Move privateTemplateUniqueKey / sharedTemplateUniqueKey to .bss section

Source/bindings/scripts/code_generator_v8.pm

Index: Source/bindings/scripts/code_generator_v8.pm
diff --git a/Source/bindings/scripts/code_generator_v8.pm b/Source/bindings/scripts/code_generator_v8.pm
index 8d63d0b946603ac7004090d8a26b81b0805ffd17..8bb05dbaa25f8ee9f298de04e17259577bf2d483 100644
--- a/Source/bindings/scripts/code_generator_v8.pm
+++ b/Source/bindings/scripts/code_generator_v8.pm
@@ -1186,7 +1186,7 @@ sub GenerateDomainSafeFunctionGetter
 static void ${funcName}AttributeGetter(v8::Local<v8::String> name, const v8::PropertyCallbackInfo<v8::Value>& info)
 {
     // This is only for getting a unique pointer which we can pass to privateTemplate.
-    static const char* privateTemplateUniqueKey = "${funcName}PrivateTemplate";
+    static const int privateTemplateUniqueKey = 0;

[digit1, 2013/10/19 08:04:17]

This looks really good.

For the record, you can also avoid allocating a new global constant variable
entirely if you use the current function's address as the unique key (instead of
the address of an unused constant variable). This also makes the code slightly
smaller because compute the function address is easy in a PIC shared library,
while accessing the variable's address typically requires a GOT indirection and
one more memory load.

There are apparently only six variables affected by this patch, so that might
not be high priority, but consider this for future generator changes :) 

[Inactive, 2013/10/22 14:25:42]

So it looks like msvc optimizes out the static variable if I mark it as const.
Thus the failures. One solution would be to not mark it as const. This would
still get rid of the relocations but it would not move them to .rodata sections
:/

Taking the address of the current static function sounds interesting. One issue
is that we sometimes need 2 identifiers in the same function:
privateTemplateUniqueKey and sharedTemplateUniqueKey (see below). Those need to
be different.

     WrapperWorldType currentWorldType = worldType(info.GetIsolate());
     V8PerIsolateData* data = V8PerIsolateData::from(info.GetIsolate());
     v8::Handle<v8::FunctionTemplate> privateTemplate = data->privateTemplate(currentWorldType, &privateTemplateUniqueKey, $newTemplateParams, $functionLength);
@@ -1200,7 +1200,7 @@ static void ${funcName}AttributeGetter(v8::Local<v8::String> name, const v8::Pro
     }
     ${implClassName}* imp = ${v8ClassName}::toNative(holder);
     if (!BindingSecurity::shouldAllowAccessToFrame(imp->frame(), DoNotReportSecurityError)) {
-        static const char* sharedTemplateUniqueKey = "${funcName}SharedTemplate";
+        static const int sharedTemplateUniqueKey = 0;
         v8::Handle<v8::FunctionTemplate> sharedTemplate = data->privateTemplate(currentWorldType, &sharedTemplateUniqueKey, $newTemplateParams, $functionLength);
         v8SetReturnValue(info, sharedTemplate->GetFunction());
         return;
@@ -2994,7 +2994,7 @@ END
 v8::Handle<v8::FunctionTemplate> ${v8ClassName}Constructor::GetTemplate(v8::Isolate* isolate, WrapperWorldType currentWorldType)
 {
     // This is only for getting a unique pointer which we can pass to privateTemplate.
-    static const char* privateTemplateUniqueKey = "${v8ClassName}Constructor::GetTemplatePrivateTemplate";
+    static const int privateTemplateUniqueKey = 0;
     V8PerIsolateData* data = V8PerIsolateData::from(isolate);
     v8::Handle<v8::FunctionTemplate> result = data->privateTemplateIfExists(currentWorldType, &privateTemplateUniqueKey);
     if (!result.IsEmpty())