Where are variables set in cmake?

Question

I'm having trouble with a make process, so after some reading I was led to the CMakeLists.txt file, which as I understand, is a configuration of sorts for cmake (which in turn generated makefiles).

So, I'm looking through a CMakeLists.txt file. I'm seeing references to something called ${PROJECT_SOURCE_DIR} but it doesn't seem to be declared anywhere in the file. Where is it declared?

Answer 1

There are many automatic variables, which are set by CMake or by other means. See variables documentation.