From 1d266aa8347fadfb0db34ae27df7b728c0ab2171 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Sat, 19 Apr 2014 02:38:32 -0700
Subject: [PATCH] Add a GCC-specific STATIC_UPCAST macro that checks the object
 type

The check is compile time, and is functionally identical to the old/alternate
version.
---
 Alc/backends/base.h                | 2 +-
 Alc/midi/base.h                    | 2 +-
 OpenAL32/Include/alAuxEffectSlot.h | 2 +-
 OpenAL32/Include/alMain.h          | 9 ++++++++-
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/Alc/backends/base.h b/Alc/backends/base.h
index 905c3ea4..d18ca400 100644
--- a/Alc/backends/base.h
+++ b/Alc/backends/base.h
@@ -61,7 +61,7 @@ DECLARE_THUNK(T, ALCbackend, ALint64, getLatency)                             \
 DECLARE_THUNK(T, ALCbackend, void, lock)                                      \
 DECLARE_THUNK(T, ALCbackend, void, unlock)                                    \
 static void T##_ALCbackend_Delete(void *ptr)                                  \
-{ T##_Delete(STATIC_UPCAST(T, ALCbackend, ptr)); }                            \
+{ T##_Delete(STATIC_UPCAST(T, ALCbackend, (ALCbackend*)ptr)); }               \
                                                                               \
 DECLARE_ALCBACKEND_VTABLE(T) = {                                              \
     T##_ALCbackend_Destruct,                                                  \
diff --git a/Alc/midi/base.h b/Alc/midi/base.h
index 75332006..42a4c279 100644
--- a/Alc/midi/base.h
+++ b/Alc/midi/base.h
@@ -99,7 +99,7 @@ DECLARE_THUNK(T, MidiSynth, void, reset)                                      \
 DECLARE_THUNK1(T, MidiSynth, void, update, ALCdevice*)                        \
 DECLARE_THUNK2(T, MidiSynth, void, process, ALuint, ALfloatBUFFERSIZE*restrict) \
 static void T##_MidiSynth_Delete(void *ptr)                                   \
-{ T##_Delete(STATIC_UPCAST(T, MidiSynth, ptr)); }                             \
+{ T##_Delete(STATIC_UPCAST(T, MidiSynth, (MidiSynth*)ptr)); }                 \
                                                                               \
 static const struct MidiSynthVtable T##_MidiSynth_vtable = {                  \
     T##_MidiSynth_Destruct,                                                   \
diff --git a/OpenAL32/Include/alAuxEffectSlot.h b/OpenAL32/Include/alAuxEffectSlot.h
index 75eb87ca..bc871111 100644
--- a/OpenAL32/Include/alAuxEffectSlot.h
+++ b/OpenAL32/Include/alAuxEffectSlot.h
@@ -33,7 +33,7 @@ DECLARE_THUNK1(T, ALeffectState, ALboolean, deviceUpdate, ALCdevice*)         \
 DECLARE_THUNK2(T, ALeffectState, void, update, ALCdevice*, const ALeffectslot*) \
 DECLARE_THUNK3(T, ALeffectState, void, process, ALuint, const ALfloat*restrict, ALfloatBUFFERSIZE*restrict) \
 static void T##_ALeffectState_Delete(void *ptr)                               \
-{ return T##_Delete(STATIC_UPCAST(T, ALeffectState, ptr)); }                  \
+{ return T##_Delete(STATIC_UPCAST(T, ALeffectState, (ALeffectState*)ptr)); }  \
                                                                               \
 static const struct ALeffectStateVtable T##_ALeffectState_vtable = {          \
     T##_ALeffectState_Destruct,                                               \
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index ad305c4e..8b66e4e7 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -348,8 +348,15 @@ static const union {
 
 #define DERIVE_FROM_TYPE(t)          t t##_parent
 #define STATIC_CAST(to, obj)         (&(obj)->to##_parent)
+#ifdef __GNUC__
+#define STATIC_UPCAST(to, from, obj) __extension__({                          \
+    static_assert(__builtin_types_compatible_p(from, __typeof(*(obj))),       \
+                  "Invalid upcast object from type");                         \
+    (to*)((char*)(obj) - offsetof(to, from##_parent));                        \
+})
+#else
 #define STATIC_UPCAST(to, from, obj) ((to*)((char*)(obj) - offsetof(to, from##_parent)))
-
+#endif
 
 #define DECLARE_FORWARD(T1, T2, rettype, func)                                \
 rettype T1##_##func(T1 *obj)                                                  \