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rustc_codegen_llvm: Give each codegen unit a unique DWARF name on all platforms, not just Apple ones. #92024

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Dec 18, 2021
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rustc_codegen_llvm: Give each codegen unit a unique DWARF name on all platforms, not just Apple ones. #92024

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27 changes: 19 additions & 8 deletions compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1036,14 +1036,25 @@ pub fn compile_unit_metadata(
None => PathBuf::from(&*tcx.crate_name(LOCAL_CRATE).as_str()),
};

// The OSX linker has an idiosyncrasy where it will ignore some debuginfo
// if multiple object files with the same `DW_AT_name` are linked together.
// As a workaround we generate unique names for each object file. Those do
// not correspond to an actual source file but that is harmless.
if tcx.sess.target.is_like_osx {
name_in_debuginfo.push("@");
name_in_debuginfo.push(codegen_unit_name);
}
// To avoid breaking split DWARF, we need to ensure that each codegen unit
// has a unique `DW_AT_name`. This is because there's a remote chance that
// different codegen units for the same module will have entirely
// identical DWARF entries for the purpose of the DWO ID, which would
// violate Appendix F ("Split Dwarf Object Files") of the DWARF 5
// specification. LLVM uses the algorithm specified in section 7.32 "Type
// Signature Computation" to compute the DWO ID, which does not include
// any fields that would distinguish compilation units. So we must embed
// the codegen unit name into the `DW_AT_name`. (Issue #88521.)
//
// Additionally, the OSX linker has an idiosyncrasy where it will ignore
// some debuginfo if multiple object files with the same `DW_AT_name` are
// linked together.
//
// As a workaround for these two issues, we generate unique names for each
// object file. Those do not correspond to an actual source file but that
// is harmless.
name_in_debuginfo.push("@");
name_in_debuginfo.push(codegen_unit_name);

debug!("compile_unit_metadata: {:?}", name_in_debuginfo);
let rustc_producer =
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