1463287 - Add QueryInterface helper macro for concrete class types

Status: RESOLVED FIXED

(Core :: XPCOM, enhancement)

Description

[Kris Maglione [:kmag]]

We have a log of QueryInterface methods which implement querying to concrete class types which can't be unambiguously cast to nsISupports, and need to be used with RefPtr/do_QueryObject. Those can't be implemented with existing helper macros, and as a result have several ad-hoc (sometimes slightly dodgy) implementations across the tree.

We should have a helper macro for this, and make sure that the logic that it implements is sane.

Comment 1

[Kris Maglione [:kmag]]

Attachment: Bug 1463287: Add QueryInterface helper macro for concrete class types.

Using concrete class types with static IIDs in QueryInterface methods is a
pretty common pattern which isn't supported by any existing helper macros.
That's lead to separate ad-hoc implementations, with varying degrees of
dodginess, being scattered around the tree.

This patch adds a helper macro with a canonical (and safe) implementation, and
updates existing ad-hoc users to use it.

Review commit: https://reviewboard.mozilla.org/r/245568/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/245568/

Comment 2

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8979403 [details]
Bug 1463287: Add QueryInterface helper macro for concrete class types.

https://reviewboard.mozilla.org/r/245568/#review251656

r=me

I guess the various URI classes use hardcoded CID values which are not NS_GET_IID on the relevant class, which is why we can't use the macro for those?

I do think we can use it for nsDocLoader, though.

Comment 3

[Kris Maglione [:kmag]]

(In reply to Boris Zbarsky [:bz] (no decent commit message means r-) from comment #2)
> I guess the various URI classes use hardcoded CID values which are not
> NS_GET_IID on the relevant class, which is why we can't use the macro for
> those?

Right. Although we should probably fix that.

> I do think we can use it for nsDocLoader, though.

Yeah, that one didn't show up in my greps.

Comment 4

[Kris Maglione [:kmag]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/a1bf5dfd3c00c5e59a59272fb03d0d6684539b82
Bug 1463287: Add QueryInterface helper macro for concrete class types. r=bz

Comment 5

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/a1bf5dfd3c00