1132655 - Don't allow conversions from DOMString to const string references

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Boris Zbarsky [:bzbarsky]]

DOMString is meant to be used as an outparam.  When converting it to a const string reference, what will happen is that its conversion operator to nsString& will get invoked and then the result will be treated as a const nsString&.

But the conversion operator to nsString& on DOMString is only supposed to be used if the DOMString doesn't contain any data, and asserts so.  Sadly, we have some codepaths that are clearly undertested...

In any case, the upshot is that you can only pass a DOMString to a const string ref without hitting asserts in the tree today if the DOMString is empty.  It's highly unlikely that anyone is currently doing that correctly.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Attachment: Don't allow conversions from DOMString to const XPCOM string references, since it's meant to be an outparam only

Comment 2

[Boris Zbarsky [:bzbarsky]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/ae4d683969e3

Comment 3

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/ae4d683969e3