Don't crash on broken debug info.

llvm-svn: 319367

lld/ELF/GdbIndex.cpp

@@ -68,14 +68,17 @@ LLDDwarfObj<ELFT>::findAux(const InputSectionBase &Sec, uint64_t Pos,
   uint32_t SymIndex = Rel.getSymbol(Config->IsMips64EL);
   const typename ELFT::Sym &Sym = File->getELFSyms()[SymIndex];
   uint32_t SecIndex = File->getSectionIndex(Sym);
-  Symbol &B = File->getRelocTargetSym(Rel);
-  auto &DR = cast<Defined>(B);
-  uint64_t Val = DR.Value + getAddend<ELFT>(Rel);
+
+  // Broken debug info can point to a non-Defined symbol, just ignore it.
+  auto *DR = dyn_cast<Defined>(&File->getRelocTargetSym(Rel));
+  if (!DR)
+    return None;
+  uint64_t Val = DR->Value + getAddend<ELFT>(Rel);
 
   // FIXME: We should be consistent about always adding the file
   // offset or not.
-  if (DR.Section->Flags & ELF::SHF_ALLOC)
-    Val += cast<InputSection>(DR.Section)->getOffsetInFile();
+  if (DR->Section->Flags & ELF::SHF_ALLOC)
+    Val += cast<InputSection>(DR->Section)->getOffsetInFile();
 
   return RelocAddrEntry{SecIndex, Val};
 }

lld/test/ELF/undef-broken-debug.test

@@ -0,0 +1,44 @@
+# REQUIRES: x86
+# RUN: yaml2obj %s -o %t.o
+# RUN: not ld.lld %t.o -o %t.exe 2>&1 | FileCheck %s
+
+# The debug info has a broken relocation. Check that we don't crash
+# and still report the undefined symbol.
+
+# CHECK: error: undefined symbol: bar
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Content:         '0000000000000000'
+  - Name:            .rela.text
+    Type:            SHT_RELA
+    Link:            .symtab
+    Info:            .text
+    Relocations:
+      - Offset:          0x0000000000000000
+        Symbol:          bar
+        Type:            R_X86_64_64
+  - Name:            .debug_line
+    Type:            SHT_PROGBITS
+    Content:         3300000002001C0000000101FB0E0D000101010100000001000001006162632E7300000000000009020000000000000000140208000101
+  - Name:            .rela.debug_line
+    Type:            SHT_RELA
+    Link:            .symtab
+    Info:            .debug_line
+    Relocations:
+      - Offset:          0x0000000000000029
+        Symbol:          bar
+        Type:            R_X86_64_64
+Symbols:
+  Global:
+    - Name:            _start
+      Section:         .text
+    - Name:            bar