diff --git a/gcc/ada/adaint.c b/gcc/ada/adaint.c
index bff875a6822..fc06ee7b663 100644
--- a/gcc/ada/adaint.c
+++ b/gcc/ada/adaint.c
@@ -549,7 +549,11 @@ __gnat_try_lock (char *dir, char *file)
 int
 __gnat_get_maximum_file_name_length (void)
 {
+#if defined (__DJGPP__)
+  return (_use_lfn(".")) ? -1 : 8;
+#else
   return -1;
+#endif
 }
 
 /* Return nonzero if file names are case sensitive.  */
@@ -623,6 +627,17 @@ __gnat_get_current_dir (char *dir, int *length)
        dir [*length] = DIR_SEPARATOR;
        ++(*length);
      }
+#ifdef __DJGPP__
+   do {
+     char *w;
+     for (w = dir; *w; ++w)
+       {
+	 if (*w == '/') {
+	   *w = '\\';
+	 }
+       }
+   } while (0);
+#endif /* __DJGPP__ */
    dir[*length] = '\0';
 }
 
diff --git a/gcc/ada/s-os_lib.adb b/gcc/ada/s-os_lib.adb
index 36064e97bd3..18bfb484074 100644
--- a/gcc/ada/s-os_lib.adb
+++ b/gcc/ada/s-os_lib.adb
@@ -71,7 +71,7 @@ package body System.OS_Lib is
 
    --  The following are used by Create_Temp_File
 
-   First_Temp_File_Name : constant String := "GNAT-TEMP-000000.TMP";
+   First_Temp_File_Name : constant String := "GA000000.TMP";
    --  Used to initialize Current_Temp_File_Name and Temp_File_Name_Last_Digit
 
    Current_Temp_File_Name : String := First_Temp_File_Name;
diff --git a/gcc/ginclude/float.h b/gcc/ginclude/float.h
index 658017fd63a..e6504b94d07 100644
--- a/gcc/ginclude/float.h
+++ b/gcc/ginclude/float.h
@@ -25,6 +25,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  * ISO C Standard:  5.2.4.2.2  Characteristics of floating types <float.h>
  */
 
+#ifdef __DJGPP__
+#include_next <float.h>
+#endif
+
 #ifndef _FLOAT_H___
 #define _FLOAT_H___
 
diff --git a/include/libiberty.h b/include/libiberty.h
index 7a796124bf5..0eb73f6650b 100644
--- a/include/libiberty.h
+++ b/include/libiberty.h
@@ -108,6 +108,7 @@ extern int countargv (char * const *);
 #if defined (__GNU_LIBRARY__ ) || defined (__linux__) \
  || defined (__FreeBSD__) || defined (__OpenBSD__) || defined (__NetBSD__) \
  || defined (__CYGWIN__) || defined (__CYGWIN32__) || defined (__MINGW32__) \
+ || defined (__DJGPP__) \
  || defined (__DragonFly__) || defined (HAVE_DECL_BASENAME) 
 extern char *basename (const char *) ATTRIBUTE_RETURNS_NONNULL ATTRIBUTE_NONNULL(1);
 #else
diff --git a/libcpp/files.c b/libcpp/files.c
index 969a531033f..3c07d60a62c 100644
--- a/libcpp/files.c
+++ b/libcpp/files.c
@@ -740,6 +740,10 @@ read_file_guts (cpp_reader *pfile, _cpp_file *file, source_location loc)
     cpp_error_at (pfile, CPP_DL_WARNING, loc,
 	       "%s is shorter than expected", file->path);
 
+/* For DOS we should handle DOS EOF character (0x1A, ^Z). It is
+   only done if it is really the last character of the file  */
+  if (total>0 && buf[total-1]==0x1A) total--;
+
   file->buffer = _cpp_convert_input (pfile,
 				     CPP_OPTION (pfile, input_charset),
 				     buf, size + 16, total,
diff --git a/libgfortran/intrinsics/chmod.c b/libgfortran/intrinsics/chmod.c
index d08418d773f..109e15ff3ab 100644
--- a/libgfortran/intrinsics/chmod.c
+++ b/libgfortran/intrinsics/chmod.c
@@ -443,7 +443,7 @@ clause_done:
 	if ((ugo[2] || honor_umask) && !rwxXstugo[8])
 	  file_mode = (file_mode & ~(S_IROTH | S_IWOTH | S_IXOTH))
 		      | (new_mode & (S_IROTH | S_IWOTH | S_IXOTH));
-#ifndef __VXWORKS__
+#if !defined(__VXWORKS__) && !defined(__DJGPP__)
 	if (is_dir && rwxXstugo[5])
 	  file_mode |= S_ISVTX;
 	else if (!is_dir)
@@ -455,7 +455,7 @@ clause_done:
       {
 	/* Clear '-'.  */
 	file_mode &= ~new_mode;
-#if !defined( __MINGW32__) && !defined (__VXWORKS__)
+#if !defined( __MINGW32__) && !defined (__VXWORKS__) && !defined(__DJGPP__)
 	if (rwxXstugo[5] || !is_dir)
 	  file_mode &= ~S_ISVTX;
 #endif
@@ -463,7 +463,7 @@ clause_done:
     else if (set_mode == 3)
       {
 	file_mode |= new_mode;
-#if !defined (__MINGW32__) && !defined (__VXWORKS__)
+#if !defined (__MINGW32__) && !defined (__VXWORKS__) && !defined(__DJGPP__)
 	if (rwxXstugo[5] && is_dir)
 	  file_mode |= S_ISVTX;
 	else if (!is_dir)
diff --git a/libgfortran/io/unix.c b/libgfortran/io/unix.c
index bb9bc9a5c12..79d25e1ebe0 100644
--- a/libgfortran/io/unix.c
+++ b/libgfortran/io/unix.c
@@ -210,6 +210,9 @@ typedef struct
 }
 unix_stream;
 
+#ifdef __DJGPP__
+#include <io.h>
+#endif
 
 /* fix_fd()-- Given a file descriptor, make sure it is not one of the
    standard descriptors, returning a non-standard descriptor.  If the
@@ -1187,8 +1190,13 @@ tempfile_open (const char *tempdir, char **fname)
   char *template = xmalloc (tempdirlen + 23);
 
 #ifdef HAVE_MKSTEMP
+#ifdef __DJGPP__
+  /* Default filename is too long for DOS */
+  snprintf (template, tempdirlen + 23, "%s/gfXXXXXX", tempdir);
+#else
   snprintf (template, tempdirlen + 23, "%s%sgfortrantmpXXXXXX", 
 	    tempdir, slash);
+#endif
 
 #ifdef HAVE_UMASK
   /* Temporarily set the umask such that the file has 0600 permissions.  */
@@ -1554,6 +1562,13 @@ open_external (st_parameter_open *opp, unit_flags *flags)
     return NULL;
   fd = fix_fd (fd);
 
+#ifdef __DJGPP__
+  if (flags->form == FORM_UNFORMATTED)
+    {
+      setmode (fd, O_BINARY);
+    }
+#endif
+
   if (open_share (opp, fd, flags) < 0)
     return NULL;
 
diff --git a/libiberty/make-relative-prefix.c b/libiberty/make-relative-prefix.c
index f74bbdc9038..4b2020e55b6 100644
--- a/libiberty/make-relative-prefix.c
+++ b/libiberty/make-relative-prefix.c
@@ -65,6 +65,7 @@ relative prefix can be found, return @code{NULL}.
 
 #include "ansidecl.h"
 #include "libiberty.h"
+#include "filenames.h"
 
 #ifndef R_OK
 #define R_OK 4
@@ -337,7 +338,7 @@ make_relative_prefix_1 (const char *progname, const char *bin_prefix,
     {
       for (i = 0; i < bin_num; i++)
 	{
-	  if (strcmp (prog_dirs[i], bin_dirs[i]) != 0)
+	  if (FILENAME_CMP (prog_dirs[i], bin_dirs[i]) != 0)
 	    break;
 	}
 
@@ -353,7 +354,7 @@ make_relative_prefix_1 (const char *progname, const char *bin_prefix,
   n = (prefix_num < bin_num) ? prefix_num : bin_num;
   for (common = 0; common < n; common++)
     {
-      if (strcmp (bin_dirs[common], prefix_dirs[common]) != 0)
+      if (FILENAME_CMP (bin_dirs[common], prefix_dirs[common]) != 0)
 	break;
     }
 
diff --git a/libiberty/make-temp-file.c b/libiberty/make-temp-file.c
index 98e215d15e7..1c2defad7b1 100644
--- a/libiberty/make-temp-file.c
+++ b/libiberty/make-temp-file.c
@@ -47,6 +47,7 @@ Boston, MA 02110-1301, USA.  */
 #endif
 
 #include "libiberty.h"
+#include "filenames.h"
 extern int mkstemps (char *, int);
 
 /* '/' works just fine on MS-DOS based systems.  */
@@ -142,7 +143,8 @@ choose_tmpdir (void)
       len = strlen (base);
       tmpdir = XNEWVEC (char, len + 2);
       strcpy (tmpdir, base);
-      tmpdir[len] = DIR_SEPARATOR;
+      if (len>0 && !IS_DIR_SEPARATOR(tmpdir[len-1]))
+          tmpdir[len] = DIR_SEPARATOR;
       tmpdir[len+1] = '\0';
       memoized_tmpdir = tmpdir;
 #else /* defined(_WIN32) && !defined(__CYGWIN__) */
diff --git a/libquadmath/printf/quadmath-printf.h b/libquadmath/printf/quadmath-printf.h
index 32ebcec928c..96498b7c408 100644
--- a/libquadmath/printf/quadmath-printf.h
+++ b/libquadmath/printf/quadmath-printf.h
@@ -29,7 +29,8 @@ Boston, MA 02110-1301, USA.  */
 #ifdef HAVE_CTYPE_H
 #include <ctype.h>
 #endif
-#ifdef HAVE_WCHAR_H
+#if defined(HAVE_WCHAR_H) && !defined(__DJGPP__)
+/* DJGPP wchar.h is not good enough */
 #include <wchar.h>
 #endif
 #ifdef HAVE_WCTYPE_H
@@ -44,7 +45,7 @@ Boston, MA 02110-1301, USA.  */
 #include "quadmath-imp.h"
 #include "gmp-impl.h"
 
-#ifdef HAVE_WCHAR_H
+#if defined(HAVE_WCHAR_H) && !defined(__DJGPP__)
 #define L_(x) L##x
 #else
 #define L_(x) x
diff --git a/libstdc++-v3/config/os/djgpp/error_constants.h b/libstdc++-v3/config/os/djgpp/error_constants.h
index 4ce342c9626..b89b07cb4be 100644
--- a/libstdc++-v3/config/os/djgpp/error_constants.h
+++ b/libstdc++-v3/config/os/djgpp/error_constants.h
@@ -33,6 +33,15 @@
 #include <bits/c++config.h>
 #include <cerrno>
 
+#ifndef EOPNOTSUPP
+// Use same value as in wat3222br6.zip file net/watt/sys/djgpp.err
+#define EOPNOTSUPP 52
+#endif
+
+#ifndef ENOTSUP
+#define ENOTSUP 101
+#endif
+
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -118,9 +127,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 //    not_connected = 				ENOTCONN,
       not_enough_memory = 			ENOMEM,
 
-#ifdef _GLIBCXX_HAVE_ENOTSUP
       not_supported = 				ENOTSUP,
-#endif
 
 #ifdef _GLIBCXX_HAVE_ECANCELED
       operation_canceled = 			ECANCELED,
@@ -128,7 +135,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 //    operation_in_progress = 			EINPROGRESS,
       operation_not_permitted = 		EPERM,
-//    operation_not_supported = 		EOPNOTSUPP,
+      operation_not_supported = 		EOPNOTSUPP,
 //    operation_would_block = 			EWOULDBLOCK,
 
 #ifdef _GLIBCXX_HAVE_EOWNERDEAD
diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h
index 512167f6f2d..de56387511e 100644
--- a/libstdc++-v3/include/experimental/bits/fs_path.h
+++ b/libstdc++-v3/include/experimental/bits/fs_path.h
@@ -53,6 +53,11 @@
 # include <algorithm>
 #endif
 
+#if defined(__DJGPP__)
+# define _GLIBCXX_FILESYSTEM_IS_DJGPP 1
+# include <algorithm>
+#endif
+
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 namespace experimental
@@ -460,6 +465,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     {
 #ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
       return __ch == L'/' || __ch == preferred_separator;
+#elif defined(_GLIBCXX_FILESYSTEM_IS_DJGPP)
+      return __ch == '/' || __ch == '\\';
 #else
       return __ch == '/';
 #endif
@@ -826,6 +833,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 #ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
     std::replace(_M_pathname.begin(), _M_pathname.end(), L'/',
 		 preferred_separator);
+#elif defined(_GLIBCXX_FILESYSTEM_IS_DJGPP)
+    std::replace(_M_pathname.begin(), _M_pathname.end(), '\\',
+		 preferred_separator);
 #endif
     return *this;
   }
@@ -997,7 +1007,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   inline bool
   path::is_absolute() const
   {
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+#if defined(_GLIBCXX_FILESYSTEM_IS_WINDOWS) \
+  || defined(_GLIBCXX_FILESYSTEM_IS_DJGPP)
     return has_root_name();
 #else
     return has_root_directory();
diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 8de3511346e..9da49f9b233 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -269,8 +269,10 @@ namespace
       return file_type::fifo;
     else if (S_ISLNK(st.st_mode))
       return file_type::symlink;
+#ifdef S_ISSOCK
     else if (S_ISSOCK(st.st_mode))
       return file_type::socket;
+#endif // s_ISSOCK
 #endif
     return file_type::unknown;
 
diff --git a/libstdc++-v3/src/filesystem/path.cc b/libstdc++-v3/src/filesystem/path.cc
index c66d52bf4b0..a4e5f348a24 100644
--- a/libstdc++-v3/src/filesystem/path.cc
+++ b/libstdc++-v3/src/filesystem/path.cc
@@ -370,8 +370,13 @@ path::_M_split_cmpts()
 	_M_add_root_dir(0);
       ++pos;
     }
-#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+#if defined(_GLIBCXX_FILESYSTEM_IS_WINDOWS) \
+  || defined(_GLIBCXX_FILESYSTEM_IS_DJGPP)
+#ifdef __DJGPP__
+  else if (len > 1 && _M_pathname[1] == ':')
+#else
   else if (len > 1 && _M_pathname[1] == L':')
+#endif
     {
       // got disk designator
       _M_add_root_name(2);