规范模块目录和第三方依赖结构

third_party/eigen3/cmake/language_support.cmake

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+# cmake/modules/language_support.cmake
+#
+# Temporary additional general language support is contained within this
+# file.  
+
+# This additional function definition is needed to provide a workaround for
+# CMake bug 9220.
+
+# On debian testing (cmake 2.6.2), I get return code zero when calling 
+# cmake the first time, but cmake crashes when running a second time
+# as follows:
+#
+#  -- The Fortran compiler identification is unknown
+#  CMake Error at /usr/share/cmake-2.6/Modules/CMakeFortranInformation.cmake:7 (GET_FILENAME_COMPONENT):
+#    get_filename_component called with incorrect number of arguments
+#  Call Stack (most recent call first):
+#    CMakeLists.txt:3 (enable_language)
+#
+# My workaround is to invoke cmake twice.  If both return codes are zero, 
+# it is safe to invoke ENABLE_LANGUAGE(Fortran OPTIONAL)
+
+function(workaround_9220 language language_works)
+  #message("DEBUG: language = ${language}")
+  set(text
+    "project(test NONE)
+    cmake_minimum_required(VERSION 2.8.0)
+    set (CMAKE_Fortran_FLAGS \"${CMAKE_Fortran_FLAGS}\")
+    set (CMAKE_EXE_LINKER_FLAGS \"${CMAKE_EXE_LINKER_FLAGS}\")
+    enable_language(${language})
+  ")
+  file(REMOVE_RECURSE ${CMAKE_BINARY_DIR}/language_tests/${language})
+  file(MAKE_DIRECTORY ${CMAKE_BINARY_DIR}/language_tests/${language})
+  file(WRITE ${CMAKE_BINARY_DIR}/language_tests/${language}/CMakeLists.txt
+    ${text})
+  execute_process(
+    COMMAND ${CMAKE_COMMAND} . -G "${CMAKE_GENERATOR}"
+    WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/language_tests/${language}
+    RESULT_VARIABLE return_code
+    OUTPUT_QUIET
+    ERROR_QUIET
+    )
+
+  if(return_code EQUAL 0)
+    # Second run
+    execute_process (
+      COMMAND ${CMAKE_COMMAND} . -G "${CMAKE_GENERATOR}"
+      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/language_tests/${language}
+      RESULT_VARIABLE return_code
+      OUTPUT_QUIET
+      ERROR_QUIET
+      )
+    if(return_code EQUAL 0)
+      set(${language_works} ON PARENT_SCOPE)
+    else(return_code EQUAL 0)
+      set(${language_works} OFF PARENT_SCOPE)
+    endif(return_code EQUAL 0)
+  else(return_code EQUAL 0)
+    set(${language_works} OFF PARENT_SCOPE)
+  endif(return_code EQUAL 0)
+endfunction(workaround_9220)
+
+# Temporary tests of the above function.
+#workaround_9220(CXX CXX_language_works)
+#message("CXX_language_works = ${CXX_language_works}")
+#workaround_9220(CXXp CXXp_language_works)
+#message("CXXp_language_works = ${CXXp_language_works}")
+