1695275 - PLDHashTable destructor does not need to iterate through entries when entry is trivially destructible

Status: RESOLVED FIXED

(Core :: XPCOM, task)

Description

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

It seems unnecessary to zero the memory of removed entries such as is done by PLDHashTable::ClearEntryStub.
nsTHashtable::s_ClearEntry is already a no-op if EntryType is trivially destructible.

When we know that the clear operation is a no-op, we can skip iterating through all entries in PLDHashTable::~PLDHashTable entirely.

Comment 1

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

Attachment: Bug 1695275 - Simplify hashtable clearing when there is no Clear operation. r=#xpcom-reviewers

Depends on D106643

Comment 2

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

One thing I might have missed here is that when not clearing, but removing individual entries, it might be necessary to either zero them on removal or on initialization. This seems to be the case for XPCMaps, e.g.

Comment 3

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

Attachment: Bug 1695275 - Simplify hashtable clearing when EntryType is trivially destructible. r=#xpcom-reviewers

Depends on D106644

Comment 4

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

Attachment: Bug 1695275 - WIP: Disable clear operation in other cases. r=#xpcom-reviewers

Depends on D106647

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/affdc2d452ce
Simplify hashtable clearing when there is no Clear operation. r=xpcom-reviewers,nika
https://hg.mozilla.org/integration/autoland/rev/945a04ae3805
Simplify hashtable clearing when EntryType is trivially destructible. r=xpcom-reviewers,nika

Comment 6

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/affdc2d452ce
https://hg.mozilla.org/mozilla-central/rev/945a04ae3805