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diff --git a/gl/m4/time_r.m4 b/gl/m4/time_r.m4
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+dnl Reentrant time functions like localtime_r.
+
+dnl Copyright (C) 2003, 2006, 2007, 2008 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.
+
+dnl Written by Paul Eggert.
+
+AC_DEFUN([gl_TIME_R],
+[
+ dnl Persuade glibc and Solaris <time.h> to declare localtime_r.
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
+  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  AC_REQUIRE([AC_C_RESTRICT])
+
+  AC_CACHE_CHECK([whether localtime_r is compatible with its POSIX signature],
+    [gl_cv_time_r_posix],
+    [AC_TRY_COMPILE(
+       [#include <time.h>],
+       [/* We don't need to append 'restrict's to the argument types,
+           even though the POSIX signature has the 'restrict's,
+           since C99 says they can't affect type compatibility.  */
+        struct tm * (*ptr) (time_t const *, struct tm *) = localtime_r;
+        if (ptr) return 0;
+        /* Check the return type is a pointer.  On HP-UX 10 it is 'int'.  */
+        *localtime_r (0, 0);],
+       [gl_cv_time_r_posix=yes],
+       [gl_cv_time_r_posix=no])])
+  if test $gl_cv_time_r_posix = yes; then
+    REPLACE_LOCALTIME_R=0
+  else
+    REPLACE_LOCALTIME_R=1
+    AC_LIBOBJ([time_r])
+    gl_PREREQ_TIME_R
+  fi
+])
+
+# Prerequisites of lib/time_r.c.
+AC_DEFUN([gl_PREREQ_TIME_R], [
+  :
+])