1716549 - Improve MsaaAccessible::QueryInterface when the underlying Accessible is dead

Status: RESOLVED FIXED

(Core :: Disability Access APIs, defect, P1)

Description

[James Teh [:Jamie]]

I hit a debug assertion today and it made me realise that MsaaAccessible::QueryInterface could be a little more correct in its handling of interfaces when the underlying Accessible dies. Right now, even querying IUnknown returns E_NOINTERFACE in this case, which is probably bad COM etiquette at best, a violation of the rules at worst. For the core interfaces which don't involve checking the Accessible or creating a new object (IUnknown, IDispatch, IAccessible), we can return the interface even if the Accessible is dead.

Comment 1

[James Teh [:Jamie]]

Attachment: Bug 1716549: Make MsaaAccessible::QueryInterface return interfaces that are always available even if the underlying Accessible is dead.

Returning E_NOINTERFACE for IUnknown at least is probably bad form.
Also, mscom::Interceptor seems to expect IDispatch to always be available and asserts if it isn't.
We're seeing some weird COM crashes in the wild, and while I don't know if this will fix them, correctness seems like a good place to start.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1694865

Comment 3

[Marco Castelluccio [:marco]]

Morgan, can you land the patch yourself, since James is away?
James said it might help with bug 1713126.

Comment 4

[Morgan Reschenberg [:morgan]]

Yep, done :)

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f16d8d46efcb
Make MsaaAccessible::QueryInterface return interfaces that are always available even if the underlying Accessible is dead. r=morgan

Comment 6

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/f16d8d46efcb