[PATCH] D49653: [LLD] [COFF] Handle comdat sections without leader symbols

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo created this revision.
mstorsjo added reviewers: ruiu, rnk, pcc.

Discard them unless they have been associated by other means (yet unimplemented).

According to MS link.exe, such sections are illegal, but MinGW setups use them in their take on associative comdats.

This avoids leaving references to the bogus SectionChunk* PendingComdat, which cannot be dereferenced.

This fixes PR38183.


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D49653

Files:
  COFF/InputFiles.cpp
  test/COFF/pending-comdat.s


Index: test/COFF/pending-comdat.s
===================================================================
--- /dev/null
+++ test/COFF/pending-comdat.s
@@ -0,0 +1,21 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -triple=x86_64-windows-gnu %s -filetype=obj -o %t.obj
+
+# RUN: not lld-link -lldmingw -out:%t.exe -entry:main -subsystem:console %t.obj 2>&1 | FileCheck %s
+
+# CHECK: error: undefined symbol: other
+
+# Check that the comdat section without a symbol isn't left pending once we iterate symbols
+# to print source of the undefined symbol.
+
+	.text
+	.globl main
+main:
+	call other
+	ret
+
+	.section	.data$pending,"w"
+	.linkonce	discard
+.Llocal:
+	.byte	0
Index: COFF/InputFiles.cpp
===================================================================
--- COFF/InputFiles.cpp
+++ COFF/InputFiles.cpp
@@ -233,6 +233,12 @@
       return Symtab->addRegular(this, Name, Sym.getGeneric(), SC);
     return Symtab->addUndefined(Name, this, false);
   }
+  if (SC == PendingComdat) {
+    StringRef Name;
+    COFFObj->getSymbolName(Sym, Name);
+    log("comdat section " + Name + " without leader and unassociated, discarding");
+    return nullptr;
+  }
   if (SC)
     return make<DefinedRegular>(this, /*Name*/ "", false,
                                 /*IsExternal*/ false, Sym.getGeneric(), SC);


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