66825 - nsConsoleService.h uses nsCOMPtr<nsSupportsArray>

Status: RESOLVED INVALID

(Core :: XPCOM, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

nsConsoleService.h has an nsCOMPtr<nsSupportsArray> member variable.  Shouldn't
this be an nsCOMPtr<ns*I*SupportsArray>?  I thought nsCOMPtr was supposed to be
used only for interface pointers.  (In fact, I thought things like this didn't
compile...)  This causes a build warning on mac (blamed to scc) because of the
operator= on nsDerivedSafe.

Comment 1

[Scott Collins]

See

  news://news.mozilla.org/[e-mail]

An |nsCOMPtr| over a concrete class is now sanctioned when the concrete class
satisfies certain properties.  The warning generated by |operator=| is sort of a
false-positive in this case.  Yes, interfaces should not define |operator=|,
because that's an invitation to slice.  It is valid and reasonable for a leaf
class to define |operator=|, and this is the rare case where someone wants both
at the same time, so my warning fires. ... oh well.

On the other hand, I don't see any reason why this code needs |mListeners| to be
a |nsCOMPtr<nsSupportsArray>|, so, although this is valid, it seems pointless. 
I'll attach a patch and test build this on a couple of platforms.

Comment 2

[Scott Collins]

Attachment: use the interface instead of the concrete type

Comment 3

[Scott Collins]

Here's why they do it: they want to call |RemoveElement| instead of first
finding the position, if any, of a matching element, and then calling
|RemoveElementAt|.  You can argue that this is right or wrong ... but probably
in a different bug.  I'm going to close this one out as INVALID.