diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 4a9ef30bc..b5f7ffb01 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -38,22 +38,30 @@ cmMakefile::cmMakefile()
   // Setup the default include complaint regular expression (match nothing).
   m_ComplainFileRegularExpression = "^$";
   // Source and header file extensions that we can handle
-  m_SourceFileExtensions.push_back( "cxx" );
-  m_SourceFileExtensions.push_back( "cpp" );
-  m_SourceFileExtensions.push_back( "c" );
+  m_SourceFileExtensions.push_back( "C" );
   m_SourceFileExtensions.push_back( "M" );
+  m_SourceFileExtensions.push_back( "c" );
+  m_SourceFileExtensions.push_back( "c++" );
+  m_SourceFileExtensions.push_back( "cc" );
+  m_SourceFileExtensions.push_back( "cpp" );
+  m_SourceFileExtensions.push_back( "cxx" );
   m_SourceFileExtensions.push_back( "m" );
   m_SourceFileExtensions.push_back( "mm" );
 
   m_HeaderFileExtensions.push_back( "h" );
-  m_HeaderFileExtensions.push_back( "txx" );
+  m_HeaderFileExtensions.push_back( "h++" );
+  m_HeaderFileExtensions.push_back( "hm" );
+  m_HeaderFileExtensions.push_back( "hpp" );
+  m_HeaderFileExtensions.push_back( "hxx" );
   m_HeaderFileExtensions.push_back( "in" );
+  m_HeaderFileExtensions.push_back( "txx" );
   
   m_DefineFlags = " ";
   m_LocalGenerator = 0;
   this->AddSourceGroup("", "^.*$");
-  this->AddSourceGroup("Source Files", "\\.(cpp|C|c|cxx|rc|def|r|odl|idl|hpj|bat)$");
-  this->AddSourceGroup("Header Files", "\\.(h|hh|hpp|hxx|hm|inl)$");
+  this->AddSourceGroup("Source Files", 
+                       "\\.(C|M|c|c++|cc|cpp|cxx|m|mm|rc|def|r|odl|idl|hpj|bat)$");
+  this->AddSourceGroup("Header Files", "\\.(h|h++|hm|hpp|hxx|in|txx|inl)$");
   this->AddDefaultDefinitions();
 }
 
diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx
index 0b32313ef..7a5025601 100644
--- a/Source/cmSystemTools.cxx
+++ b/Source/cmSystemTools.cxx
@@ -2286,16 +2286,26 @@ cmSystemTools::FileFormat cmSystemTools::GetFileFormat(const char* cext)
     }
   std::string ext = cmSystemTools::LowerCase(cext);
   if ( ext == "c" || ext == ".c" ) { return cmSystemTools::C_FILE_FORMAT; }
-  if ( ext == "cxx" || ext == ".cxx" ||
-       ext == "cpp" || ext == ".cpp" ||
-       ext == "c++" || ext == ".c++" ||
-       ext == "mm" || ext == ".mm" ||
-       ext == "cc" || ext == ".cc" ) { return cmSystemTools::CXX_FILE_FORMAT; }
+  if ( 
+    ext == "C" || ext == ".C" ||
+    ext == "M" || ext == ".M" ||
+    ext == "c++" || ext == ".c++" ||
+    ext == "cc" || ext == ".cc" ||
+    ext == "cpp" || ext == ".cpp" ||
+    ext == "cxx" || ext == ".cxx" ||
+    ext == "m" || ext == ".m" ||
+    ext == "mm" || ext == ".mm"
+    ) { return cmSystemTools::CXX_FILE_FORMAT; }
   if ( ext == "java" || ext == ".java" ) { return cmSystemTools::JAVA_FILE_FORMAT; }
-  if ( ext == "h" || ext == ".h" || 
-       ext == "hpp" || ext == ".hpp" || 
-       ext == "h++" || ext == ".h++" ||
-       ext == "hxx" || ext == ".hxx" ) { return cmSystemTools::HEADER_FILE_FORMAT; }
+  if ( 
+    ext == "h" || ext == ".h" || 
+    ext == "h++" || ext == ".h++" ||
+    ext == "hm" || ext == ".hm" || 
+    ext == "hpp" || ext == ".hpp" || 
+    ext == "hxx" || ext == ".hxx" ||
+    ext == "in" || ext == ".in" ||
+    ext == "txx" || ext == ".txx"
+    ) { return cmSystemTools::HEADER_FILE_FORMAT; }
   if ( ext == "rc" || ext == ".rc" ) { return cmSystemTools::RESOURCE_FILE_FORMAT; }
   if ( ext == "def" || ext == ".def" ) { return cmSystemTools::DEFINITION_FILE_FORMAT; }
   if ( ext == "lib" || ext == ".lib" ||