diff --git a/m4/gnupg-ttyname.m4 b/m4/gnupg-ttyname.m4
new file mode 100644
index 00000000..f0ff554d
--- /dev/null
+++ b/m4/gnupg-ttyname.m4
@@ -0,0 +1,101 @@
+# ttyname_r.m4 serial 8
+dnl Copyright (C) 2010-2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_TTYNAME_R],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+
+  dnl Persuade Solaris <unistd.h> to provide the POSIX compliant declaration of
+  dnl ttyname_r().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_DECLS_ONCE([ttyname_r])
+  if test $ac_cv_have_decl_ttyname_r = no; then
+    HAVE_DECL_TTYNAME_R=0
+  fi
+
+  AC_CHECK_FUNCS([ttyname_r])
+  if test $ac_cv_func_ttyname_r = no; then
+    HAVE_TTYNAME_R=0
+  else
+    HAVE_TTYNAME_R=1
+    dnl On MacOS X 10.4 (and Solaris 10 without gl_USE_SYSTEM_EXTENSIONS)
+    dnl the return type is 'char *', not 'int'.
+    AC_CACHE_CHECK([whether ttyname_r is compatible with its POSIX signature],
+      [gl_cv_func_ttyname_r_posix],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[#include <stddef.h>
+              #include <unistd.h>]],
+            [[*ttyname_r (0, NULL, 0);]])
+         ],
+         [gl_cv_func_ttyname_r_posix=no],
+         [gl_cv_func_ttyname_r_posix=yes])
+      ])
+    if test $gl_cv_func_ttyname_r_posix = no; then
+      REPLACE_TTYNAME_R=1
+    else
+      AC_DEFINE([HAVE_POSIXDECL_TTYNAME_R], [1],
+        [Define if the ttyname_r function has a POSIX compliant declaration.])
+      dnl On Solaris 10, both ttyname_r functions (the one with the non-POSIX
+      dnl declaration and the one with the POSIX declaration) refuse to do
+      dnl anything when the output buffer is less than 128 bytes large.
+      dnl On OSF/1 5.1, ttyname_r ignores the buffer size and assumes the
+      dnl buffer is large enough.
+      AC_REQUIRE([AC_CANONICAL_HOST])
+      AC_CACHE_CHECK([whether ttyname_r works with small buffers],
+        [gl_cv_func_ttyname_r_works],
+        [
+          dnl Initial guess, used when cross-compiling or when /dev/tty cannot
+          dnl be opened.
+changequote(,)dnl
+          case "$host_os" in
+                      # Guess no on Solaris.
+            solaris*) gl_cv_func_ttyname_r_works="guessing no" ;;
+                      # Guess no on OSF/1.
+            osf*)     gl_cv_func_ttyname_r_works="guessing no" ;;
+                      # Guess yes otherwise.
+            *)        gl_cv_func_ttyname_r_works="guessing yes" ;;
+          esac
+changequote([,])dnl
+          AC_RUN_IFELSE(
+            [AC_LANG_SOURCE([[
+#include <fcntl.h>
+#include <unistd.h>
+int
+main (void)
+{
+  int result = 0;
+  int fd;
+  char buf[31]; /* use any size < 128 here */
+
+  fd = open ("/dev/tty", O_RDONLY);
+  if (fd < 0)
+    result |= 16;
+  else if (ttyname_r (fd, buf, sizeof (buf)) != 0)
+    result |= 17;
+  else if (ttyname_r (fd, buf, 1) == 0)
+    result |= 18;
+  return result;
+}]])],
+            [gl_cv_func_ttyname_r_works=yes],
+            [case $? in
+               17 | 18) gl_cv_func_ttyname_r_works=no ;;
+             esac],
+            [:])
+        ])
+      case "$gl_cv_func_ttyname_r_works" in
+        *yes) ;;
+        *) REPLACE_TTYNAME_R=1 ;;
+      esac
+    fi
+  fi
+])
+
+# Prerequisites of lib/ttyname_r.c.
+AC_DEFUN([gl_PREREQ_TTYNAME_R], [
+  AC_CHECK_FUNCS([ttyname])
+])