somebody is including this file inside an |extern "C"| declaration. That's bad. I can't find the culprit, but I can mark the important function |extern "C++"| to allow windows to compile.

xpcom/base/nsISupportsUtils.h

@@ -557,6 +557,8 @@ NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr)      \
 // A type-safe interface for calling |QueryInterface()|.  A similar implementation
 //	exists in "nsCOMPtr.h" for use with |nsCOMPtr|s.
 
+extern "C++" {
+
 class nsISupports;
 
 template <class T>
@@ -570,6 +572,8 @@ CallQueryInterface( nsISupports* aSource, T** aDestination )
 		return aSource->QueryInterface(T::GetIID(), aDestination);
 	}
 
+} // extern "C++"
+
 ////////////////////////////////////////////////////////////////////////////////
 
 #endif /* __nsISupportsUtils_h */

xpcom/glue/nsISupportsUtils.h

@@ -557,6 +557,8 @@ NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr)      \
 // A type-safe interface for calling |QueryInterface()|.  A similar implementation
 //	exists in "nsCOMPtr.h" for use with |nsCOMPtr|s.
 
+extern "C++" {
+
 class nsISupports;
 
 template <class T>
@@ -570,6 +572,8 @@ CallQueryInterface( nsISupports* aSource, T** aDestination )
 		return aSource->QueryInterface(T::GetIID(), aDestination);
 	}
 
+} // extern "C++"
+
 ////////////////////////////////////////////////////////////////////////////////
 
 #endif /* __nsISupportsUtils_h */

xpcom/public/nsISupportsUtils.h

@@ -557,6 +557,8 @@ NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr)      \
 // A type-safe interface for calling |QueryInterface()|.  A similar implementation
 //	exists in "nsCOMPtr.h" for use with |nsCOMPtr|s.
 
+extern "C++" {
+
 class nsISupports;
 
 template <class T>
@@ -570,6 +572,8 @@ CallQueryInterface( nsISupports* aSource, T** aDestination )
 		return aSource->QueryInterface(T::GetIID(), aDestination);
 	}
 
+} // extern "C++"
+
 ////////////////////////////////////////////////////////////////////////////////
 
 #endif /* __nsISupportsUtils_h */