[ELF] Prevent SEGFAULT in case of conflict with an internally defined symbol.

Differential Revision: http://reviews.llvm.org/D14832

llvm-svn: 253588

lld/ELF/SymbolTable.cpp

@@ -139,7 +139,8 @@ void SymbolTable<ELFT>::reportConflict(const Twine &Message,
   }
 
   std::string Msg = (Message + ": " + Old.getName() + " in " +
-                     OldFile->getName() + " and " + NewFile->getName())
+                     (OldFile ? OldFile->getName() : "(internal)") + " and " +
+                     (NewFile ? NewFile->getName() : "(internal)"))
                         .str();
   if (Warning)
     warning(Msg);

lld/test/ELF/duplicate-internal.s

@@ -0,0 +1,11 @@
+# Should print an expected message in case of conflict with an internally generated symbol.
+
+# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t.o
+# RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
+
+# CHECK: duplicate symbol: _gp in (internal) and {{.*}}
+
+# REQUIRES: mips
+
+  .globl  _gp
+_gp = 0