[lld] [lld-macho] Fix crash with DWARF section-relative relocations (PR #168075)

[Jez Ng via llvm-commits]

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@@ -411,10 +411,14 @@ void ObjFile::parseSections(ArrayRef<SectionHeader> sectionHeaders) {
       auto *isec = make<ConcatInputSection>(section, data, align);
       if (isDebugSection(isec->getFlags()) &&
           isec->getSegName() == segment_names::dwarf) {
-        // Instead of emitting DWARF sections, we emit STABS symbols to the
-        // object files that contain them. We filter them out early to avoid
-        // parsing their relocations unnecessarily.
+        // Keep debug sections in debugSections for diagnostic purposes
         debugSections.push_back(isec);
+        // Add DWARF sections to subsections so their relocations are processed,
+        // but mark them dead so they aren't emitted (MachO uses STABS, not DWARF).
+        // This fixes crashes with section-relative relocations (e.g., DW_FORM_strp)
+        // while maintaining MachO's traditional STABS-only debug output.
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int3 wrote:

"fixes crashes" here will not make sense to future readers who did not know how the code looked like before. let's explain it directly here; my understanding is that we cannot simply drop the sections here because it would result in a "dangling reference" issue if other sections contain relocations that point to this one

https://github.com/llvm/llvm-project/pull/168075