[SOLVED] CMP0002 error when compiling different subproject with same target

CMP0002 error when compiling different subproject with same target

I've many sub-folders

home
|
|-library1
|-library2
|
|-libraryn

Every subfolder contains a complete library that can compile by itself (every library has a different mantainer). Until now it works correctly and I compile them using a script.

Now I need to create another library, that depends on existing one. In order to do so, I've created a CMakeLists.txt under home folder, using add_subdirectory command that allows me to compile all libraries.

I've something like

cmake_minimum_required (VERSION 2.8)

add_subdirectory(library1)
add_subdirectory(library2)
...
add_subdirectory(libraryn)

When I try to execute cmake I obtain following error for various libraries:

CMake Error at libraryY/CMakeLists.txt:63 (add_custom_target):
  add_custom_target cannot create target "doc" because another target with
  the same name already exists.  The existing target is a custom target
  created in source directory
  "/path/to/libraryX".  See
  documentation for policy CMP0002 for more details.

This happens because in every library we create a doc target in order to compile the Doxygen documentation of the library itself. It works fine when libraryes are compiled one by one, but with the master CMakeLists.txt it seems that I cannot do it.

# Create doc target for doxygen documentation compilation.
find_package (Doxygen)
if (DOXYGEN_FOUND)
  set (Doxygen_Dir ${CMAKE_BINARY_DIR}/export/${Library_Version}/doc)
  # Copy images folder
  file (GLOB IMAGES_SRC "images/*")
  file (COPY ${IMAGES_SRC} DESTINATION ${CMAKE_CURRENT_BINARY_DIR}/images)
  configure_file (${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile @ONLY)
  add_custom_target (doc
    ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile
    WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
    COMMENT "Generating doxygen documentation" VERBATIM
  )
else (DOXYGEN_FOUND)
  message (STATUS "Doxygen must be installed in order to compile doc")
endif (DOXYGEN_FOUND)

Is there a way to compile these project at once without modify this target?

Solution

If you don't want to modify anything so you can build all this projects as subprojects, then you can use ExternalProject_Add to build and install dependencies.

option

Alternatively you can use option command to exclude doc target from build:

# Foo/CMakeLists.txt
option(FOO_BUILD_DOCS "Build doc target for Foo project" OFF)
# ...
if(DOXYGEN_FOUND AND FOO_BUILD_DOCS)
  add_custom_target(doc ...)
endif()

# Boo/CMakeLists.txt
option(BOO_BUILD_DOCS "Build doc target for Boo project" OFF)
# ...
if(DOXYGEN_FOUND AND BOO_BUILD_DOCS)
  add_custom_target(doc ...)
endif()