<div dir="ltr">I encountered a segfault when using lld to cross-compile for Windows (+MinGW) from Linux.  The problem happens with objects built by gcc.  The problem is that ObjFile::CreateRegular considers a PendingComdat to be valid (and later causes an illegal pointer dereference).  The following patch fixes the crash:<div><br></div><div><div>diff --git a/COFF/InputFiles.cpp b/COFF/InputFiles.cpp</div><div>index 9e2345b0a..f47d612df 100644</div><div>--- a/COFF/InputFiles.cpp</div><div>+++ b/COFF/InputFiles.cpp</div><div>@@ -229,11 +229,11 @@ Symbol *ObjFile::createRegular(COFFSymbolRef Sym) {</div><div>   if (Sym.isExternal()) {</div><div>     StringRef Name;</div><div>     COFFObj->getSymbolName(Sym, Name);</div><div>-    if (SC)</div><div>+    if (SC && SC != PendingComdat)</div><div>       return Symtab->addRegular(this, Name, Sym.getGeneric(), SC);</div><div>     return Symtab->addUndefined(Name, this, false);</div><div>   }</div><div>-  if (SC)</div><div>+  if (SC && SC != PendingComdat)</div><div>     return make<DefinedRegular>(this, /*Name*/ "", false,</div><div>                                 /*IsExternal*/ false, Sym.getGeneric(), SC);</div><div>   return nullptr;</div></div><div><br></div><div>I can upload this to Phabricator in case this is the right fix.  If not, I'll upload a reproducer for further investigation.  (I omitted it to avoid manually packaging a whole set of object files - I think --reproduce=<repro> doesn't work on Windows yet).</div><div><br></div><div>For reference, here's the segfault:</div><div><div>#0 0x0000000000500999 llvm::sys::PrintStackTrace(llvm::raw_ostream&) /ssd2/pirama/ll$</div><div>m-upstream/llvm/lib/Support/Unix/Signals.inc:488:11                         </div><div>#1 0x0000000000500b49 PrintStackTraceSignalHandler(void*) /ssd2/pirama/llvm-upstream$</div><div>llvm/lib/Support/Unix/Signals.inc:552:1          </div><div>#2 0x00000000004ff1d6 llvm::sys::RunSignalHandlers() /ssd2/pirama/llvm-upstream/llvm$</div><div>lib/Support/Signals.cpp:66:5                                 </div><div>#3 0x0000000000500eb7 SignalHandler(int) /ssd2/pirama/llvm-upstream/llvm/lib/Support$</div><div>Unix/Signals.inc:351:1        </div><div>#4 0x00007fc7bfaff0c0 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x110c0)</div><div>#5 0x00000000005fe370 lld::coff::DefinedRegular::getChunk() const /ssd2/pirama/llvm-$</div><div>pstream/llvm/tools/lld/COFF/Symbols.h:169:43                                         </div><div>#6 0x00000000005fe082 lld::coff::Defined::getChunk() /ssd2/pirama/llvm-upstream/llvm$</div><div>tools/lld/COFF/Symbols.h:381:5                                                       </div><div>#7 0x0000000000656114 (anonymous namespace)::Writer::createSymbol(lld::coff::Defined$</div><div>) /ssd2/pirama/llvm-upstream/llvm/tools/lld/COFF/Writer.cpp:617:42                   </div><div>#8 0x000000000064c7df (anonymous namespace)::Writer::createSymbolAndStringTable() /s$</div><div>d2/pirama/llvm-upstream/llvm/tools/lld/COFF/Writer.cpp:0:43                          </div><div>#9 0x00000000006499f9 (anonymous namespace)::Writer::run() /ssd2/pirama/llvm-upstrea$</div><div>/llvm/tools/lld/COFF/Writer.cpp:342:3                                                </div><div>#10 0x0000000000649843 lld::coff::writeResult() /ssd2/pirama/llvm-upstream/llvm/tool$</div><div>/lld/COFF/Writer.cpp:232:31                                                          </div><div>#11 0x00000000005d1268 lld::coff::LinkerDriver::link(llvm::ArrayRef<char const*>) /s$</div><div>d2/pirama/llvm-upstream/llvm/tools/lld/COFF/Driver.cpp:1536:3</div><div>#12 0x00000000005c8687 lld::coff::link(llvm::ArrayRef<char const*>, bool, llvm::raw_$</div><div>stream&) /ssd2/pirama/llvm-upstream/llvm/tools/lld/COFF/Driver.cpp:75:7</div><div>#13 0x0000000000946db0 lld::mingw::link(llvm::ArrayRef<char const*>, llvm::raw_ostrea</div><div>m&) /ssd2/pirama/llvm-upstream/llvm/tools/lld/MinGW/Driver.cpp:255:10</div><div>#14 0x00000000004d02a8 main /ssd2/pirama/llvm-upstream/llvm/tools/lld/tools/lld/lld.c</div><div>pp:121:14</div></div></div>