit

 

History

History
55 lines (44 loc) · 2.53 KB

cross_compiling.md

File metadata and controls

55 lines (44 loc) · 2.53 KB
Raw

Cross Compiling Concord

Unlike most Autoconf-based projects, Concord uses normal Makefiles. As such, cross-compilation can be rather daunting at first. Fortunately, once you understand it, you won't have any trouble (unless your compiler malfunctions or is misconfigured).

Step 1: getting a cross compiler

Debian-based Linux distros have cross compilers available in their package repositories. For example, to get an ARM cross compiler suitable for building for an old 32-bit Raspberry Pi, run apt-get install gcc-arm-linux-gnueabihf. Search the Debian package repositories for "gcc" to see other cross compilers available.

If you aren't on Debian, you can use cross-compilers from here, although, do note that these compilers might take a fair bit of work to get working perfectly. If you do use one of these, ensure that $PATH gets updated to include the compiler's bin directory, or you won't be able to invoke the compiler.

Step 2: cross-compiling Concord

For this example, we will assume that your host system is a standard x86_64 PC, and uses the target triplet x86_64-pc-linux-gnu. We will be cross-compiling to a 64-bit Raspberry Pi 4, with the target triplet aarch64-linux-gnu. Now, when GCC cross-compilers are made, all of the built executables for the compiler are prefixed with the target tripet. This means that our actual C compiler command is aarch64-linux-gnu-gcc. This will be our CC value.

The gencodecs system that Concord uses requires that the system C compiler is available. This means we have to set HOSTCC when we compile. Since our target triplet is x86_64-pc-linux-gnu, this means that our host C compiler is named x86_64-pc-linux-gnu-gcc. However, since this is the primary C compiler on the system, we can just use gcc for CC.

Finally, we will install Concord to the Raspberry Pi by directly accessing its root filesystem via NFS. The Pi's Linux image has been mounted read-write into /mnt. Since we want Concord to go into /usr/local, our target PREFIX path for make install is /mnt/usr/local.

Okay, we can now run the commands to actually compile.

cd gencodecs
make HOSTCC=gcc CC=aarch64-linux-gnu-gcc
cd ..
make CC=aarch64-linux-gnu-gcc
make install PREFIX=/mnt/usr/local

Easy as that! Granted, you can perform a compilation with fewer typed commands if you export those three variables beforehand, but, this guide was written with maximum learning in mind (and demonstrating why gencodecs needs the split compilation procedure).