[CMake] How to build and link Externa Project with exported target

[Michael Wild]

Say your project is called foo, you could do something like this:

# Mark variables to be included in the cache-init script
# The variables must already exist in the cache.
function(foo_add_cache_init_vars)
  get_property(is_defined GLOBAL PROPERTY FOO_CACHE_INIT_VARIABLES DEFINED)
  if(NOT is_defined)
    define_property(GLOBAL PROPERTY FOO_CACHE_INIT_VARIABLES
      BRIEF_DOCS "Variables to be written to the cache initialization script"
      FULL_DOCS "The variables will be used to initialize external projects"
      )
   endif()
   set_property(GLOBAL APPEND PROPERTY FOO_CACHE_INIT_VARIABLES ${ARGN})
endif()

# Write the cache initializer script
function(foo_write_cache_init_script outfile)
  get_property(is_set GLOBAL PROPERTY FOO_CACHE_INIT_VARIABLES SET)
  if(NOT is_set)
    message(FATAL_ERROR
      "You must call foo_add_cache_init_var before calling this function")
  endif()
  get_property(varnames GLOBAL PROPERTY FOO_CACHE_INIT_VARIABLES)
  set(text "# Automatically generated, do not edit!\n")
  foreach(var IN LISTS varnames)
    get_property(vartype CACHE ${var} PROPERTY TYPE)
    get_property(varhelp CACHE ${var} PROPERTY HELPSTRING)
    set(text "${text}set(${var} \"${${var}}\" CACHE ${vartype} \"${varhelp}\")\n")
  endforeach()
  file(WRITE "${outfile}" "${text}")
endfunction()

# here goes the real stuff

foo_add_cache_init_vars(
  CMAKE_C_COMPILER
  CMAKE_CXX_COMPILER
  CMAKE_OSX_ARCHITECTURES
  CMAKE_OSX_DEPLOYMENT_TARGET
  CMAKE_OSX_SYSROOT
  CMAKE_VERBOSE_MAKEFILE
  # ...
  )
foreach(config "" _DEBUG _RELEASE _MINSIZEREL _RELWITHDEBINFO)
  foo_add_cache_init_vars(
    CMAKE_C_FLAGS${config}
    CMAKE_CXX_FLAGS${config}
    CMAKE_MODULE_LINKER_FLAGS${config}
    CMAKE_SHARED_LINKER_FLAGS${config}
    # ...
    )
endforeach()

foo_write_cache_init_script("${CMAKE_BINARY_DIR}/ExternalCacheInitScript.cmake")


I haven't tested it, but something along these lines should work.

HTH

Michael

On 19. Mar, 2010, at 15:11 , Nicola Brisotto wrote:

> Hi,
> the solution with a master CMakeLists.txt works well but now I don't
> know how to write wrapper for OPTION and SET functions, can you give
> me an example?
> I'm quite new to cmake so another question is:
> what is the diffence between create a xxx-config and the file I create
> with INSTALL(EXPORT QXmppClient DESTINATION include/QXmppClient ) ?
> They seem to do the same thing but probably I'm missing something....
> 
> Nicola Brisotto
> 
> 
> 
> On Wed, Mar 17, 2010 at 8:44 PM, Alexander Neundorf
> <a.neundorf-work at gmx.net> wrote:
>> On Wednesday 17 March 2010, Michael Wild wrote:
>>> On 17. Mar, 2010, at 15:43 , Luigi Calori wrote:
>> ...
>>>> Is this ExternalProject_Add feature really used/developed?   I find it
>>>> really nice but a little scared of weather it will be really supported
>>>> and improved. I have done some patching on it but not know if there is a
>>>> group of user/developer eventually interested to submit mods to
>>> 
>>> It is actively used and developed, but also relatively new. If you have
>>> improvements, it's best to create a tracker item with a patch and
>>> description there and post the link to the item on this list.
>> 
>> Yes. And git support for it would be a really nice thing to have :-)
>> 
>> Alex
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