From ed8298b825b8c2c5b57471cdd13dec9f94e26c03 Mon Sep 17 00:00:00 2001 From: Zalathar Date: Sun, 12 Nov 2023 18:07:28 +1100 Subject: [PATCH] coverage: Avoid creating malformed macro name spans This method is trying to detect macro invocations, so that it can split a span into two parts just after the `!` of the invocation. Under some circumstances (probably involving nested macros), it gets confused and produces a span that is larger than the original span, and possibly extends outside its enclosing function and even into an adjacent file. In extreme cases, that can result in malformed coverage mappings that cause `llvm-cov` to fail. For now, we at least want to detect these egregious cases and avoid them, so that coverage reports can still be produced. --- compiler/rustc_mir_transform/src/coverage/spans.rs | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/compiler/rustc_mir_transform/src/coverage/spans.rs b/compiler/rustc_mir_transform/src/coverage/spans.rs index 704eea413e1..b318134ae67 100644 --- a/compiler/rustc_mir_transform/src/coverage/spans.rs +++ b/compiler/rustc_mir_transform/src/coverage/spans.rs @@ -381,6 +381,12 @@ fn maybe_push_macro_name_span(&mut self) { let merged_prefix_len = self.curr_original_span.lo() - curr.span.lo(); let after_macro_bang = merged_prefix_len + BytePos(visible_macro.as_str().len() as u32 + 1); + if self.curr().span.lo() + after_macro_bang > self.curr().span.hi() { + // Something is wrong with the macro name span; + // return now to avoid emitting malformed mappings. + // FIXME(#117788): Track down why this happens. + return; + } let mut macro_name_cov = curr.clone(); self.curr_mut().span = curr.span.with_lo(curr.span.lo() + after_macro_bang); macro_name_cov.span =