coverage: Infer instances_used from pgo_func_name_var_map
#144530
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In obscure circumstances, we would sometimes emit a covfun record for a
function with no physical coverage counters, causing `llvm-cov` to fail with
the cryptic error message:
malformed instrumentation profile data: function name is empty
We can eliminate this mismatch by removing `instances_used` entirely, and
instead inferring its contents from the keys of `pgo_func_name_var_map`.
This makes it impossible for a "used" function to lack a PGO name entry.
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r? @SparrowLii rustbot has assigned @SparrowLii. Use |
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r? lqd This change looks good to me. It'd be better to have a test but we don't necessarily need it in this PR, as getting an MCVE from #141577 is not easy. Reducing the issue seems doable to me, but the current repro involving fuzzing is still quite involved, and it seems it'd be painful to produce a minimization in this current state. We should have such a test before relanding #144298 though, so the issue doesn't reappear a 3rd time. With that, @bors r+ |
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Rollup of 7 pull requests Successful merges: - #144072 (update `Atomic*::from_ptr` and `Atomic*::as_ptr` docs) - #144151 (`tests/ui/issues/`: The Issues Strike Back [1/N]) - #144300 (Clippy fixes for miropt-test-tools) - #144399 (Add a ratchet for moving all standard library tests to separate packages) - #144472 (str: Mark unstable `round_char_boundary` feature functions as const) - #144503 (Various refactors to the codegen coordinator code (part 3)) - #144530 (coverage: Infer `instances_used` from `pgo_func_name_var_map`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of #144530 - Zalathar:instances-used, r=lqd coverage: Infer `instances_used` from `pgo_func_name_var_map` In obscure circumstances involving macro-expanded spans, we would sometimes emit a covfun record for a function with no physical coverage counters, and therefore no corresponding entry in the “PGO names” section of the binary. The absence of that name entry causes `llvm-cov` to fail with the cryptic error message: ```text malformed instrumentation profile data: function name is empty ``` We can eliminate this mismatch by removing `instances_used` entirely, and instead inferring its contents from the keys of `pgo_func_name_var_map`. This makes it impossible for a "used" function to lack a PGO name entry. --- This is an attempt to eliminate the cause of #141577 when re-landing changes like #144298 in the future. I haven't been able to reproduce the underlying issue in an in-tree test, because the only known repro involves a non-trivial derive proc-macro that relies on `syn` and `proc-macro2`. But I have manually verified in a separate branch that this change would have prevented the reoccurrence of #141577 (comment).
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In obscure circumstances involving macro-expanded spans, we would sometimes emit a covfun record for a function with no physical coverage counters, and therefore no corresponding entry in the “PGO names” section of the binary. The absence of that name entry causes
llvm-covto fail with the cryptic error message:We can eliminate this mismatch by removing
instances_usedentirely, and instead inferring its contents from the keys ofpgo_func_name_var_map.This makes it impossible for a "used" function to lack a PGO name entry.
This is an attempt to eliminate the cause of #141577 when re-landing changes like #144298 in the future.
I haven't been able to reproduce the underlying issue in an in-tree test, because the only known repro involves a non-trivial derive proc-macro that relies on
synandproc-macro2. But I have manually verified in a separate branch that this change would have prevented the reoccurrence of #141577 (comment).