From 7a1f3177c92556c4ca224d28fc881686845c5052 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@duempel.org>
Date: Mon, 14 Jul 2014 16:24:07 +0200
Subject: util/Cast: reimplement as template without macro

---
 src/util/Cast.hxx | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

(limited to 'src/util/Cast.hxx')

diff --git a/src/util/Cast.hxx b/src/util/Cast.hxx
index 8eb3479b8..680f81704 100644
--- a/src/util/Cast.hxx
+++ b/src/util/Cast.hxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2013 Max Kellermann <max@duempel.org>
+ * Copyright (C) 2013-2014 Max Kellermann <max@duempel.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -64,11 +64,31 @@ OffsetCast(const U *p, ptrdiff_t offset)
 	return reinterpret_cast<const T *>(OffsetPointer(p, offset));
 }
 
+template<class C, class A>
+static constexpr inline ptrdiff_t
+ContainerAttributeOffset(const C *null_c, const A C::*p)
+{
+    return ptrdiff_t((const char *)null_c - (const char *)&(null_c->*p));
+}
+
+template<class C, class A>
+static constexpr inline ptrdiff_t
+ContainerAttributeOffset(const A C::*p)
+{
+    return ContainerAttributeOffset<C, A>(nullptr, p);
+}
+
 /**
  * Cast the given pointer to a struct member to its parent structure.
  */
-#define ContainerCast(p, container, attribute) \
-	OffsetCast<container, decltype(((container*)nullptr)->attribute)> \
-	((p), -ptrdiff_t(offsetof(container, attribute)))
+template<class C, class A>
+#if defined(__clang__) || GCC_CHECK_VERSION(4,7)
+constexpr
+#endif
+static inline C &
+ContainerCast(A &a, A C::*member)
+{
+    return *OffsetCast<C, A>(&a, ContainerAttributeOffset<C, A>(member));
+}
 
 #endif
-- 
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