diff --git a/Modules/Platform/HP-UX.cmake b/Modules/Platform/HP-UX.cmake
index ebc370a84..14f22b3a6 100644
--- a/Modules/Platform/HP-UX.cmake
+++ b/Modules/Platform/HP-UX.cmake
@@ -41,11 +41,12 @@ ELSE(CMAKE_COMPILER_IS_GNUCXX)
   SET(CMAKE_SHARED_LIBRARY_RUNTIME_CXX_FLAG "-Wl,+b")       # -rpath
   SET(CMAKE_SHARED_LIBRARY_CXX_FLAGS "-fPIC")     # -pic 
 
-  SET (CMAKE_CXX_FLAGS "")
-  SET (CMAKE_CXX_FLAGS_DEBUG "-g")
-  SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
-  SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
-  SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-g")
-  SET (CMAKE_C_FLAGS "")
-
+  IF(NOT CMAKE_CXX_FLAGS)
+    SET (CMAKE_CXX_FLAGS "")
+    SET (CMAKE_CXX_FLAGS_DEBUG "-g")
+    SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
+    SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
+    SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-g")
+    SET (CMAKE_C_FLAGS "")
+  ENDIF(NOT CMAKE_CXX_FLAGS)
 ENDIF(CMAKE_COMPILER_IS_GNUCXX)
diff --git a/Modules/Platform/IRIX.cmake b/Modules/Platform/IRIX.cmake
index 8c720ab7c..9117a740a 100644
--- a/Modules/Platform/IRIX.cmake
+++ b/Modules/Platform/IRIX.cmake
@@ -6,12 +6,14 @@ SET(CMAKE_SHARED_LIBRARY_RUNTIME_FLAG_SEP "")   # : or empty
 IF(NOT CMAKE_COMPILER_IS_GNUCXX)
   SET(CMAKE_CXX_CREATE_STATIC_LIBRARY
       "<CMAKE_CXX_COMPILER> -ar -o <TARGET> <OBJECTS>")
-  SET (CMAKE_CXX_FLAGS "")
-  SET (CMAKE_CXX_FLAGS_DEBUG "-g")
-  SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
-  SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
-  SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2")
-  SET (CMAKE_C_FLAGS "")
+  IF(NOT CMAKE_CXX_FLAGS)
+    SET (CMAKE_CXX_FLAGS "")
+    SET (CMAKE_CXX_FLAGS_DEBUG "-g")
+    SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
+    SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
+    SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2")
+    SET (CMAKE_C_FLAGS "")
+  ENDIF(NOT CMAKE_CXX_FLAGS)
 ELSE(NOT CMAKE_COMPILER_IS_GNUCXX)
   INCLUDE(${CMAKE_ROOT}/Modules/Platform/gcc.cmake)
 ENDIF(NOT CMAKE_COMPILER_IS_GNUCXX)
diff --git a/Modules/Platform/IRIX64.cmake b/Modules/Platform/IRIX64.cmake
index eed0e2a28..32654ae4f 100644
--- a/Modules/Platform/IRIX64.cmake
+++ b/Modules/Platform/IRIX64.cmake
@@ -7,12 +7,14 @@ IF(NOT CMAKE_COMPILER_IS_GNUCXX)
   SET(CMAKE_CXX_CREATE_STATIC_LIBRARY
       "<CMAKE_CXX_COMPILER> -ar -o <TARGET> <OBJECTS>")
   SET(CMAKE_ANSI_CXXFLAGS -LANG:std)
-  SET (CMAKE_CXX_FLAGS "")
-  SET (CMAKE_CXX_FLAGS_DEBUG "-g")
-  SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
-  SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
-  SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2")
-  SET (CMAKE_C_FLAGS "")
+  IF(NOT CMAKE_CXX_FLAGS)
+    SET (CMAKE_CXX_FLAGS "")
+    SET (CMAKE_CXX_FLAGS_DEBUG "-g")
+    SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
+    SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
+    SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2")
+    SET (CMAKE_C_FLAGS "")
+  ENDIF(NOT CMAKE_CXX_FLAGS)
 ELSE(NOT CMAKE_COMPILER_IS_GNUCXX)
   INCLUDE(${CMAKE_ROOT}/Modules/Platform/gcc.cmake)
 ENDIF(NOT CMAKE_COMPILER_IS_GNUCXX)
diff --git a/Modules/Platform/Windows-bcc32.cmake b/Modules/Platform/Windows-bcc32.cmake
index 4b2028f80..aacbec5c2 100644
--- a/Modules/Platform/Windows-bcc32.cmake
+++ b/Modules/Platform/Windows-bcc32.cmake
@@ -49,12 +49,15 @@ SET(CMAKE_CREATE_WIN32_EXE -tW -tWM )
 # extra flags for a console app
 SET(CMAKE_CREATE_CONSOLE_EXE -tWC )
 
-SET (CMAKE_CXX_FLAGS "-w- -whid -waus -wpar -tWM -P")
-SET (CMAKE_CXX_FLAGS_DEBUG "-Od -v")
-SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O1")
-SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
-SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-Od")
-SET (CMAKE_C_FLAGS "-w- -whid -waus -tWM")
+IF(NOT CMAKE_CXX_FLAGS)
+  SET (CMAKE_CXX_FLAGS "-w- -whid -waus -wpar -tWM -P")
+  SET (CMAKE_CXX_FLAGS_DEBUG "-Od -v")
+  SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O1")
+  SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
+  SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-Od")
+  SET (CMAKE_C_FLAGS "-w- -whid -waus -tWM")
+ENDIF(NOT CMAKE_CXX_FLAGS)
+
 
 SET (CMAKE_STANDARD_LIBRARIES "import32.lib" CACHE STRING 
      "Libraries linked by defalut with all applications.")
diff --git a/Modules/Platform/Windows-cl.cmake b/Modules/Platform/Windows-cl.cmake
index 0881bf485..ea33cb541 100644
--- a/Modules/Platform/Windows-cl.cmake
+++ b/Modules/Platform/Windows-cl.cmake
@@ -42,12 +42,15 @@ SET (CMAKE_BUILD_TYPE Debug CACHE STRING
 
 SET(CMAKE_CREATE_WIN32_EXE /subsystem:windows)
 
-SET (CMAKE_CXX_FLAGS "/nologo /W3 /Zm1000 /GX /GR")
-SET (CMAKE_CXX_FLAGS_DEBUG "/MDd /Zi /Od /GZ")
-SET (CMAKE_CXX_FLAGS_MINSIZEREL "/MD /O1")
-SET (CMAKE_CXX_FLAGS_RELEASE "/MD /O2")
-SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "/MD /Zi /O2")
-SET (CMAKE_C_FLAGS "/nologo /W3 /Zm1000")
+IF(NOT CMAKE_CXX_FLAGS)
+  SET (CMAKE_CXX_FLAGS "/nologo /W3 /Zm1000 /GX /GR")
+  SET (CMAKE_CXX_FLAGS_DEBUG "/MDd /Zi /Od /GZ")
+  SET (CMAKE_CXX_FLAGS_MINSIZEREL "/MD /O1")
+  SET (CMAKE_CXX_FLAGS_RELEASE "/MD /O2")
+  SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "/MD /Zi /O2")
+  SET (CMAKE_C_FLAGS "/nologo /W3 /Zm1000")
+ENDIF(NOT CMAKE_CXX_FLAGS)
+
 
 SET (CMAKE_STANDARD_LIBRARIES "kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib  kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib" CACHE STRING 
      "Libraries linked by defalut with all applications.")
diff --git a/Modules/Platform/gcc.cmake b/Modules/Platform/gcc.cmake
index 62b3c2e37..54ad33a10 100644
--- a/Modules/Platform/gcc.cmake
+++ b/Modules/Platform/gcc.cmake
@@ -1,6 +1,8 @@
-SET (CMAKE_CXX_FLAGS "")
-SET (CMAKE_CXX_FLAGS_DEBUG "-g")
-SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
-SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
-SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -g")
-SET (CMAKE_C_FLAGS "")
+IF(NOT CMAKE_CXX_FLAGS)
+  SET (CMAKE_CXX_FLAGS "")
+  SET (CMAKE_CXX_FLAGS_DEBUG "-g")
+  SET (CMAKE_CXX_FLAGS_MINSIZEREL "-O3")
+  SET (CMAKE_CXX_FLAGS_RELEASE "-O2")
+  SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -g")
+  SET (CMAKE_C_FLAGS "")
+ENDIF(NOT CMAKE_CXX_FLAGS)