Index: lld/trunk/COFF/Driver.cpp
===================================================================
--- lld/trunk/COFF/Driver.cpp
+++ lld/trunk/COFF/Driver.cpp
@@ -18,6 +18,7 @@
 #include "lld/Common/Args.h"
 #include "lld/Common/Driver.h"
 #include "lld/Common/ErrorHandler.h"
+#include "lld/Common/Filesystem.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Threads.h"
 #include "lld/Common/Timer.h"
@@ -1525,6 +1526,12 @@
         getOutputPath((*Args.filtered(OPT_INPUT).begin())->getValue());
   }
 
+  // Fail early if an output file is not writable.
+  if (auto E = tryCreateFile(Config->OutputFile)) {
+    error("cannot open output file " + Config->OutputFile + ": " + E.message());
+    return;
+  }
+
   if (ShouldCreatePDB) {
     // Put the PDB next to the image if no /pdb flag was passed.
     if (Config->PDBPath.empty()) {
Index: lld/trunk/Common/CMakeLists.txt
===================================================================
--- lld/trunk/Common/CMakeLists.txt
+++ lld/trunk/Common/CMakeLists.txt
@@ -30,6 +30,7 @@
 add_lld_library(lldCommon
   Args.cpp
   ErrorHandler.cpp
+  Filesystem.cpp
   Memory.cpp
   Reproduce.cpp
   Strings.cpp
Index: lld/trunk/Common/Filesystem.cpp
===================================================================
--- lld/trunk/Common/Filesystem.cpp
+++ lld/trunk/Common/Filesystem.cpp
@@ -0,0 +1,99 @@
+//===- Filesystem.cpp -----------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains a few utility functions to handle files.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lld/Common/Filesystem.h"
+#include "lld/Common/Threads.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/Support/FileSystem.h"
+#if LLVM_ON_UNIX
+#include <unistd.h>
+#endif
+#include <thread>
+
+using namespace llvm;
+using namespace lld;
+
+// Removes a given file asynchronously. This is a performance hack,
+// so remove this when operating systems are improved.
+//
+// On Linux (and probably on other Unix-like systems), unlink(2) is a
+// noticeably slow system call. As of 2016, unlink takes 250
+// milliseconds to remove a 1 GB file on ext4 filesystem on my machine.
+//
+// To create a new result file, we first remove existing file. So, if
+// you repeatedly link a 1 GB program in a regular compile-link-debug
+// cycle, every cycle wastes 250 milliseconds only to remove a file.
+// Since LLD can link a 1 GB binary in about 5 seconds, that waste
+// actually counts.
+//
+// This function spawns a background thread to remove the file.
+// The calling thread returns almost immediately.
+void lld::unlinkAsync(StringRef Path) {
+// Removing a file is async on windows.
+#if defined(_WIN32)
+  sys::fs::remove(Path);
+#else
+  if (!ThreadsEnabled || !sys::fs::exists(Path) ||
+      !sys::fs::is_regular_file(Path))
+    return;
+
+  // We cannot just remove path from a different thread because we are now going
+  // to create path as a new file.
+  // Instead we open the file and unlink it on this thread. The unlink is fast
+  // since the open fd guarantees that it is not removing the last reference.
+  int FD;
+  std::error_code EC = sys::fs::openFileForRead(Path, FD);
+  sys::fs::remove(Path);
+
+  if (EC)
+    return;
+
+  // close and therefore remove TempPath in background.
+  std::mutex M;
+  std::condition_variable CV;
+  bool Started = false;
+  std::thread([&, FD] {
+    {
+      std::lock_guard<std::mutex> L(M);
+      Started = true;
+      CV.notify_all();
+    }
+    ::close(FD);
+  }).detach();
+
+  // GLIBC 2.26 and earlier have race condition that crashes an entire process
+  // if the main thread calls exit(2) while other thread is starting up.
+  std::unique_lock<std::mutex> L(M);
+  CV.wait(L, [&] { return Started; });
+#endif
+}
+
+// Simulate file creation to see if Path is writable.
+//
+// Determining whether a file is writable or not is amazingly hard,
+// and after all the only reliable way of doing that is to actually
+// create a file. But we don't want to do that in this function
+// because LLD shouldn't update any file if it will end in a failure.
+// We also don't want to reimplement heuristics to determine if a
+// file is writable. So we'll let FileOutputBuffer do the work.
+//
+// FileOutputBuffer doesn't touch a desitnation file until commit()
+// is called. We use that class without calling commit() to predict
+// if the given file is writable.
+std::error_code lld::tryCreateFile(StringRef Path) {
+  if (Path.empty())
+    return std::error_code();
+  if (Path == "-")
+    return std::error_code();
+  return errorToErrorCode(FileOutputBuffer::create(Path, 1).takeError());
+}
Index: lld/trunk/ELF/CMakeLists.txt
===================================================================
--- lld/trunk/ELF/CMakeLists.txt
+++ lld/trunk/ELF/CMakeLists.txt
@@ -27,7 +27,6 @@
   Driver.cpp
   DriverUtils.cpp
   EhFrame.cpp
-  Filesystem.cpp
   ICF.cpp
   InputFiles.cpp
   InputSection.cpp
Index: lld/trunk/ELF/Driver.cpp
===================================================================
--- lld/trunk/ELF/Driver.cpp
+++ lld/trunk/ELF/Driver.cpp
@@ -24,7 +24,6 @@
 
 #include "Driver.h"
 #include "Config.h"
-#include "Filesystem.h"
 #include "ICF.h"
 #include "InputFiles.h"
 #include "InputSection.h"
@@ -40,6 +39,7 @@
 #include "lld/Common/Args.h"
 #include "lld/Common/Driver.h"
 #include "lld/Common/ErrorHandler.h"
+#include "lld/Common/Filesystem.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Strings.h"
 #include "lld/Common/TargetOptionsCommandFlags.h"
Index: lld/trunk/ELF/Filesystem.h
===================================================================
--- lld/trunk/ELF/Filesystem.h
+++ lld/trunk/ELF/Filesystem.h
@@ -1,22 +0,0 @@
-//===- Filesystem.h ---------------------------------------------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLD_ELF_FILESYSTEM_H
-#define LLD_ELF_FILESYSTEM_H
-
-#include "lld/Common/LLVM.h"
-#include <system_error>
-
-namespace lld {
-namespace elf {
-void unlinkAsync(StringRef Path);
-std::error_code tryCreateFile(StringRef Path);
-} // namespace elf
-} // namespace lld
-
-#endif
Index: lld/trunk/ELF/Filesystem.cpp
===================================================================
--- lld/trunk/ELF/Filesystem.cpp
+++ lld/trunk/ELF/Filesystem.cpp
@@ -1,102 +0,0 @@
-//===- Filesystem.cpp -----------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file contains a few utility functions to handle files.
-//
-//===----------------------------------------------------------------------===//
-
-#include "Filesystem.h"
-#include "Config.h"
-#include "lld/Common/Threads.h"
-#include "llvm/Config/llvm-config.h"
-#include "llvm/Support/FileOutputBuffer.h"
-#include "llvm/Support/FileSystem.h"
-#if LLVM_ON_UNIX
-#include <unistd.h>
-#endif
-#include <thread>
-
-using namespace llvm;
-
-using namespace lld;
-using namespace lld::elf;
-
-// Removes a given file asynchronously. This is a performance hack,
-// so remove this when operating systems are improved.
-//
-// On Linux (and probably on other Unix-like systems), unlink(2) is a
-// noticeably slow system call. As of 2016, unlink takes 250
-// milliseconds to remove a 1 GB file on ext4 filesystem on my machine.
-//
-// To create a new result file, we first remove existing file. So, if
-// you repeatedly link a 1 GB program in a regular compile-link-debug
-// cycle, every cycle wastes 250 milliseconds only to remove a file.
-// Since LLD can link a 1 GB binary in about 5 seconds, that waste
-// actually counts.
-//
-// This function spawns a background thread to remove the file.
-// The calling thread returns almost immediately.
-void elf::unlinkAsync(StringRef Path) {
-// Removing a file is async on windows.
-#if defined(_WIN32)
-  sys::fs::remove(Path);
-#else
-  if (!ThreadsEnabled || !sys::fs::exists(Path) ||
-      !sys::fs::is_regular_file(Path))
-    return;
-
-  // We cannot just remove path from a different thread because we are now going
-  // to create path as a new file.
-  // Instead we open the file and unlink it on this thread. The unlink is fast
-  // since the open fd guarantees that it is not removing the last reference.
-  int FD;
-  std::error_code EC = sys::fs::openFileForRead(Path, FD);
-  sys::fs::remove(Path);
-
-  if (EC)
-    return;
-
-  // close and therefore remove TempPath in background.
-  std::mutex M;
-  std::condition_variable CV;
-  bool Started = false;
-  std::thread([&, FD] {
-    {
-      std::lock_guard<std::mutex> L(M);
-      Started = true;
-      CV.notify_all();
-    }
-    ::close(FD);
-  }).detach();
-
-  // GLIBC 2.26 and earlier have race condition that crashes an entire process
-  // if the main thread calls exit(2) while other thread is starting up.
-  std::unique_lock<std::mutex> L(M);
-  CV.wait(L, [&] { return Started; });
-#endif
-}
-
-// Simulate file creation to see if Path is writable.
-//
-// Determining whether a file is writable or not is amazingly hard,
-// and after all the only reliable way of doing that is to actually
-// create a file. But we don't want to do that in this function
-// because LLD shouldn't update any file if it will end in a failure.
-// We also don't want to reimplement heuristics to determine if a
-// file is writable. So we'll let FileOutputBuffer do the work.
-//
-// FileOutputBuffer doesn't touch a desitnation file until commit()
-// is called. We use that class without calling commit() to predict
-// if the given file is writable.
-std::error_code elf::tryCreateFile(StringRef Path) {
-  if (Path.empty())
-    return std::error_code();
-  if (Path == "-")
-    return std::error_code();
-  return errorToErrorCode(FileOutputBuffer::create(Path, 1).takeError());
-}
Index: lld/trunk/ELF/Writer.cpp
===================================================================
--- lld/trunk/ELF/Writer.cpp
+++ lld/trunk/ELF/Writer.cpp
@@ -10,7 +10,6 @@
 #include "AArch64ErrataFix.h"
 #include "CallGraphSort.h"
 #include "Config.h"
-#include "Filesystem.h"
 #include "LinkerScript.h"
 #include "MapFile.h"
 #include "OutputSections.h"
@@ -19,6 +18,7 @@
 #include "Symbols.h"
 #include "SyntheticSections.h"
 #include "Target.h"
+#include "lld/Common/Filesystem.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Strings.h"
 #include "lld/Common/Threads.h"
Index: lld/trunk/include/lld/Common/Filesystem.h
===================================================================
--- lld/trunk/include/lld/Common/Filesystem.h
+++ lld/trunk/include/lld/Common/Filesystem.h
@@ -0,0 +1,20 @@
+//===- Filesystem.h ---------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_FILESYSTEM_H
+#define LLD_FILESYSTEM_H
+
+#include "lld/Common/LLVM.h"
+#include <system_error>
+
+namespace lld {
+void unlinkAsync(StringRef Path);
+std::error_code tryCreateFile(StringRef Path);
+} // namespace lld
+
+#endif
Index: lld/trunk/test/COFF/driver.test
===================================================================
--- lld/trunk/test/COFF/driver.test
+++ lld/trunk/test/COFF/driver.test
@@ -15,3 +15,7 @@
 
 # RUN: not lld-link /WX /lib 2>&1 | FileCheck -check-prefix=LIBBAD %s
 LIBBAD: ignoring /lib since it's not the first argument
+
+# RUN: yaml2obj < %p/Inputs/hello32.yaml > %t.obj
+# RUN: not lld-link /out:/ %t.obj 2>&1 | FileCheck -check-prefix=DIR %s
+DIR: cannot open output file