Add configure check for restrict keyword.

config.h.in

@@ -1509,6 +1509,21 @@
 /* Define to an OS-specific initialization function or 'os_init_common'. */
 #undef os_init
 
+/* Define to the equivalent of the C99 'restrict' keyword, or to
+   nothing if this is not supported.  Do not define if restrict is
+   supported only directly.  */
+#undef restrict
+/* Work around a bug in older versions of Sun C++, which did not
+   #define __restrict__ or support _Restrict or __restrict__
+   even though the corresponding Sun C compiler ended up with
+   "#define restrict _Restrict" or "#define restrict __restrict__"
+   in the previous line.  This workaround can be removed once
+   we assume Oracle Developer Studio 12.5 (2016) or later.  */
+#if defined __SUNPRO_CC && !defined __RESTRICT && !defined __restrict__
+# define _Restrict
+# define __restrict__
+#endif
+
 /* Define as 'int' if <sys/types.h> doesn't define. */
 #undef uid_t
 

configure

@@ -19022,6 +19022,57 @@ printf "%s\n" "#define const /**/" >>confdefs.h
 
 fi
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
+printf %s "checking for C/C++ restrict keyword... " >&6; }
+if test ${ac_cv_c_restrict+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e) ac_cv_c_restrict=no
+   # Put '__restrict__' first, to avoid problems with glibc and non-GCC; see:
+   # https://lists.gnu.org/archive/html/bug-autoconf/2016-02/msg00006.html
+   # Put 'restrict' last, because C++ lacks it.
+   for ac_kw in __restrict__ __restrict _Restrict restrict; do
+     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+typedef int *int_ptr;
+	   int foo (int_ptr $ac_kw ip) { return ip[0]; }
+	   int bar (int [$ac_kw]); /* Catch GCC bug 14050.  */
+	   int bar (int ip[$ac_kw]) { return ip[0]; }
+
+int
+main (void)
+{
+int s[1];
+	   int *$ac_kw t = s;
+	   t[0] = 0;
+	   return foo (t) + bar (t);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  ac_cv_c_restrict=$ac_kw
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+     test "$ac_cv_c_restrict" != no && break
+   done
+   ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_restrict" >&5
+printf "%s\n" "$ac_cv_c_restrict" >&6; }
+
+ case $ac_cv_c_restrict in
+   restrict) ;;
+   no) printf "%s\n" "#define restrict /**/" >>confdefs.h
+ ;;
+   *)  printf "%s\n" "#define restrict $ac_cv_c_restrict" >>confdefs.h
+ ;;
+ esac
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for inline" >&5
 printf %s "checking for inline... " >&6; }
 if test ${ac_cv_c_inline+y}

configure.ac

@@ -2364,6 +2364,7 @@ dnl AC_PROG_CC_STDC is deprecated in autoconf 2.70 and above.
 dnl
 m4_bmatch(m4_defn([AC_AUTOCONF_VERSION]), [^2\.69], [AC_PROG_CC_STDC])
 AC_C_CONST
+AC_C_RESTRICT
 AC_C_INLINE
 AC_C_VOLATILE
 SUDO_CPP_VARIADIC_MACROS