2060852 - Crash in [@ mozilla::StyleHeaderSlice<T>::operator==]

Status: NEW

(Core :: CSS Parsing and Computation, defect)

Description

[BugBot [:suhaib / :marco]]

Crash report: https://crash-stats.mozilla.org/report/index/ac2ebaca-8176-4b2e-aec3-3f05d0260805

Reason: EXCEPTION_ACCESS_VIOLATION_READ

Top 10 frames of crashing thread:

0  xul.dll  mozilla::StyleHeaderSlice<unsigned long long, mozilla::StyleCustomIdent>::operator== const  layout/style/ServoStyleConstsInlines.h:230
0  xul.dll  mozilla::StyleArc<mozilla::StyleHeaderSlice<unsigned long long, mozilla::StyleCustomIdent> >::operator== const  layout/style/ServoStyleConsts.h:7448
0  xul.dll  mozilla::StyleArc<mozilla::StyleHeaderSlice<unsigned long long, mozilla::StyleCustomIdent> >::operator!= const  layout/style/ServoStyleConsts.h:7451
0  xul.dll  mozilla::StyleArcSlice<mozilla::StyleCustomIdent>::operator!= const  layout/style/ServoStyleConsts.h:7474
0  xul.dll  mozilla::StyleViewTransitionClassList::operator!= const  layout/style/ServoStyleConsts.h:29731
0  xul.dll  nsStyleUIReset::CalcDifference const  layout/style/nsStyleStruct.cpp:3496
0  xul.dll  mozilla::ComputedStyle::CalcStyleDifference const  layout/style/ComputedStyle.cpp:153
1  xul.dll  Gecko_CalcStyleDifference  layout/style/GeckoBindings.cpp:323
2  xul.dll  style::gecko::restyle_damage::GeckoRestyleDamage::compute_style_difference  servo/components/style/gecko/restyle_damage.rs:53
2  xul.dll  style::matching::MatchMethods::compute_style_difference  servo/components/style/matching.rs:1210

By querying Nightly crashes reported within the last 2 months, here are some insights about the signature:

• First crash report: 2026-06-25
• Process type: Multiple distinct types
• Is startup crash: No
• Has user comments: No
• Is null crash: Yes - 1 out of 4 crashes happened on null or near null memory address

Comment 1

[BugBot [:suhaib / :marco]]

The Bugbug bot thinks this bug should belong to the 'Core::CSS Parsing and Computation' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Jonathan Kew [:jfkthame]]

Looks like a longstanding issue, but not excessively high-frequency.