1096095 - nsTArray should support in-place construction

Status: RESOLVED DUPLICATE of bug 1571759

(Core :: XPCOM, defect)

Description

[Xidorn Quan [:xidorn] UTC+10]

Some classes do not have reliable copy or move ctors (e.g. nsLineLayout), which makes it hard to store them in nsTArray. I suggest that nsTArray should have methods for in-place construction for those types to avoid using copy ctors.

The current workaround could be wraping a Maybe, which supports in-place construction, inside the nsTArray. But I don't think it's an optimal way.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Doesn't AppendElement() with no argument do in-place construction?

Comment 2

[Xidorn Quan [:xidorn] UTC+10]

(In reply to Please do not ask for reviews for a bit [:bz] from comment #1)
> Doesn't AppendElement() with no argument do in-place construction?

Yes, but I meant in-place construction with parameter, like Maybe::emplace.

Well, I no longer think it is useful now, since classes which cannot be copied or moved should never be directly stored in a nsTArray.

Comment 3

[Simon Giesecke [:sg] [he/him]]

In the meantime, nsTArray_Impl::EmplaceBack was added.