From 6c9abe0b728ace6ee238b4dbb7ad7322c55014c0 Mon Sep 17 00:00:00 2001
From: yoe <yoe>
Date: Wed, 16 Feb 2005 08:38:00 +0000
Subject: [PATCH] r103: Check for the right symbols in nbd.h by compiling,
 rather than guessing on whether they'll be there on the
 basis of other, unrelated, symbols. Also, make the error
 message that appears if we don't find what we need a bit
 more helpful, and warn the user if a bad nbd.h is found
 locally but a good one is provided system-wide.

---
 configure.ac |   35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/configure.ac b/configure.ac
index 5965ad3..80f6181 100644
--- a/configure.ac
+++ b/configure.ac
@@ -74,22 +74,31 @@ dnl We need to check for NBD_CMD_DISC, but that's part of an enum, it is not
 dnl #define'd. Therefore, we check for something which is differently #define'd
 dnl in the old or new versions, even if we don't really care about that.
 dnl This might break at some time, but it should work for now, so...
-AC_TRY_CPP([#include "nbd.h"
-#ifdef LOCAL_END_REQUEST
-#error not here
-#endif
-], 
-  [AC_DEFINE(NBD_H_LOCAL, 1, Set to 1 if a (recent enough) nbd.h can be found in the current directory)
-    NBD_H='"nbd.h"'],
-  AC_TRY_CPP([#include <linux/nbd.h>
-#ifdef LOCAL_END_REQUEST
-#error not here
-#endif
+AC_TRY_COMPILE([#include <stdio.h>
+#define MY_NAME "conftest"
+#define NBD_H_LOCAL
+#include "cliserv.h"
 ],
-    [AC_DEFINE(NBD_H_LINUX, 1, Set to 1 if a (recent enough) nbd.h can be found in the linux directory in the search path) NBD_H='<linux/nbd.h>'],
-    AC_MSG_ERROR(Could not find a (recent enough) nbd.h)
+[int foo=NBD_CMD_DISC], 
+  [AC_DEFINE(NBD_H_LOCAL, 1, Set to 1 if a (2.6) nbd.h can be found in the current directory)
+    NBD_H='"nbd.h"'],
+  AC_TRY_COMPILE([#include <stdio.h>
+#define MY_NAME "conftest"
+#define NBD_H_LINUX
+#include "cliserv.h"
+  ],
+[int foo=NBD_CMD_DISC],
+    [AC_DEFINE(NBD_H_LINUX, 1, Set to 1 if a (2.6) nbd.h can be found in the linux directory in the search path) NBD_H='<linux/nbd.h>'],
+    AC_MSG_ERROR(Could not find an nbd.h from 2.6 or above.)
   )
 )
+if test -f nbd.h
+then
+  if test $NBD_H='<linux/nbd.h>'
+  then
+    AC_MSG_WARN([there is a local nbd.h, but it is from the 2.4-series of kernels. Using the system-provided, working, nbd.h])
+  fi
+fi
 AC_MSG_RESULT($NBD_H)
 AC_CHECK_HEADERS([sys/mount.h],,,
 [[#include <sys/param.h>
-- 
1.7.10.4