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ExprAttrs::eval: Don't write to the shared empty Bindings #537

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Merged
edolstra merged 1 commit into from
Jul 6, 2026
+6 −1
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ExprAttrs::eval: Don't write to the shared empty Bindings #537

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7 changes: 6 additions & 1 deletion src/libexpr/eval.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1366,7 +1366,12 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
sort = true;
}

bindings.bindings->pos = pos;
/* Empty attrsets share the static Bindings::emptyBindings, which we
must not write to: apart from being a data race, it causes false
sharing on emptyBindings' cache line (which may also hold other hot
globals such as Counter::enabled) between all evaluator threads. */
if (bindings.bindings != &Bindings::emptyBindings)
bindings.bindings->pos = pos;

v.mkAttrs(sort ? bindings.finish() : bindings.alreadySorted());
}
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