usage of mark_as_superbuild

[KrisThielemans]

I don't think we use this properly.

SuperBuild.cmake should add some variables to all subprojects

Indeed, it tries to do this (could do it for more of them I think). However, it says

mark_as_superbuild(
   PROJECTS ALL_PROJECTS
   VARS CMAKE_GENERATOR:STRING CMAKE_GENERATOR_PLATFORM:STRING CMAKE_GENERATOR_TOOLSET:STRING
        CMAKE_C_COMPILER:FILEPATH CMAKE_CXX_COMPILER:FILEPATH
        CMAKE_INSTALL_PREFIX:PATH
)

I think this has to be

mark_as_superbuild(
   ALL_PROJECTS
 ..
)

No idea why it would work now... but I think it does as I put it in :-)

All the external projects use it to pass CMake variables on

code is

mark_as_superbuild(
    VARS
        ${externalProjName}_DIR:PATH
    LABELS
      "FIND_PACKAGE"
  )

This has 2 problems as far as I can see:

• It is only correct if the project indeeds sets/need the *_DIR variable (many do not, e.g. GTEST_ROOT).
• According to the doc, mark_as_superbuild adds this variable then only to the top-level project, which in our case is CCPPETMR, but not to the projects where they are actually needed.

The 2nd item seems to imply these lines are currently effectively ignored. Hence the need for us to specify all the variables by hand again.

I wonder if we should use ALL_PROJECTS here as well, although then we're going to add variables where we actually don't need/use them. A better way would be to know to which projects we need to add them, but then we introduce dependencies on "downstream" projects, which seems a bad idea.

Probably a better solution is to forget about mark_as_superbuild in the sub-projects, and to introduce a variable with all CMake args that need to be set if someone wants to use this project (but that seems exactly what mark_as_superbuild seems to aim to provide).

Summary

I'm confused...

Here's an old-ish post with some info. It refers to old Slicer stuff, but here's a recent link. Note that this also has some interesting stuff with unset and ExternalProject_SetIfNotDefined which might be relevant to #51.

[KrisThielemans]

Wrong usage in SuperBuild.cmake is/was fixed in #148