From cc5ba66a89d9c14ade7528b63ede7944523042d8 Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Thu, 15 Oct 2009 23:56:41 +0200
Subject: [PATCH] configure.ac: Added the --enable-standards command line
 option.

This option may be used to enable C99 and POSIX.1 2001 standards compliance
mode.
---
 configure.ac | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/configure.ac b/configure.ac
index abd0c5e..e0fd5db 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,6 +30,37 @@ test_cc_flags() {
 	return $ret
 }
 
+dnl Optionally stick to standard C99 and POSIX.1 2001 as close as possible.
+AC_ARG_ENABLE([standards],
+		AS_HELP_STRING([--enable-standards],
+				[Enable standards compliance mode]),
+		[enable_standards="$enableval"],
+		[enable_standards="no"])
+
+if test "x$enable_standards" = "xyes"; then
+	AC_DEFINE([_ISOC99_SOURCE], 1,
+			[Define to enforce ISO/IEC 9899:1999 (C99) compliance.])
+	AC_DEFINE([_POSIX_C_SOURCE], 200112L,
+			[Define to enforce IEEE 1003.1-2001 (POSIX:2001) compliance.])
+	AC_DEFINE([_XOPEN_SOURCE], 600,
+			[Define to enforce X/Open 6 (XSI) compliance.])
+	AC_DEFINE([_REENTRANT], 1,
+			[Define to enable reentrant interfaces.])
+	AC_DEFINE([_THREAD_SAFE], 1,
+			[Define to enable reentrant interfaces.])
+
+	for flag in -std=c99 -pedantic; do
+		AC_MSG_CHECKING([whether $CC accepts $flag])
+
+		if test_cc_flags $flag; then
+			CFLAGS="$CFLAGS $flag"
+			AC_MSG_RESULT([yes])
+		else
+			AC_MSG_RESULT([no])
+		fi
+	done
+fi
+
 for flag in -Wall -Wextra -Werror; do
 	AC_MSG_CHECKING([whether $CC accepts $flag])
 
-- 
2.30.2