403290 - "WARNING: nsDOMClassInfo::GetProperty Don't call me!" with __proto__

Status: RESOLVED WORKSFORME

Description

[Jesse Ruderman]

Created attachment 288101 [details]
testcase

WARNING: nsDOMClassInfo::GetProperty Don't call me!: file /Users/jruderman/trunk/mozilla/dom/src/base/nsDOMClassInfo.cpp, line 3701

This was turned from an assertion to a warning in bug 327571, but I can't trigger the warning with the testcase from that bug any more.

Comment 1

[Boris Zbarsky [:bzbarsky, bz on IRC]]

This is kinda fun.  The proto chain here looks something like this:

  A.__proto__ == B

B's class has a getProperty hook.

We do a property get on A, end up resolving the property on B, and call the getProperty hook for B's class, passing it A as the JSObject*.

This getProperty hook is XPC_WN_Helper_GetProperty.  It assumes that since it got called the passed-in object had WantGetProperty() set, so it calls the scriptable helper GetProperty.

The problem is that WantGetProperty() was on B, but since A was passed to the hook we call A's scriptable helper, which doesn't expect to ever be called.  Hence the warning.

This seems pretty bad to me; I think the scriptable helpers really do tend to assume that they get the JSObject for the right class, no?

Comment 2

[Serge Gautherie (:sgautherie)]

Would this and bug 311229 be duplicates ?

Comment 3

[Jesse Ruderman]

WFM

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.3a5pre) Gecko/20100602 Minefield/3.7a5pre