From 9349d69abf69795e115329475d56ff0583b6c79c Mon Sep 17 00:00:00 2001
From: Vadim Zhukov <persgray@gmail.com>
Date: Sun, 28 Jul 2013 14:11:51 +0400
Subject: Add cmake_reset_check_state() macro

It's acknowledged that check state should not generally nest,
so it should be cleared when used, for example, in Find* module.

Also, add optional RESET argument to cmake_push_check_state().
---
 Modules/CMakePushCheckState.cmake | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/Modules/CMakePushCheckState.cmake b/Modules/CMakePushCheckState.cmake
index 08809bf..b37b706 100644
--- a/Modules/CMakePushCheckState.cmake
+++ b/Modules/CMakePushCheckState.cmake
@@ -1,8 +1,10 @@
-# This module defines two macros:
+# This module defines three macros:
 # CMAKE_PUSH_CHECK_STATE()
-# and
 # CMAKE_POP_CHECK_STATE()
-# These two macros can be used to save and restore the state of the variables
+# and
+# CMAKE_RESET_CHECK_STATE()
+# These macros can be used to save, restore and reset (i.e., clear contents)
+# the state of the variables
 # CMAKE_REQUIRED_FLAGS, CMAKE_REQUIRED_DEFINITIONS, CMAKE_REQUIRED_LIBRARIES
 # and CMAKE_REQUIRED_INCLUDES used by the various Check-files coming with CMake,
 # like e.g. check_function_exists() etc.
@@ -11,9 +13,16 @@
 # but after the Find-module has been executed they should have the same value
 # as they had before.
 #
+# CMAKE_PUSH_CHECK_STATE() macro receives optional argument RESET. Whether it's specified,
+# CMAKE_PUSH_CHECK_STATE() will set all CMAKE_REQUIRED_* variables to empty values, same
+# as CMAKE_RESET_CHECK_STATE() call will do.
+#
 # Usage:
-#   cmake_push_check_state()
-#   set(CMAKE_REQUIRED_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS} -DSOME_MORE_DEF)
+#   cmake_push_check_state(RESET)
+#   set(CMAKE_REQUIRED_DEFINITIONS -DSOME_MORE_DEF)
+#   check_function_exists(...)
+#   cmake_reset_check_state()
+#   set(CMAKE_REQUIRED_DEFINITIONS -DANOTHER_DEF)
 #   check_function_exists(...)
 #   cmake_pop_check_state()
 
@@ -31,6 +40,15 @@
 #  License text for the above reference.)
 
 
+macro(CMAKE_RESET_CHECK_STATE)
+
+   set(CMAKE_REQUIRED_INCLUDES)
+   set(CMAKE_REQUIRED_DEFINITIONS)
+   set(CMAKE_REQUIRED_LIBRARIES)
+   set(CMAKE_REQUIRED_FLAGS)
+
+endmacro()
+
 macro(CMAKE_PUSH_CHECK_STATE)
 
    if(NOT DEFINED _CMAKE_PUSH_CHECK_STATE_COUNTER)
@@ -43,6 +61,11 @@ macro(CMAKE_PUSH_CHECK_STATE)
    set(_CMAKE_REQUIRED_DEFINITIONS_SAVE_${_CMAKE_PUSH_CHECK_STATE_COUNTER} ${CMAKE_REQUIRED_DEFINITIONS})
    set(_CMAKE_REQUIRED_LIBRARIES_SAVE_${_CMAKE_PUSH_CHECK_STATE_COUNTER}   ${CMAKE_REQUIRED_LIBRARIES})
    set(_CMAKE_REQUIRED_FLAGS_SAVE_${_CMAKE_PUSH_CHECK_STATE_COUNTER}       ${CMAKE_REQUIRED_FLAGS})
+
+   if (ARGC GREATER 0 AND ARGV0 STREQUAL "RESET")
+      cmake_reset_check_state()
+   endif()
+
 endmacro()
 
 macro(CMAKE_POP_CHECK_STATE)
-- 
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