Index: COFF/Chunks.cpp
===================================================================
--- COFF/Chunks.cpp
+++ COFF/Chunks.cpp
@@ -10,7 +10,6 @@
 #include "Chunks.h"
 #include "InputFiles.h"
 #include "Writer.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/COFF.h"
Index: COFF/Driver.cpp
===================================================================
--- COFF/Driver.cpp
+++ COFF/Driver.cpp
@@ -13,7 +13,6 @@
 #include "Memory.h"
 #include "SymbolTable.h"
 #include "Writer.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Option/Arg.h"
Index: COFF/DriverUtils.cpp
===================================================================
--- COFF/DriverUtils.cpp
+++ COFF/DriverUtils.cpp
@@ -14,8 +14,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "Driver.h"
+#include "Error.h"
 #include "Memory.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -24,7 +24,6 @@
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Format.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/raw_ostream.h"
@@ -114,8 +113,10 @@
                           .Case("x64", IMAGE_FILE_MACHINE_AMD64)
                           .Case("x86", IMAGE_FILE_MACHINE_I386)
                           .Default(IMAGE_FILE_MACHINE_UNKNOWN);
-    if (MT == IMAGE_FILE_MACHINE_UNKNOWN)
-      return make_dynamic_error_code("unknown /machine argument" + S);
+    if (MT == IMAGE_FILE_MACHINE_UNKNOWN) {
+      llvm::errs() << "unknown /machine argument" << S << "\n";
+      return make_error_code(DriverError::InvalidOption);
+    }
     return MT;
   }
   // If /machine option is missing, we need to take a look at
@@ -132,10 +133,14 @@
 std::error_code parseNumbers(StringRef Arg, uint64_t *Addr, uint64_t *Size) {
   StringRef S1, S2;
   std::tie(S1, S2) = Arg.split(',');
-  if (S1.getAsInteger(0, *Addr))
-    return make_dynamic_error_code(Twine("invalid number: ") + S1);
-  if (Size && !S2.empty() && S2.getAsInteger(0, *Size))
-    return make_dynamic_error_code(Twine("invalid number: ") + S2);
+  if (S1.getAsInteger(0, *Addr)) {
+    llvm::errs() << "invalid number: " << S1 << "\n";
+    return make_error_code(DriverError::InvalidOption);
+  }
+  if (Size && !S2.empty() && S2.getAsInteger(0, *Size)) {
+    llvm::errs() << "invalid number: " << S2 << "\n";
+    return make_error_code(DriverError::InvalidOption);
+  }
   return std::error_code();
 }
 
@@ -144,11 +149,15 @@
 std::error_code parseVersion(StringRef Arg, uint32_t *Major, uint32_t *Minor) {
   StringRef S1, S2;
   std::tie(S1, S2) = Arg.split('.');
-  if (S1.getAsInteger(0, *Major))
-    return make_dynamic_error_code(Twine("invalid number: ") + S1);
+  if (S1.getAsInteger(0, *Major)) {
+    llvm::errs() << "invalid number: " << S1 << "\n";
+    return make_error_code(DriverError::InvalidOption);
+  }
   *Minor = 0;
-  if (!S2.empty() && S2.getAsInteger(0, *Minor))
-    return make_dynamic_error_code(Twine("invalid number: ") + S2);
+  if (!S2.empty() && S2.getAsInteger(0, *Minor)) {
+    llvm::errs() << "invalid number: " << S2 << "\n";
+    return make_error_code(DriverError::InvalidOption);
+  }
   return std::error_code();
 }
 
@@ -168,8 +177,10 @@
     .Case("posix", IMAGE_SUBSYSTEM_POSIX_CUI)
     .Case("windows", IMAGE_SUBSYSTEM_WINDOWS_GUI)
     .Default(IMAGE_SUBSYSTEM_UNKNOWN);
-  if (*Sys == IMAGE_SUBSYSTEM_UNKNOWN)
-    return make_dynamic_error_code(Twine("unknown subsystem: ") + SysStr);
+  if (*Sys == IMAGE_SUBSYSTEM_UNKNOWN) {
+    llvm::errs() << "unknown subsystem: " << SysStr << "\n";
+    return make_error_code(DriverError::InvalidOption);
+  }
   if (!Ver.empty())
     if (auto EC = parseVersion(Ver, Major, Minor))
       return EC;
@@ -207,13 +218,11 @@
   std::unique_ptr<llvm::opt::InputArgList> Args(
       Table.ParseArgs(&Argv[1], &Argv[Argc], MissingIndex, MissingCount));
   if (MissingCount) {
-    std::string S;
-    llvm::raw_string_ostream OS(S);
-    OS << llvm::format("missing arg value for \"%s\", expected %d argument%s.",
-                       Args->getArgString(MissingIndex), MissingCount,
-                       (MissingCount == 1 ? "" : "s"));
-    OS.flush();
-    return make_dynamic_error_code(StringRef(S));
+    llvm::errs() << "missing arg value for \""
+                 << Args->getArgString(MissingIndex)
+                 << "\", expected " << MissingCount
+                 << (MissingCount == 1 ? " argument.\n" : " arguments.\n");
+    return make_error_code(DriverError::InvalidOption);
   }
   for (auto *Arg : Args->filtered(OPT_UNKNOWN))
     llvm::errs() << "ignoring unknown argument: " << Arg->getSpelling() << "\n";
Index: COFF/Error.h
===================================================================
--- /dev/null
+++ COFF/Error.h
@@ -0,0 +1,94 @@
+//===- Error.h ------------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_COFF_ERROR_H
+#define LLD_COFF_ERROR_H
+
+#include <string>
+#include <system_error>
+#include "llvm/Support/ErrorHandling.h"
+
+namespace lld {
+namespace coff {
+
+// Driver errors
+enum class DriverError { Success, InvalidOption };
+
+class DriverErrorCategory : public std::error_category {
+public:
+  const char *name() const override { return "lld.driver"; }
+
+  std::string message(int EV) const override {
+    switch (static_cast<int>(EV)) {
+    case DriverError::Success:
+      return "Success";
+    case DriverError::InvalidOption:
+      return "Invalid option";
+    }
+    llvm_unreachable("unknown error");
+  }
+};
+
+inline std::error_code make_error_code(DriverError Err) {
+  static DriverErrorCategory C;
+  return std::error_code(static_cast<int>(Err), C);
+}
+
+// InputFile errors
+enum class ReaderError { Success, InvalidFile, BrokenFile };
+
+class ReaderErrorCategory : public std::error_category {
+public:
+  const char *name() const override { return "lld.reader"; }
+
+  std::string message(int EV) const override {
+    switch (static_cast<int>(EV)) {
+    case ReaderError::Success:
+      return "Success";
+    case ReaderError::InvalidFile:
+      return "Invalid file";
+    case ReaderError::BrokenFile:
+      return "broken file";
+    }
+    llvm_unreachable("unknown error");
+  }
+};
+
+inline std::error_code make_error_code(ReaderError Err) {
+  static ReaderErrorCategory C;
+  return std::error_code(static_cast<int>(Err), C);
+}
+
+// SymbolTable errors
+enum class SymbolError { Success, Duplicate };
+
+class SymbolErrorCategory : public std::error_category {
+public:
+  const char *name() const override { return "lld.symbol"; }
+
+  std::string message(int EV) const override {
+    switch (static_cast<int>(EV)) {
+    case SymbolError::Success:
+      return "Success";
+    case SymbolError::Duplicate:
+      return "Duplicate symbols";
+    }
+    llvm_unreachable("unknown error");
+  }
+};
+
+inline std::error_code make_error_code(SymbolError Err) {
+  static SymbolErrorCategory C;
+  return std::error_code(static_cast<int>(Err), C);
+}
+
+} // namespace coff
+} // namespace lld
+
+#endif
Index: COFF/InputFiles.cpp
===================================================================
--- COFF/InputFiles.cpp
+++ COFF/InputFiles.cpp
@@ -8,9 +8,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "Chunks.h"
+#include "Error.h"
 #include "InputFiles.h"
 #include "Writer.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/COFF.h"
@@ -108,7 +108,8 @@
     Bin.release();
     COFFObj.reset(Obj);
   } else {
-    return make_dynamic_error_code(Twine(Filename) + " is not a COFF file.");
+    llvm::errs() << Filename << " is not a COFF file.\n";
+    return make_error_code(ReaderError::InvalidFile);
   }
 
   // Read section and symbol tables.
@@ -128,12 +129,16 @@
   for (uint32_t I = 1; I < NumSections + 1; ++I) {
     const coff_section *Sec;
     StringRef Name;
-    if (auto EC = COFFObj->getSection(I, Sec))
-      return make_dynamic_error_code(Twine("getSection failed: ") + Name +
-                                     ": " + EC.message());
-    if (auto EC = COFFObj->getSectionName(Sec, Name))
-      return make_dynamic_error_code(Twine("getSectionName failed: ") + Name +
-                                     ": " + EC.message());
+    if (auto EC = COFFObj->getSection(I, Sec)) {
+      llvm::errs() << "getSection failed: " << Name << ": "
+                   << EC.message() << "\n";
+      return make_error_code(ReaderError::BrokenFile);
+    }
+    if (auto EC = COFFObj->getSectionName(Sec, Name)) {
+      llvm::errs() << "getSectionName failed: " << Name << ": "
+                   << EC.message() << "\n";
+      return make_error_code(ReaderError::BrokenFile);
+    }
     if (Name == ".drectve") {
       ArrayRef<uint8_t> Data;
       COFFObj->getSectionContents(Sec, Data);
@@ -159,16 +164,20 @@
   for (uint32_t I = 0; I < NumSymbols; ++I) {
     // Get a COFFSymbolRef object.
     auto SymOrErr = COFFObj->getSymbol(I);
-    if (auto EC = SymOrErr.getError())
-      return make_dynamic_error_code(Twine("broken object file: ") + Filename +
-                                     ": " + EC.message());
+    if (auto EC = SymOrErr.getError()) {
+      llvm::dbgs() << "broken object file: " << Filename << ": "
+                   << EC.message() << "\n";
+      return make_error_code(ReaderError::BrokenFile);
+    }
     COFFSymbolRef Sym = SymOrErr.get();
 
     // Get a symbol name.
     StringRef SymbolName;
-    if (auto EC = COFFObj->getSymbolName(Sym, SymbolName))
-      return make_dynamic_error_code(Twine("broken object file: ") + Filename +
-                                     ": " + EC.message());
+    if (auto EC = COFFObj->getSymbolName(Sym, SymbolName)) {
+      llvm::dbgs() << "broken object file: " << Filename << ": "
+                   << EC.message() << "\n";
+      return make_error_code(ReaderError::BrokenFile);
+    }
     // Skip special symbols.
     if (SymbolName == "@comp.id" || SymbolName == "@feat.00")
       continue;
@@ -225,8 +234,10 @@
   const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);
 
   // Check if the total size is valid.
-  if (End - Buf != sizeof(*Hdr) + Hdr->SizeOfData)
-    return make_dynamic_error_code("broken import library");
+  if (End - Buf != sizeof(*Hdr) + Hdr->SizeOfData) {
+    llvm::errs() << "broken import library\n";
+    return make_error_code(ReaderError::BrokenFile);
+  }
 
   // Read names and create an __imp_ symbol.
   StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr)));
Index: COFF/SymbolTable.cpp
===================================================================
--- COFF/SymbolTable.cpp
+++ COFF/SymbolTable.cpp
@@ -9,8 +9,8 @@
 
 #include "Config.h"
 #include "Driver.h"
+#include "Error.h"
 #include "SymbolTable.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -117,8 +117,10 @@
   int comp = Existing->compare(New);
   if (comp < 0)
     Sym->Body = New;
-  if (comp == 0)
-    return make_dynamic_error_code(Twine("duplicate symbol: ") + Name);
+  if (comp == 0) {
+    llvm::dbgs() << "duplicate symbol: " << Name << "\n";
+    return make_error_code(SymbolError::Duplicate);
+  }
 
   // If we have an Undefined symbol for a Lazy symbol, we need
   // to read an archive member to replace the Lazy symbol with
Index: COFF/Symbols.cpp
===================================================================
--- COFF/Symbols.cpp
+++ COFF/Symbols.cpp
@@ -7,9 +7,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "Error.h"
 #include "InputFiles.h"
 #include "Symbols.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -84,8 +84,10 @@
   if (Magic == file_magic::coff_import_library)
     return std::unique_ptr<InputFile>(new ImportFile(MBRef));
 
-  if (Magic != file_magic::coff_object)
-    return make_dynamic_error_code("unknown file type");
+  if (Magic != file_magic::coff_object) {
+    llvm::dbgs() << File->getName() << ": unknown file type\n";
+    return make_error_code(ReaderError::InvalidFile);
+  }
 
   std::unique_ptr<InputFile> Obj(new ObjectFile(MBRef.getBufferIdentifier(), MBRef));
   Obj->setParentName(File->getName());
Index: COFF/Writer.cpp
===================================================================
--- COFF/Writer.cpp
+++ COFF/Writer.cpp
@@ -9,7 +9,6 @@
 
 #include "Config.h"
 #include "Writer.h"
-#include "lld/Core/Error.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/STLExtras.h"
@@ -300,9 +299,10 @@
 
 std::error_code Writer::openFile(StringRef Path) {
   if (auto EC = FileOutputBuffer::create(Path, FileSize, Buffer,
-                                         FileOutputBuffer::F_executable))
-    return make_dynamic_error_code(Twine("Failed to open ") + Path + ": " +
-                                   EC.message());
+                                         FileOutputBuffer::F_executable)) {
+    llvm::errs() << "failed to open " << Path << ": " << EC.message() << "\n";
+    return EC;
+  }
   return std::error_code();
 }