--- gcc/diagnostic-color.c	2015-01-05 13:33:28.000000000 +0100
+++ gcc/diagnostic-color.c	2016-03-05 12:57:08.156905200 +0100
@@ -264,12 +264,61 @@
 }
 
 #if defined(_WIN32)
-bool
-colorize_init (diagnostic_color_rule_t)
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <winternl.h>
+
+#ifndef ENABLE_VIRTUAL_TERMINAL_PROCESSING
+#define ENABLE_VIRTUAL_TERMINAL_PROCESSING 0x0004
+#endif
+
+static int
+w_isatty (int num)
 {
-  return false;
+  HANDLE fh = (HANDLE)_get_osfhandle (num);
+  if (fh == INVALID_HANDLE_VALUE)
+    return 0;
+
+  DWORD flags;
+  if (GetConsoleMode (fh, &flags))
+    /* Check if console understands terminal escape sequences.  */
+    return SetConsoleMode (fh, flags | ENABLE_VIRTUAL_TERMINAL_PROCESSING);
+
+  HMODULE ntdll = GetModuleHandle ("ntdll.dll");
+  if (!ntdll)
+    return 0;
+
+  typedef NTSTATUS NTAPI func_NtQueryObject (HANDLE, OBJECT_INFORMATION_CLASS,
+					     PVOID, ULONG, PULONG);
+  func_NtQueryObject *fNtQueryObject =
+    (func_NtQueryObject*) GetProcAddress (ntdll, "NtQueryObject");
+  if (!fNtQueryObject)
+    return 0;
+
+  ULONG s = 0xffff * sizeof (WCHAR);
+  OBJECT_NAME_INFORMATION *oni = (OBJECT_NAME_INFORMATION*) xmalloc (s);
+  ULONG len;
+  int is_a_tty = 0;
+  /* mintty uses a named pipe like "ptyNNNN-to-master".  */
+  if (!fNtQueryObject (fh, ObjectNameInformation, oni, s, &len))
+    {
+      wchar_t namedPipe[] = L"\\Device\\NamedPipe\\";
+      size_t l1 = sizeof (namedPipe) / 2 - 1;
+      wchar_t toMaster[] = L"-to-master";
+      size_t l2 = sizeof (toMaster) / 2 - 1;
+      USHORT name_length = oni->Name.Length / 2;
+      if (name_length > l1 + l2 &&
+	  !memcmp (oni->Name.Buffer, namedPipe, l1 * 2) &&
+	  !memcmp (oni->Name.Buffer + (name_length - l2), toMaster, l2 * 2))
+	is_a_tty = 1;
+    }
+
+  free (oni);
+
+  return is_a_tty;
 }
-#else
+#define isatty w_isatty
+#endif
 
 /* Return true if we should use color when in auto mode, false otherwise. */
 static bool
@@ -298,4 +347,3 @@
       gcc_unreachable ();
     }
 }
-#endif