What does “$<$:Release>” mean in cmake?

Question

In buildem_cmake_recipe.cmake, I saw an expression:

    externalproject_add_step(${_name} BuildOtherConfig
                        COMMAND ${CMAKE_COMMAND} --bui         


        

Answer 1

Expressions like $<...> are generator exressions, introduced in CMake 2.8. The main feature of these expressions is that they are evaluated at build time, not at configuration time, like normal CMake variables.

Your particular expression

$<$:Release>

expands to "Release" if Debug configuration is in use.