Ignore unwinding edges when checking for unconditional recursion #92889
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tmiasko force-pushed the unbounded-recursion branch from 67a3bdd to 016bda4 Compare The unconditional recursion lint determines if all execution paths eventually lead to a self-recursive call. The implementation always follows unwinding edges which limits its practical utility. For example, it would not lint function `f` because a call to `g` might unwind. It also wouldn't lint function `h` because an overflow check preceding the self-recursive call might unwind: ```rust pub fn f() { g(); f(); } pub fn g() { /* ... */ } pub fn h(a: usize) { h(a + 1); } ``` To avoid the issue, assume that terminators that might continue execution along non-unwinding edges do so. tmiasko force-pushed the unbounded-recursion branch from 016bda4 to 10b722c Compare 
| This seems strictly better while preserving existing behavior for the cases in #54444. There might be an interpretation of "lints have zero false positives" and "unconditional recursion" that would cause people to disagree with this change, but I think that interpretation is too narrow. Thanks tmiasko! @bors r+ rollup |
| 📌 Commit 10b722c has been approved by |
bors added S-waiting-on-bors | ☀️ Test successful - checks-actions |
| Finished benchmarking commit (21b4a9c): comparison url. Summary: This benchmark run shows 36 relevant regressions 😿 to instruction counts.
If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf. Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression |
| The performance regression will be addressed by changes from #93381. @rustbot label: +perf-regression-triaged |
rustbot added the perf-regression-triaged 7 participants
The unconditional recursion lint determines if all execution paths
eventually lead to a self-recursive call.
The implementation always follows unwinding edges which limits its
practical utility. For example, it would not lint function
fbecause acall to
gmight unwind. It also wouldn't lint functionhbecause anoverflow check preceding the self-recursive call might unwind:
To avoid the issue, assume that terminators that might continue
execution along non-unwinding edges do so.
Fixes #78474.