Merge topic 'fix-check-module-DEFINED-tests'

4ffec8f6 Check*: Add compatibility hack for old VXL code

Modules/CheckFunctionExists.cmake

@@ -38,7 +38,7 @@
 
 
 macro(CHECK_FUNCTION_EXISTS FUNCTION VARIABLE)
-  if(NOT DEFINED "${VARIABLE}")
+  if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}")
     set(MACRO_CHECK_FUNCTION_DEFINITIONS
       "-DCHECK_FUNCTION_EXISTS=${FUNCTION} ${CMAKE_REQUIRED_FLAGS}")
     if(NOT CMAKE_REQUIRED_QUIET)

Modules/CheckIncludeFileCXX.cmake

@@ -44,7 +44,7 @@
 #  License text for the above reference.)
 
 macro(CHECK_INCLUDE_FILE_CXX INCLUDE VARIABLE)
-  if(NOT DEFINED "${VARIABLE}")
+  if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}")
     if(CMAKE_REQUIRED_INCLUDES)
       set(CHECK_INCLUDE_FILE_CXX_INCLUDE_DIRS "-DINCLUDE_DIRECTORIES=${CMAKE_REQUIRED_INCLUDES}")
     else()

Modules/CheckSymbolExists.cmake

@@ -50,7 +50,7 @@ macro(CHECK_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
 endmacro()
 
 macro(_CHECK_SYMBOL_EXISTS SOURCEFILE SYMBOL FILES VARIABLE)
-  if(NOT DEFINED "${VARIABLE}")
+  if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}")
     set(CMAKE_CONFIGURABLE_FILE_CONTENT "/* */\n")
     set(MACRO_CHECK_SYMBOL_EXISTS_FLAGS ${CMAKE_REQUIRED_FLAGS})
     if(CMAKE_REQUIRED_LIBRARIES)