CMake toolchain expressions

Question

I am trying to write a Toolchain file for a custom compiler and I am stuck at the options of the tools. I actually need a variation of the output filename to be added to a parameter in CMAKE_CXX_LINK_EXECUTABLE variable.

I found random examples on the internet on how to include some expressions, like <TARGET> and <OBJECTS> but https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html avoids to explain them properly. What are those? Some look like variables, some like Generator expressions (https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html ) , some like CMake properties.

But where are the valid ones listed? And which string operations can I do with them?

Answer 1

They are placeholders. They don't necessarily correspond to any variable or property. They are specific to rules like CMAKE_<LANG>_LINK_EXECUTABLE.

I couldn't find any documentation about them, but there's some information in the source for CXX rules.

Sources:

• How do CMake placeholders work?
• cmRulePlaceholderExpander::ExpandVariable
• Example of setting up RuleVariables from the source