[CMake] Testing for a target broke for me

[Williams, Norman K]

On 12/12/13 2:13 PM, "Richard Shaw" <hobbes1069 at gmail.com<mailto:hobbes1069 at gmail.com>> wrote:

Very interesting but not quite what I'm looking for, in this case the main CMakeLists.txt does actually build a project, I just need it to build wxWidgets first.

Well it's up to you but 'build X and then build Y' is the definition of how using ExternalProject work.

What you describe doesn't seem like it would ever work, because the CMake source code is evaluated at Configuration time, not compile time.  How is wxWidgets a target? Do you have an ADD_CUSTOM_TARGET command somewhere? You might have had it accidentally work because of how variables persist between make/configure runs in CMakeCache.txt, but I don't see how it could ever be dependable or predictable.

if(BOOTSTRAP_WXWIDGETS AND NOT TARGET wxWidgets)
message("Build wxWidgets")
else()
message("Doing normal build")
endif()

The CMake code below would do what you want to do. It builds wxWindows, and then builds your project.

project(TWOSTAGE)
include(ExternalProject)
if(NOT BUILD_MY_PROJECT) # starts out un-set/false at top level build dir
  include(cmake/BuildWxWidgets.cmake)
  # your project builds in a subdirectory of the top level build dir
  ExternalProject_add(MyActualProject
DOWNLOAD_COMMAND ""
        SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}
        BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/MyActualProject-build
        CMAKE_ARGS
-DBUILD_MY_PROJECT:BOOL=TRUE
        <all relevant cmake args, including where to find wxWindows libs/include>
        INSTALL_COMMAND "" # presumably you don't want to install immediately.
  )
else()
  <normal build stuff, depending on WxWidgets>
endif()



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