From 4f638c0e31240b2fed9aa5035c25dc08e309ae15 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicholas.marriott@gmail.com>
Date: Fri, 25 Sep 2020 10:04:52 +0100
Subject: Check if UNIX 03 is needed for CMSG_DATA, for newer Solaris. From
 Eric N Vander Weele.

---
 configure.ac | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index f89c590b..82be9254 100644
--- a/configure.ac
+++ b/configure.ac
@@ -328,8 +328,9 @@ AC_SEARCH_LIBS(inet_ntoa, nsl)
 AC_SEARCH_LIBS(socket, socket)
 AC_CHECK_LIB(xnet, socket)
 
-# Check for CMSG_DATA. Some platforms require _XOPEN_SOURCE_EXTENDED (for
-# example see xopen_networking(7) on HP-UX).
+# Check for CMSG_DATA. On some platforms like HP-UX this requires UNIX 95
+# (_XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED) (see xopen_networking(7)). On
+# others, UNIX 03 (_XOPEN_SOURCE 600, see standards(7) on Solaris).
 XOPEN_DEFINES=
 AC_MSG_CHECKING(for CMSG_DATA)
 AC_EGREP_CPP(
@@ -362,6 +363,25 @@ if test "x$found_cmsg_data" = xno; then
 	AC_MSG_RESULT($found_cmsg_data)
 	if test "x$found_cmsg_data" = xyes; then
 		XOPEN_DEFINES="-D_XOPEN_SOURCE -D_XOPEN_SOURCE_EXTENDED"
+	fi
+fi
+if test "x$found_cmsg_data" = xno; then
+	AC_MSG_CHECKING(if CMSG_DATA needs _XOPEN_SOURCE 600)
+	AC_EGREP_CPP(
+		yes,
+		[
+			#define _XOPEN_SOURCE 600
+			#include <sys/socket.h>
+			#ifdef CMSG_DATA
+			yes
+			#endif
+		],
+		found_cmsg_data=yes,
+		found_cmsg_data=no
+	)
+	AC_MSG_RESULT($found_cmsg_data)
+	if test "x$found_cmsg_data" = xyes; then
+		XOPEN_DEFINES="-D_XOPEN_SOURCE=600"
 	else
 		AC_MSG_ERROR("CMSG_DATA not found")
 	fi
-- 
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