project: Add optional LANGUAGES keyword

Teach the project() command to recognize an optional "LANGUAGES"
keyword after the project name and prior to the list of languages.
Do not allow multiple copies of the keyword.  If the keyword is
specified and no languages are listed, imply NONE.

1 files changed, 21 insertions, 3 deletions

diff --git a/Source/cmProjectCommand.cxx b/Source/cmProjectCommand.cxx
index 11f9a76213..1dcb72be8d 100644
--- a/Source/cmProjectCommand.cxx
+++ b/Source/cmProjectCommand.cxx
@@ -62,15 +62,33 @@ bool cmProjectCommand
        "Value Computed by CMake", cmCacheManager::STATIC);
     }
 
+  bool haveLanguages = false;
   std::vector<std::string> languages;
-  if(args.size() > 1)
+  for(size_t i = 1; i < args.size(); ++i)
     {
-    for(size_t i =1; i < args.size(); ++i)
+    if(args[i] == "LANGUAGES")
+      {
+      if(haveLanguages)
+        {
+        this->Makefile->IssueMessage
+          (cmake::FATAL_ERROR, "LANGUAGES may be specified at most once.");
+        cmSystemTools::SetFatalErrorOccured();
+        return true;
+        }
+      haveLanguages = true;
+      }
+    else
       {
       languages.push_back(args[i]);
       }
     }
-  else
+
+  if (haveLanguages && languages.empty())
+    {
+    languages.push_back("NONE");
+    }
+
+  if (languages.empty())
     {
     // if no language is specified do c and c++
     languages.push_back("C");