ENH: only force the use of ansi flags in backwards mode

Modules/CMakeBackwardCompatibilityCXX.cmake

@@ -22,12 +22,14 @@ IF(NOT CMAKE_SKIP_COMPATIBILITY_TESTS)
       ENDIF(CMAKE_CXX_ACCEPTS_FLAGS)
     ENDIF( CMAKE_TRY_ANSI_CXX_FLAGS MATCHES ".+")
   ENDIF(NOT CMAKE_COMPILER_IS_GNUCXX)
-
+  SET(CMAKE_CXX_FLAGS_SAVE ${CMAKE_CXX_FLAGS})
+  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CMAKE_ANSI_CXXFLAGS}")
   INCLUDE(${CMAKE_ROOT}/Modules/TestForANSIStreamHeaders.cmake)
   INCLUDE(${CMAKE_ROOT}/Modules/CheckIncludeFileCXX.cmake)
   INCLUDE(${CMAKE_ROOT}/Modules/TestForSTDNamespace.cmake)
   INCLUDE(${CMAKE_ROOT}/Modules/TestForANSIForScope.cmake)
   CHECK_INCLUDE_FILE_CXX("sstream" CMAKE_HAS_ANSI_STRING_STREAM)
+  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS_SAVE}")
   IF(NOT CMAKE_HAS_ANSI_STRING_STREAM)
     SET(  CMAKE_NO_ANSI_STRING_STREAM 1 CACHE INTERNAL 
          "Does the compiler support sstream or stringstream.")

Modules/CheckIncludeFileCXX.cmake

@@ -15,7 +15,6 @@ MACRO(CHECK_INCLUDE_FILE_CXX INCLUDE VARIABLE)
     TRY_COMPILE(${VARIABLE}
                ${CMAKE_BINARY_DIR}
                ${CMAKE_BINARY_DIR}/CMakeTmp/CheckIncludeFile.cxx
-               CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${CMAKE_ANSI_CXXFLAGS}
                OUTPUT_VARIABLE OUTPUT)
     IF(${VARIABLE})
       MESSAGE(STATUS "Checking for CXX include file ${INCLUDE} -- found")

Modules/TestForANSIForScope.cmake

@@ -7,8 +7,7 @@
 IF(NOT CMAKE_ANSI_FOR_SCOPE)
   MESSAGE(STATUS "Check for ANSI scope")
   TRY_COMPILE(CMAKE_ANSI_FOR_SCOPE  ${CMAKE_BINARY_DIR} 
-    ${CMAKE_ROOT}/Modules/TestForAnsiForScope.cxx
-    CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${CMAKE_ANSI_CXXFLAGS})
+    ${CMAKE_ROOT}/Modules/TestForAnsiForScope.cxx)
   IF (CMAKE_ANSI_FOR_SCOPE)
     MESSAGE(STATUS "Check for ANSI scope - found")
     SET (CMAKE_NO_ANSI_FOR_SCOPE 0 CACHE INTERNAL 

Modules/TestForSTDNamespace.cmake

@@ -7,8 +7,7 @@
 IF(NOT CMAKE_STD_NAMESPACE)
   MESSAGE(STATUS "Check for STD namespace")
   TRY_COMPILE(CMAKE_STD_NAMESPACE  ${CMAKE_BINARY_DIR} 
-    ${CMAKE_ROOT}/Modules/TestForSTDNamespace.cxx
-    CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${CMAKE_ANSI_CXXFLAGS})
+    ${CMAKE_ROOT}/Modules/TestForSTDNamespace.cxx)
   IF (CMAKE_STD_NAMESPACE)
     MESSAGE(STATUS "Check for STD namespace - found")
     SET (CMAKE_NO_STD_NAMESPACE 0 CACHE INTERNAL 

Source/cmTryCompileCommand.cxx

@@ -152,10 +152,25 @@ int cmTryCompileCommand::CoreTryCompileCode(
                            "; TRY_COMPILE only works for C and CXX files");
       return -1;
       }
-
+    const char* cflags = mf->GetDefinition("CMAKE_C_FLAGS"); 
     fprintf(fout, "SET(CMAKE_VERBOSE_MAKEFILE 1)\n");
-    fprintf(fout, "SET(CMAKE_C_FLAGS \"${CMAKE_C_FLAGS} ${COMPILE_DEFINITIONS}\")\n");
-    fprintf(fout, "SET(CMAKE_CXX_FLAGS \"${CMAKE_CXX_FLAGS} ${COMPILE_DEFINITIONS}\")\n");
+    fprintf(fout, "SET(CMAKE_C_FLAGS \"${CMAKE_C_FLAGS}");
+    if(cflags)
+      {
+      fprintf(fout, " %s ", cflags);
+      }
+    fprintf(fout, " ${COMPILE_DEFINITIONS}\")\n");
+    // CXX specific flags
+    if(format == cmSystemTools::CXX_FILE_FORMAT )
+      {
+      const char* cxxflags = mf->GetDefinition("CMAKE_CXX_FLAGS");
+      fprintf(fout, "SET(CMAKE_CXX_FLAGS \"${CMAKE_CXX_FLAGS} ");
+      if(cxxflags)
+        {
+        fprintf(fout, " %s ", cxxflags);
+        }
+      fprintf(fout, " ${COMPILE_DEFINITIONS}\")\n");
+      }
     fprintf(fout, "INCLUDE_DIRECTORIES(${INCLUDE_DIRECTORIES})\n");
     fprintf(fout, "LINK_DIRECTORIES(${LINK_DIRECTORIES})\n");
     // handle any compile flags we need to pass on