Merge branch 'release/debian/3.23-1'debian/3.23-1

1 files changed, 30 insertions, 18 deletions

diff --git a/include/libHX/defs.h b/include/libHX/defs.h
index bb03f40..9ecdd32 100644
--- a/include/libHX/defs.h
+++ b/include/libHX/defs.h
@@ -22,6 +22,9 @@
 #		define containerof(var, type, member) reinterpret_cast<type *>( \
 			reinterpret_cast<char *>(var) - offsetof(type, member))
 #	endif
+#	ifndef static_cast
+#		define static_cast(T, x) static_cast<T>(x)
+#	endif
 
 template<typename new_type>
 static __inline__ new_type signed_cast(const char *expr)
@@ -91,24 +94,33 @@ static __inline__ new_type signed_cast(unsigned char *expr)
 			((struct { type x; }){(expr)}.x)
 #	endif
 #	if defined(__GNUC__) && !defined(__clang__) && !defined(const_cast1)
-#		define __const_cast_strip1(expr) \
-			__typeof__(*(union { int z; __typeof__(expr) x; }){0}.x)
-#		define __const_cast_strip2(expr) \
-			__typeof__(**(union { int z; __typeof__(expr) x; }){0}.x)
-#		define __const_cast_strip3(expr) \
-			__typeof__(***(union { int z; __typeof__(expr) x; }){0}.x)
-#		define const_cast1(new_type, expr) ({ \
-			BUILD_BUG_ON(!__builtin_types_compatible_p(__const_cast_strip1(expr), __const_cast_strip1(new_type))); \
-			(new_type)(expr); \
-		})
-#		define const_cast2(new_type, expr) ({ \
-			BUILD_BUG_ON(!__builtin_types_compatible_p(__const_cast_strip2(expr), __const_cast_strip2(new_type))); \
-			(new_type)(expr); \
-		})
-#		define const_cast3(new_type, expr) ({ \
-			BUILD_BUG_ON(!__builtin_types_compatible_p(__const_cast_strip3(expr), __const_cast_strip3(new_type))); \
-			(new_type)(expr); \
-		})
+		/*
+		 * The idea starts with (in abstract notation)
+		 * 	typeof deref typeof expr
+		 * To deref something, we need an object, which we can get by
+		 * creating a temporary aggregate, such as a union, of which
+		 * the member is accessed and dereferenced.
+		 * 	*(union { __typeof__(expr) x; }){init}.x
+		 * union has two nice properties:
+		 * - with an additional dummy member, we do not have to
+		 *   initialize x according to its type, which, if expr is
+		 *   an array type, may want extra braces.
+		 * - and with that dummy member, we also avoid the ugly
+		 *   "literal 0 is implicitly convertible to a pointer".
+		 * Unfortunately, this all requires C99 compound initializers.
+		 * That's ok - gcc and clang only treat it as a warning even
+		 * under strict C89 - and if you still force strict C89 on
+		 * yourself, you have a lot to answer for either way.
+		 */
+#		define __const_cast_strip(ptrs, expr) \
+			__typeof__(ptrs(union { int z; __typeof__(expr) x; }){0}.x)
+#		define __const_cast_p(ptrs, new_type, expr) ((new_type)( \
+			(expr) + \
+			BUILD_BUG_ON_EXPR(!__builtin_types_compatible_p(__const_cast_strip(ptrs, expr), __const_cast_strip(ptrs, new_type))) \
+		))
+#		define const_cast1(new_type, expr) __const_cast_p(*, new_type, expr)
+#		define const_cast2(new_type, expr) __const_cast_p(**, new_type, expr)
+#		define const_cast3(new_type, expr) __const_cast_p(***, new_type, expr)
 #	endif
 #	ifndef signed_cast
 #		define signed_cast(type, expr)      ((type)(expr))