1689140 - SliceBudget::counter has smaller range than WorkBudget::budget on 32-bit platforms

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect)

Description

[Jon Coppeard (:jonco) (PTO until Tuesday 29th)]

When we create a SliceBudget based on a WorkBudget, we assign counter from the budget:

https://searchfox.org/mozilla-central/source/js/src/gc/GC.cpp#3004

Unfortunately, counter is a intptr_t and budget is int64_t, so there is the potential for this to go wrong.

Work budgets are mainly used for testing (e.g. in zeal modes) and any sensible budget will fit in 32 bits so it's unlikely this is causing a problem.

Comment 1

[Jon Coppeard (:jonco) (PTO until Tuesday 29th)]

Attachment: Bug 1689140 - Refactor SliceBudget API r?sfink

This patch does several things:

• make the counter type int64_t like the work budget parameter (the original purpose of this bug)
• simplify implementation by using a Variant to discriminate between different kinds of budget
• remove the global initialization
• remove makeUnlimited() (and replace uses with assignment from SliceBudget::unlimited())
• add convenience methods to get the original budget parameters
• add basic API tests

The use of Variant had the consequence that we now have to pass SliceBudget by reference now to make the linter happy.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/57cfe8a49a44
Refactor SliceBudget API r=sfink

Comment 3

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/57cfe8a49a44