BUG: Fix matching of ambiguous sf extensions.

A name with an ambiguous extension may only match an unambiguous name
that is extended by one of the fixed set of extensions tried when
finding the source file on disk.  This rule makes matching of source
files with ambiguous extensions much less aggressive but still
sufficient.

Source/cmSourceFileLocation.cxx

@@ -151,38 +151,76 @@ void cmSourceFileLocation::UpdateDirectory(const char* name)
     }
 }
 
+//----------------------------------------------------------------------------
+bool
+cmSourceFileLocation
+::MatchesAmbiguousExtension(cmSourceFileLocation const& loc) const
+{
+  // This location's extension is not ambiguous but loc's extension
+  // is.  See if the names match as-is.
+  if(this->Name == loc.Name)
+    {
+    return true;
+    }
+
+  // Check if loc's name could possibly be extended to our name by
+  // adding an extension.
+  if(!(this->Name.size() > loc.Name.size() &&
+       this->Name.substr(0, loc.Name.size()) == loc.Name &&
+       this->Name[loc.Name.size()] == '.'))
+    {
+    return false;
+    }
+
+  // Only a fixed set of extensions will be tried to match a file on
+  // disk.  One of these must match if loc refers to this source file.
+  std::string ext = this->Name.substr(loc.Name.size()+1);
+  cmMakefile* mf = this->Makefile;
+  const std::vector<std::string>& srcExts = mf->GetSourceExtensions();
+  if(std::find(srcExts.begin(), srcExts.end(), ext) != srcExts.end())
+    {
+    return true;
+    }
+  const std::vector<std::string>& hdrExts = mf->GetHeaderExtensions();
+  if(std::find(hdrExts.begin(), hdrExts.end(), ext) != hdrExts.end())
+    {
+    return true;
+    }
+  return false;
+}
+
 //----------------------------------------------------------------------------
 bool cmSourceFileLocation::Matches(cmSourceFileLocation const& loc)
 {
-  if(this->AmbiguousExtension || loc.AmbiguousExtension)
+  if(this->AmbiguousExtension && loc.AmbiguousExtension)
     {
-    // Need to compare without the file extension.
-    std::string thisName;
-    if(this->AmbiguousExtension)
+    // Both extensions are ambiguous.  Since only the old fixed set of
+    // extensions will be tried, the names must match at this point to
+    // be the same file.
+    if(this->Name != loc.Name)
       {
-      thisName = this->Name;
+      return false;
       }
-    else
-      {
-      thisName = cmSystemTools::GetFilenameWithoutLastExtension(this->Name);
     }
-    std::string locName;
-    if(loc.AmbiguousExtension)
+  else if(this->AmbiguousExtension)
     {
-      locName = loc.Name;
-      }
-    else
+    // Only "this" extension is ambiguous.
+    if(!loc.MatchesAmbiguousExtension(*this))
       {
-      locName = cmSystemTools::GetFilenameWithoutLastExtension(loc.Name);
+      return false;
       }
-    if(thisName != locName)
+    }
+  else if(loc.AmbiguousExtension)
+    {
+    // Only "loc" extension is ambiguous.
+    if(!this->MatchesAmbiguousExtension(loc))
       {
       return false;
       }
     }
   else
     {
-    // Compare with extension.
+    // Neither extension is ambiguous.
     if(this->Name != loc.Name)
       {
       return false;

Source/cmSourceFileLocation.h

@@ -94,6 +94,8 @@ private:
   std::string Directory;
   std::string Name;
 
+  bool MatchesAmbiguousExtension(cmSourceFileLocation const& loc) const;
+
   // Update the location with additional knowledge.
   void Update(cmSourceFileLocation const& loc);
   void Update(const char* name);