From 2b72f35c324e3a0623894f9c678bd08341973a32 Mon Sep 17 00:00:00 2001
From: frsyuki <frsyuki@users.sourceforge.jp>
Date: Wed, 20 Jan 2010 14:49:51 +0900
Subject: [PATCH] configure.in: show error message if __sync_* atomic
 operations are not supported

---
 configure.in | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/configure.in b/configure.in
index 99c43521..6bf1b486 100644
--- a/configure.in
+++ b/configure.in
@@ -24,7 +24,7 @@ if test "$enable_cxx" != "no"; then
 	fi
 fi
 
-# FIXME
+# FIXME enable_cxx
 AC_PROG_CXX
 
 CXXFLAGS="-O4 -Wall $CXXFLAGS -I.. -I../c"
@@ -34,6 +34,22 @@ AC_CHECK_HEADERS(tr1/unordered_map)
 AC_CHECK_HEADERS(tr1/unordered_set)
 AC_LANG_POP([C++])
 
+AC_CACHE_CHECK([for __sync_* atomic operations], msgpack_cv_atomic_ops, [
+    AC_TRY_LINK([
+        int atomic_sub(int i) { return __sync_sub_and_fetch(&i, 1); }
+        int atomic_add(int i) { return __sync_add_and_fetch(&i, 1); }
+    ], [], msgpack_cv_atomic_ops="yes")
+    ])
+if test "$msgpack_cv_atomic_ops" != "yes"; then
+    AC_MSG_ERROR([__sync_* atomic operations are not supported.
+Note that gcc < 4.1 is not supported.
+If you are using gcc-4.1 and the CPU architecture is x86, try to add
+CFLAGS"--march=i686" and CXXFLAGS="-march=i668" options to ./configure as follows:
+
+  $ ./configure CFLAGS="-march=i686" CXXFLAGS="-march=i686"
+])
+fi
+
 AM_CONDITIONAL(ENABLE_CXX, test "$enable_cxx" != "no")
 
 AC_PROG_LIBTOOL