Index: lld/trunk/COFF/SymbolTable.cpp
===================================================================
--- lld/trunk/COFF/SymbolTable.cpp
+++ lld/trunk/COFF/SymbolTable.cpp
@@ -123,7 +123,7 @@
 }
 
 bool SymbolTable::reportRemainingUndefines(bool Resolve) {
-  bool Ret = false;
+  llvm::SmallPtrSet<SymbolBody *, 8> Undefs;
   for (auto &I : Symtab) {
     Symbol *Sym = I.second;
     auto *Undef = dyn_cast<Undefined>(Sym->Body);
@@ -150,17 +150,24 @@
         continue;
       }
     }
-    llvm::errs() << "undefined symbol: " << Name << "\n";
     // Remaining undefined symbols are not fatal if /force is specified.
     // They are replaced with dummy defined symbols.
-    if (Config->Force) {
-      if (Resolve)
-        Sym->Body = new (Alloc) DefinedAbsolute(Name, 0);
-      continue;
-    }
-    Ret = true;
-  }
-  return Ret;
+    if (Config->Force && Resolve)
+      Sym->Body = new (Alloc) DefinedAbsolute(Name, 0);
+    Undefs.insert(Sym->Body);
+  }
+  if (Undefs.empty())
+    return false;
+  for (Undefined *U : Config->GCRoot)
+    if (Undefs.count(U->repl()))
+      llvm::errs() << "<root>: undefined symbol: " << U->getName() << "\n";
+  for (std::unique_ptr<InputFile> &File : Files)
+    if (!isa<ArchiveFile>(File.get()))
+      for (SymbolBody *Sym : File->getSymbols())
+        if (Undefs.count(Sym->repl()))
+          llvm::errs() << File->getShortName() << ": undefined symbol: "
+                       << Sym->getName() << "\n";
+  return !Config->Force;
 }
 
 void SymbolTable::addLazy(Lazy *New, std::vector<Symbol *> *Accum) {
Index: lld/trunk/test/COFF/entry-inference.test
===================================================================
--- lld/trunk/test/COFF/entry-inference.test
+++ lld/trunk/test/COFF/entry-inference.test
@@ -14,10 +14,10 @@
 # RUN: not lld -flavor link2 /out:%t.exe %t.obj > %t.log 2>&1
 # RUN: FileCheck -check-prefix=WWINMAIN %s < %t.log
 
-# MAIN:     undefined symbol: mainCRTStartup
-# WMAIN:    undefined symbol: wmainCRTStartup
-# WINMAIN:  undefined symbol: WinMainCRTStartup
-# WWINMAIN: undefined symbol: wWinMainCRTStartup
+# MAIN:     <root>: undefined symbol: mainCRTStartup
+# WMAIN:    <root>: undefined symbol: wmainCRTStartup
+# WINMAIN:  <root>: undefined symbol: WinMainCRTStartup
+# WWINMAIN: <root>: undefined symbol: wWinMainCRTStartup
 
 ---
 header:
Index: lld/trunk/test/COFF/force.test
===================================================================
--- lld/trunk/test/COFF/force.test
+++ lld/trunk/test/COFF/force.test
@@ -4,7 +4,7 @@
 # RUN: lld -flavor link2 /out:%t.exe /entry:main %t.obj /force >& %t.log
 # RUN: FileCheck %s < %t.log
 
-# CHECK: undefined symbol: foo
+# CHECK: .obj: undefined symbol: foo
 
 ---
 header:
Index: lld/trunk/test/COFF/nodefaultlib.test
===================================================================
--- lld/trunk/test/COFF/nodefaultlib.test
+++ lld/trunk/test/COFF/nodefaultlib.test
@@ -21,7 +21,7 @@
 
 CHECK1: hello64.obj: {{[Nn]}}o such file or directory
 CHECK2: hello64: {{[Nn]}}o such file or directory
-CHECK3: undefined symbol: MessageBoxA
+CHECK3: hello64.obj: undefined symbol: MessageBoxA
 
 # RUN: lld -flavor link2 /libpath:%T /out:%t.exe /entry:main \
 # RUN:   /subsystem:console hello64.obj /defaultlib:std64.lib