From 4ffec8f666b996aedd592e6d26286cef2cb38b50 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Mon, 18 Aug 2014 10:49:30 -0400
Subject: [PATCH] Check*: Add compatibility hack for old VXL code

The cleanup in commit 4f2fcce4 (Check*: Allow result variables to
contain regex special characters, 2014-07-31) broke old VXL code that
abuses the old "if(MATCHES)" implementation by using

  SET( ${VARIABLE} ${VARIABLE} )

to reset a check result variable.  Add a compatibility hack to the
CheckFunctionExists, CheckIncludeFileCXX, and CheckSymbolExists modules
to re-run their checks when the result variable is set to its own name.
Use STREQUAL instead of MATCHES so that special characters still work.
---
 Modules/CheckFunctionExists.cmake | 2 +-
 Modules/CheckIncludeFileCXX.cmake | 2 +-
 Modules/CheckSymbolExists.cmake   | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Modules/CheckFunctionExists.cmake b/Modules/CheckFunctionExists.cmake
index 01a652b62..4c4334ff8 100644
--- a/Modules/CheckFunctionExists.cmake
+++ b/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)
diff --git a/Modules/CheckIncludeFileCXX.cmake b/Modules/CheckIncludeFileCXX.cmake
index 718e667f4..eff982cc1 100644
--- a/Modules/CheckIncludeFileCXX.cmake
+++ b/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()
diff --git a/Modules/CheckSymbolExists.cmake b/Modules/CheckSymbolExists.cmake
index 6f50c88f4..c31f6b6e3 100644
--- a/Modules/CheckSymbolExists.cmake
+++ b/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)