345123 - Why does class nsGetterAddRefs<T> have an nsISupports**() operator anyway?

Status: RESOLVED FIXED

(Core :: XPCOM, defect, P5)

Description

[[e-mail]]

Spun off from bug 344949 comment 7.

Bug 344949 was caused by the following code snippet:
  nsCOMPtr<nsIXULTemplateResult> nextresult;
  rv = results->GetNext(getter_AddRefs(nextresult));
GetNext takes an nsISupports** so this construct reinterpreted the return value as an nsIXULTemplateResult. This was not noticed at the time because a) the code compiles (which is this bug) and b) it was only tested using an enumerator that enumerated objects whose nsISupports pointer was statically cast from their nsIXULTemplateResult pointer.

Comment 1

[:Gavin Sharp [email: [e-mail]]]

(In reply to comment #0)
> Spun off from bug 344949 comment 7.

I think you mean bug 344939 comment 7 :)

Comment 2

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Attachment: Patch

Yeah, this operator nsISupports** is crazy.

Comment 3

[[e-mail]]

Comment on attachment 820770 [details] [diff] [review]
Patch

There are a lot of calls to ReadObject there. Maybe we should change the signature to void readObject(in boolean aIsStrongRef, in nsIIDRef uuid, [retval, iid_is(uuid)] out nsQIResult object);

Comment 4

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Perhaps.  I'd prefer to do that elsewhere though.

Comment 5

[(no longer active)]

This looks great, but I don't understand why you're commenting the method out instead of removing it.

Comment 6

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Oh, yeah, that's silly.  I'll actually remove it when I land.

Comment 7

[(no longer active)]

(In reply to comment #6)
> Oh, yeah, that's silly.  I'll actually remove it when I land.

You rock!

Comment 8

[Masatoshi Kimura [:emk]]

Why is this not landed yet?

Comment 9

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Because I forgot about it.  I'll land it next time I push.

Comment 10

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Needed some rebasing.

https://hg.mozilla.org/integration/mozilla-inbound/rev/1123c64bca9e

Comment 11

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

https://hg.mozilla.org/mozilla-central/rev/1123c64bca9e

Comment 12

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

And an attempt to make comm-central build: https://hg.mozilla.org/comm-central/rev/e67da9f094ff