1998636 - Evaluate using std::unique_ptr instead of mozilla::StaticAutoPtr

Status: RESOLVED FIXED

(Core :: XPCOM, task)

Description

[[:sergesanspaille]]

StaticAutoPtr is equivalent to std::unique_ptr as the latter has a constexpr default constructor

Comment 1

[Andrew McCreight [:mccr8]]

StaticAutoPtr is XPCOM, not MFBT.

Comment 2

[Nika Layzell [:nika] (ni? for response)]

(In reply to [:sergesanspaille] from comment #0)

StaticAutoPtr is equivalent to std::unique_ptr as the latter has a constexpr default constructor

This is not true, as std::unique_ptr has a destructor, which StaticAutoPtr does not. If you are converting to std::unique_ptr, you need to make a NeverDestroyed<std::unique_ptr> to disable the static destructor so we don't introduce new static destructors.

Static destructors like this waste memory by adding new entries, and can cause weird bugs in code which doesn't fast-exit, as they'll run as the process exits.

I do not think that a straight replacement of StaticAutoPtr with std::unique_ptr is a good idea, in fact I would prefer to do the opposite, and convert more static std::unique_ptr instances to remove the static destructors.

Comment 3

[[:sergesanspaille]]

Attachment: Bug 1998636 - Improve documentation of StaticAutoPtr r=nika

In particular make it clear that it behaves differently from
std::unique_ptr in termes of destructor.

Comment 4

[[:sergesanspaille]]

Indeed! I updated the internal documentation and cancelled the associated child bugs.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/23e14949c918
https://hg.mozilla.org/integration/autoland/rev/056daff7a912
Improve documentation of StaticAutoPtr r=nika

Comment 6

[Iulian Moraru]

https://hg.mozilla.org/mozilla-central/rev/056daff7a912