Bug 84781 – objectProtoFuncToString creates new string every invocation

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Michael Saboff]

objectProtoFuncToString creates and returns a JSString with the contents of "[object <object_type]" (e.g. "[object Number]").  This creates a new string each time possibly increasing memory and using CPU.  This value should be created once and cached for each object.

[Michael Saboff]

Created attachment 138653 [details]
Patch

This fails the style checker due to using a PassRefPtr as a local, but reused pattern from JSStringBuilder.h.

[WebKit Review Bot]

Attachment 138653 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/JavaScriptCore/ChangeLog', u'Source..." exit_code: 1
Source/JavaScriptCore/runtime/ObjectPrototype.cpp:260:  Local variables should never be PassRefPtr (see http://webkit.org/coding/RefPtr.html).  [readability/pass_ptr] [5]
Total errors found: 1 in 4 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Geoffrey Garen]

Comment on attachment 138653 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=138653&action=review

Patch looks good, but some minor changes needed here before committing.

> Source/JavaScriptCore/runtime/ObjectPrototype.cpp:259
> +    if (!thisObject->structure()->hasObjectToStringValue()) {

Our typical style here is just to call objectToStringValue():
RefPtr<> toStringValue = thisObject->structure()->objectToStringValue();
if (!toStringValue) {
    ...
    toStringValue = ...
}
...

> Source/JavaScriptCore/runtime/ObjectPrototype.cpp:264
> +        thisObject->structure()->setObjectToStringValue(exec->globalData(), thisObject, jsNontrivialString(exec, result));

The appropriate pattern is to make the local a RefPtr, to avoid accidentally dereferencing NULL, and then use .release() when passing it to setObjectToStringValue here.

> Source/JavaScriptCore/runtime/Structure.cpp:797
> +#if 1

Please remove the #if.

[Michael Saboff]

Created attachment 138669 [details]
Updated Patch with Suggested Fixes

[Geoffrey Garen]

Comment on attachment 138669 [details]
Updated Patch with Suggested Fixes

r=me

[Early Warning System Bot]

Comment on attachment 138669 [details]
Updated Patch with Suggested Fixes

Attachment 138669 [details] did not pass qt-wk2-ews (qt):
Output: http://queues.webkit.org/results/12525366

[Michael Saboff]

Created attachment 138686 [details]
Updated patch with speculative Qt fix

[Michael Saboff]

Committed r115151: <http://trac.webkit.org/changeset/115151>