fix: detect DoubleCheckedLocking with !(x != null) outer guard - #6002
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arimu1 wants to merge 1 commit into
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fix: detect DoubleCheckedLocking with !(x != null) outer guard#6002arimu1 wants to merge 1 commit into
arimu1 wants to merge 1 commit into
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DoubleCheckedLocking matched outer null checks only as binary comparisons. The equivalent form !(x != null) was a false negative. Normalize LOGICAL_COMPLEMENT of NOT_EQUAL_TO against null the same as x == null. Fixes google#5963.
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Fixes #5963
Problem
DoubleCheckedLockingmatches the outer null guard by syntax. Thelogically equivalent form
!(x != null)(instead ofx == null) was afalse negative even though the double-checked locking pattern and unsafe
publication on a non-volatile field are unchanged.
Fix
In
getNullCheckedExpression, treat a logical complement of a!= nullcomparison the same as== null, after stripping parentheses.Test
positiveNegatedNotEqualsNullcovering the issue reproducer.mvn -pl core -am test -Dtest=DoubleCheckedLockingTest— 8/8 pass (JDK 21/25 toolchains).