[PATCH] D108016: [lld-macho] Ignore LLVM segments to prevent duplicate syms

[Vincent Lee via Phabricator via llvm-commits]

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Cleanup wording


There was an instance of a third-party archive containing multiple _llvm symbols from 
different files that clashed with each other producing duplicate symbols. Symbols under 
the LLVM segment don't seem to be producing any meaningful value, so just ignore them.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108016

Files:
  lld/MachO/InputFiles.cpp
  lld/test/MachO/ignore-symbols.s


Index: lld/test/MachO/ignore-symbols.s
===================================================================
--- /dev/null
+++ lld/test/MachO/ignore-symbols.s
@@ -0,0 +1,20 @@
+# REQUIRES: x86
+# RUN: rm -rf %t; split-file %s %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo.s -o %t/foo.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/bar.s -o %t/bar.o
+
+## _llvm. symbols are not special. LLD would produce duplicate symbol errors
+## if they were not within the LLVM segment.
+# RUN: %lld -dylib %t/foo.o %t/bar.o -o %t/libDuplicate.dylib
+
+#--- foo.s
+.globl _llvm.foo
+.section __LLVM,__bitcode
+_llvm.foo:
+.asciz "test"
+
+#--- bar.s
+.globl _llvm.foo
+.section __LLVM,__bitcode
+_llvm.foo:
+.asciz "test"
Index: lld/MachO/InputFiles.cpp
===================================================================
--- lld/MachO/InputFiles.cpp
+++ lld/MachO/InputFiles.cpp
@@ -282,16 +282,20 @@
     } else {
       auto *isec =
           make<ConcatInputSection>(segname, name, this, data, align, flags);
-      if (!(isDebugSection(isec->getFlags()) &&
-            isec->getSegName() == segment_names::dwarf)) {
-        subsections.push_back({{0, isec}});
-      } else {
+      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. But we must still push an
         // empty map to ensure the indices line up for the remaining sections.
         subsections.push_back({});
         debugSections.push_back(isec);
+      } else if (isec->getSegName() == segment_names::llvm) {
+        // Sections within the llvm segment aren't known to induce symbols errors.
+        // Push an empty map to ensure indices line up for the remaining sections.
+        subsections.push_back({});
+      } else {
+        subsections.push_back({{0, isec}});
       }
     }
   }


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