CMake: pass variables to custom toolchain file

I am creating a toolchain file for a gcc-based C compiler for a non-popular platform. I would like users to pass a path to compiler root directory, while a toolchain file will set up all the paths to c/c++/ar/whatever, set proper compile flags.

My toolchain file starts with this check:


All other paths are calculated based on TOOLCHAIN_PREFIX variable, which I want users to be passed as a parameter to cmake (e.g. cmake -DTOOLCHAIN_PREFIX=/path/to/compiler/root ..)

Problem: during configuration process, cmake gets to ‘Detecting C compiler ABI info’ step, and runs compilation of a test program, and passes there a toolchain file. The issue is that my variable TOOLCHAIN_PREFIX is not passed there. As result I get error and configuration process stops.

What is the proper way of passing my TOOLCHAIN_PREFIX parameter to the nested try_compile() operations?

Alternative question: what is the proper way of building toolchain files so that it can search for a compiler at a specific path?


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