Fix to 49416.

Emit NS_NO_VTABLE in xpidl-generated interface files.  NS_NO_VTABLE is defined in nsISupportsUtils.h, and on windows generates __declspec(novtable).

This saves us some code space, and may also be a runtime win.

Initial version of this fix courtesy Adam Lock <adamlock@netscape.com>.

r=jband
a=beard


NOTE this change will cause the world to recompile.

xpcom/base/nsISupportsUtils.h

@@ -70,6 +70,17 @@ typedef unsigned long nsrefcnt;
 typedef PRUint32 nsrefcnt;
 #endif
 
+/**
+ * NS_NO_VTABLE is emitted by xpidl in interface declarations whenever xpidl
+ * can determine that the interface can't contain a constructor.  This results
+ * in some space savings and possible runtime savings - see bug 49416.
+ */
+#if defined(_MSC_VER) && _MSC_VER >= 1100
+#define NS_NO_VTABLE __declspec(novtable)
+#else
+#define NS_NO_VTABLE
+#endif
+
 #include "nsTraceRefcnt.h"
 
 /**
@@ -78,7 +89,7 @@ typedef PRUint32 nsrefcnt;
  * and a reference counted memory model (AddRef/Release). This is
  * modelled after the win32 IUnknown API.
  */
-class nsISupports {
+class NS_NO_VTABLE nsISupports {
 public:
 
   /**

xpcom/glue/nsISupportsUtils.h

@@ -70,6 +70,17 @@ typedef unsigned long nsrefcnt;
 typedef PRUint32 nsrefcnt;
 #endif
 
+/**
+ * NS_NO_VTABLE is emitted by xpidl in interface declarations whenever xpidl
+ * can determine that the interface can't contain a constructor.  This results
+ * in some space savings and possible runtime savings - see bug 49416.
+ */
+#if defined(_MSC_VER) && _MSC_VER >= 1100
+#define NS_NO_VTABLE __declspec(novtable)
+#else
+#define NS_NO_VTABLE
+#endif
+
 #include "nsTraceRefcnt.h"
 
 /**
@@ -78,7 +89,7 @@ typedef PRUint32 nsrefcnt;
  * and a reference counted memory model (AddRef/Release). This is
  * modelled after the win32 IUnknown API.
  */
-class nsISupports {
+class NS_NO_VTABLE nsISupports {
 public:
 
   /**

xpcom/typelib/xpidl/xpidl_header.c

@@ -113,6 +113,7 @@ interface(TreeState *state)
     char *classNameImpl = NULL;
     char *cp;
     gboolean ok = TRUE;
+    gboolean keepvtable;
     const char *iid;
     const char *name_space;
     struct nsID id;
@@ -175,8 +176,29 @@ interface(TreeState *state)
     if (doc_comments != NULL)
         printlist(state->file, doc_comments);
 
+    /*
+     * NS_NO_VTABLE is defined in nsISupportsUtils.h, and defined on windows
+     * to __declspec(novtable) on windows.  This optimization is safe
+     * whenever the constructor calls no virtual methods.  Writing in IDL
+     * almost guarantees this, except for the case when a %{C++ block occurs in
+     * the interface.  We detect that case, and emit a macro call that disables
+     * the optimization.
+     */
+    keepvtable = FALSE;
+    for (iter = IDL_INTERFACE(state->tree).body;
+         iter != NULL;
+         iter = IDL_LIST(iter).next)
+    {
+        IDL_tree data = IDL_LIST(iter).data;
+        if (IDL_NODE_TYPE(data) == IDLN_CODEFRAG)
+            keepvtable = TRUE;
+    }
+    
     /* The interface declaration itself. */
-    fprintf(state->file, "class %s", className);
+    fprintf(state->file,
+            "class %s%s",
+            (keepvtable ? "" : "NS_NO_VTABLE "), className);
+    
     if ((iter = IDL_INTERFACE(iface).inheritance_spec)) {
         fputs(" : ", state->file);
         if (IDL_LIST(iter).next != NULL) {