How to specify the compiler for CMAKE external project?

Question

I am including an external project with ExternalProject_Add. What I want is to be able to do

cmake -DCMAKE_CXX_COMPILER=<some compiler> <assume correct path>

for the top-level project so that my chosen compiler propagates to the externally included projects. I expect something that I can put in the ExternalProject_Add command:

ExternalProject_Add (

  some_external_project

  PREFIX ...            # Assume this works.
  GIT_REPOSITORY ...    # Assume this works too.

  # What should I write here to tell it to use the ${CMAKE_CXX_COMPILER}
  # of the top-level project ?
)

Answer 1

The following worked for me in the top-level project:

ExternalProject_Add (

  some_external_project

  PREFIX ...          # Assume this works.
  GIT_REPOSITORY ...  # Assume this works too.

  # This did the trick for me.
  CMAKE_ARGS -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
)