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Fix atomicity violations in concurrent cache operations #1559

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Merged
merged 1 commit into from
Sep 19, 2025
Merged

Fix atomicity violations in concurrent cache operations #1559

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8 changes: 6 additions & 2 deletions src/command_helpers.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,12 @@ impl CargoOutput {
}

pub(crate) fn print_debug(&self, arg: &dyn Display) {
if self.metadata && !self.checked_dbg_var.load(Ordering::Relaxed) {
self.checked_dbg_var.store(true, Ordering::Relaxed);
if self.metadata
&& self
.checked_dbg_var
.compare_exchange(false, true, Ordering::Relaxed, Ordering::Relaxed)
.is_ok()
{
println!("cargo:rerun-if-env-changed=CC_ENABLE_DEBUG_OUTPUT");
}
if self.debug {
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5 changes: 2 additions & 3 deletions src/lib.rs
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Expand Up @@ -4326,9 +4326,8 @@ fn is_disabled() -> bool {
0 => {
let truth = compute_is_disabled();
let encoded_truth = if truth { 2u8 } else { 1 };
// Might race against another thread, but we'd both be setting the
// same value so it should be fine.
CACHE.store(encoded_truth, Relaxed);
// Use compare_exchange to avoid race condition
let _ = CACHE.compare_exchange(0, encoded_truth, Relaxed, Relaxed);
truth
}
_ => unreachable!(),
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