Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -43,7 +43,7 @@
 private:
   void copyLocalSymbols();
   void addReservedSymbols();
-  void createSections();
+  bool createSections();
   void addPredefinedSections();
 
   template <bool isRela>
@@ -156,7 +156,8 @@
   if (!Config->DiscardAll)
     copyLocalSymbols();
   addReservedSymbols();
-  createSections();
+  if (!createSections())
+    return;
   assignAddresses();
   fixAbsoluteSymbols();
   openFile(Config->OutputFile);
@@ -382,7 +383,7 @@
   if (Config->NoInhibitExec)
     warning(Msg);
   else
-    fatal(Msg);
+    error(Msg);
 }
 
 template <class ELFT>
@@ -796,7 +797,7 @@
 }
 
 // Create output section objects and add them to OutputSections.
-template <class ELFT> void Writer<ELFT>::createSections() {
+template <class ELFT> bool Writer<ELFT>::createSections() {
   // Add .interp first because some loaders want to see that section
   // on the first page of the executable file when loaded into memory.
   if (needsInterpSection())
@@ -887,6 +888,11 @@
     if (isOutputDynamic() && includeInDynamicSymtab(*Body))
       Out<ELFT>::DynSymTab->addSymbol(Body);
   }
+
+  // Do not proceed if there was an undefined symbol.
+  if (HasError)
+    return false;
+
   addCommonSymbols(CommonSymbols);
   addCopyRelSymbols(CopyRelSymbols);
 
@@ -915,6 +921,7 @@
   for (OutputSectionBase<ELFT> *Sec : OutputSections)
     if (Sec != Out<ELFT>::DynStrTab)
       Sec->finalize();
+  return true;
 }
 
 // This function add Out<ELFT>::* sections to OutputSections.
Index: test/ELF/undef.s
===================================================================
--- test/ELF/undef.s
+++ test/ELF/undef.s
@@ -1,8 +1,10 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: not ld.lld %t -o %t2 2>&1 | FileCheck %s
+# CHECK: undefined symbol: bar in {{.*}}
 # CHECK: undefined symbol: foo in {{.*}}
 # REQUIRES: x86
 
-  .globl _start;
+  .globl _start
 _start:
   call foo
+  call bar