Index: lib/Support/raw_ostream.cpp
===================================================================
--- lib/Support/raw_ostream.cpp
+++ lib/Support/raw_ostream.cpp
@@ -473,7 +473,7 @@
     // possible.
     if (!(Flags & sys::fs::F_Text))
       sys::ChangeStdoutToBinary();
-    return STDOUT_FILENO;
+    return dup(STDOUT_FILENO);
   }
 
   int FD;
Index: test/Other/writing-to-stdout.ll
===================================================================
--- test/Other/writing-to-stdout.ll
+++ test/Other/writing-to-stdout.ll
@@ -0,0 +1,14 @@
+; Often LLVM tools use "-" to indicate that output should be written to stdout
+; instead of a file. This behaviour is implemented by the raw_fd_ostream class.
+; This test verifies that when doing so multiple times we don't try to access a
+; closed STDOUT_FILENO. The exact options used in this test are unimportant, as
+; long as they write to stdout using raw_fd_ostream.
+; RUN: llc %s -o=- -pass-remarks-output=- -filetype=asm | FileCheck %s
+; foobar should appear as a function somewhere in the assembly file.
+; CHECK: foobar
+; !Analysis appears at the start of pass-remarks-output.
+; CHECK: !Analysis
+
+define void @foobar() {
+  ret void
+}
Index: unittests/Support/raw_ostream_test.cpp
===================================================================
--- unittests/Support/raw_ostream_test.cpp
+++ unittests/Support/raw_ostream_test.cpp
@@ -9,6 +9,7 @@
 
 #include "gtest/gtest.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -330,4 +331,11 @@
             "0007: 68 69 6a 6b 6c        |hijkl|",
             format_bytes_with_ascii_str(B.take_front(12), 0, 7, 1));
 }
+
+TEST(raw_fd_ostreamTest, multiple_raw_fd_ostream_to_stdout) {
+  std::error_code EC;
+
+  { raw_fd_ostream("-", EC, sys::fs::OpenFlags::F_None); }
+  { raw_fd_ostream("-", EC, sys::fs::OpenFlags::F_None); }
+}
 }