[lld] r338064 - [COFF] Handle comdat sections without leader symbols

[Martin Storsjo via llvm-commits]

Author: mstorsjo
Date: Thu Jul 26 13:14:50 2018
New Revision: 338064

URL: http://llvm.org/viewvc/llvm-project?rev=338064&view=rev
Log:
[COFF] Handle comdat sections without leader symbols

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

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.

Differential Revision: https://reviews.llvm.org/D49653

Added:
    lld/trunk/test/COFF/pending-comdat.s
Modified:
    lld/trunk/COFF/InputFiles.cpp

Modified: lld/trunk/COFF/InputFiles.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/InputFiles.cpp?rev=338064&r1=338063&r2=338064&view=diff
==============================================================================
--- lld/trunk/COFF/InputFiles.cpp (original)
+++ lld/trunk/COFF/InputFiles.cpp Thu Jul 26 13:14:50 2018
@@ -281,6 +281,13 @@ void ObjFile::initializeSymbols() {
     if (auto *Def = Sym.getSectionDefinition())
       if (Def->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
         readAssociativeDefinition(Sym, Def);
+    if (SparseChunks[Sym.getSectionNumber()] == PendingComdat) {
+      StringRef Name;
+      COFFObj->getSymbolName(Sym, Name);
+      log("comdat section " + Name +
+          " without leader and unassociated, discarding");
+      continue;
+    }
     Symbols[I] = createRegular(Sym);
   }
 

Added: lld/trunk/test/COFF/pending-comdat.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/pending-comdat.s?rev=338064&view=auto
==============================================================================
--- lld/trunk/test/COFF/pending-comdat.s (added)
+++ lld/trunk/test/COFF/pending-comdat.s Thu Jul 26 13:14:50 2018
@@ -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