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_Unwind_FindEnclosingFunction fails on macOS #439

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Merged
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Oct 11, 2021
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_Unwind_FindEnclosingFunction fails on macOS #439

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15 changes: 9 additions & 6 deletions src/backtrace/libunwind.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,14 +55,17 @@ impl Frame {
return symbol_address;
}

// It seems that on OSX `_Unwind_FindEnclosingFunction` returns a
// pointer to... something that's unclear. It's definitely not always
// the enclosing function for whatever reason. It's not entirely clear
// to me what's going on here, so pessimize this for now and just always
// The macOS linker emits a "compact" unwind table that only includes an
// entry for a function if that function either has an LSDA or its
// encoding differs from that of the previous entry. Consequently, on
// macOS, `_Unwind_FindEnclosingFunction` is unreliable (it can return a
// pointer to some totally unrelated function). Instead, we just always
// return the ip.
//
// Note the `skip_inner_frames.rs` test is skipped on OSX due to this
// clause, and if this is fixed that test in theory can be run on OSX!
// https://github.com/rust-lang/rust/issues/74771#issuecomment-664056788
//
// Note the `skip_inner_frames.rs` test is skipped on macOS due to this
// clause, and if this is fixed that test in theory can be run on macOS!
if cfg!(target_os = "macos") || cfg!(target_os = "ios") {
self.ip()
} else {
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