From 9d63c8220bc01693691618cd507f8d57434bfac0 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Mon, 20 Aug 2018 14:23:02 +0200
Subject: [PATCH] util/Cast: reverse operands in ContainerAttributeOffset()

The result shall be positive.
---
 src/util/Cast.hxx | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/util/Cast.hxx b/src/util/Cast.hxx
index d71fb593e..21075f1ce 100644
--- a/src/util/Cast.hxx
+++ b/src/util/Cast.hxx
@@ -53,7 +53,7 @@ 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));
+	return ptrdiff_t((const char *)&(null_c->*p) - (const char *)null_c);
 }
 
 template<class C, class A>
@@ -70,7 +70,7 @@ template<class C, class A>
 static inline constexpr C &
 ContainerCast(A &a, const A C::*member)
 {
-	return *OffsetCast<C, A>(&a, ContainerAttributeOffset<C, A>(member));
+	return *OffsetCast<C, A>(&a, -ContainerAttributeOffset<C, A>(member));
 }
 
 /**
@@ -80,7 +80,7 @@ template<class C, class A>
 static inline constexpr const C &
 ContainerCast(const A &a, const A C::*member)
 {
-	return *OffsetCast<const C, const A>(&a, ContainerAttributeOffset<C, A>(member));
+	return *OffsetCast<const C, const A>(&a, -ContainerAttributeOffset<C, A>(member));
 }
 
 #endif