From ba0bcf078a88b02c9ebe853cacb126fb45c2fe60 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sat, 23 Jul 2011 22:19:15 +0200
Subject: Provide different implementations for ODB_POTENTIALLY_UNUSED

The same approach does not work for VC++ and GCC.
---
 odb/details/unused.hxx | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/odb/details/unused.hxx b/odb/details/unused.hxx
index bf1638f..31ceb52 100644
--- a/odb/details/unused.hxx
+++ b/odb/details/unused.hxx
@@ -8,7 +8,15 @@
 
 #include <odb/pre.hxx>
 
-#define ODB_POTENTIALLY_UNUSED(x) (void*)&x
+// VC++ doesn't like the (void)x expression if x is a reference to
+// an incomplete type. On the other hand, GCC warns that (void*)&x
+// doesn't have any effect.
+//
+#ifdef _MSC_VER
+#  define ODB_POTENTIALLY_UNUSED(x) (void*)&x
+#else
+#  define ODB_POTENTIALLY_UNUSED(x) (void)x
+#endif
 
 #include <odb/post.hxx>
 
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