From d767d10322ba312a71cbf5f655588d600ce5c0fb Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <c.oelckers@zdoom.fake>
Date: Sat, 21 May 2016 13:11:43 +0200
Subject: [PATCH] - made PSprites submission GC aware.

---
 src/d_player.h |  2 +-
 src/p_pspr.cpp | 55 +++++++++++++++++++++++++++++++++++++++-----------
 src/p_pspr.h   |  6 +++---
 3 files changed, 47 insertions(+), 16 deletions(-)

diff --git a/src/d_player.h b/src/d_player.h
index e743a7b4f7..650799f6d9 100644
--- a/src/d_player.h
+++ b/src/d_player.h
@@ -436,6 +436,7 @@ public:
 
 	AWeapon	   *ReadyWeapon;
 	AWeapon	   *PendingWeapon;			// WP_NOCHANGE if not changing
+	TObjPtr<DPSprite> psprites; // view sprites (gun, etc)
 
 	int			cheats;					// bit flags
 	int			timefreezer;			// Player has an active time freezer
@@ -528,7 +529,6 @@ public:
 	int GetSpawnClass();
 
 	// PSprite layers
-	DPSprite *psprites; // view sprites (gun, etc)
 	void TickPSprites();
 	void DestroyPSprites();
 	DPSprite *GetPSprite(psprnum_t layer); // Used ONLY for compatibility with the old hardcoded layers.
diff --git a/src/p_pspr.cpp b/src/p_pspr.cpp
index 11433b6f81..f2ab02b82a 100644
--- a/src/p_pspr.cpp
+++ b/src/p_pspr.cpp
@@ -113,12 +113,25 @@ END_POINTERS
 DPSprite::DPSprite(player_t *owner, AInventory *caller, int id)
 : processPending(true), firstTic(true), Owner(owner), Caller(caller), ID(id)
 {
-	DPSprite **prev = &Owner->psprites;
-	while (*prev && (*prev)->ID < ID)
-		prev = &(*prev)->Next;
-
-	Next = *prev;
-	*prev = this;
+	DPSprite *prev = nullptr;
+	DPSprite *next = Owner->psprites;
+	while (next != nullptr && next->ID < ID)
+	{
+		prev = next;
+		next = next->Next;
+	}
+	Next = next;
+	GC::WriteBarrier(this, next);
+	if (prev == NULL)
+	{
+		Owner->psprites = this;
+		GC::WriteBarrier(this);
+	}
+	else
+	{
+		prev->Next = this;
+		GC::WriteBarrier(prev, this);
+	}
 
 	if (Next && Next->ID == ID && ID != 0)
 		Next->Destroy(); // Replace it.
@@ -1349,10 +1362,13 @@ void DPSprite::Serialize(FArchive &arc)
 void player_t::DestroyPSprites()
 {
 	DPSprite *pspr = psprites;
+	psprites = nullptr;
 	while (pspr)
 	{
+		DPSprite *next = pspr->Next;
+		pspr->Next = nullptr;
 		pspr->Destroy();
-		pspr = pspr->Next;
+		pspr = next;
 	}
 }
 
@@ -1364,12 +1380,27 @@ void player_t::DestroyPSprites()
 
 void DPSprite::Destroy()
 {
-	DPSprite **prev = &Owner->psprites;
-	while (*prev != this)
-		prev = &(*prev)->Next;
-
-	*prev = Next;
+	// Do not crash if this gets called on partially initialized objects.
+	if (Owner != nullptr && Owner->psprites != nullptr)
+	{
+		if (Owner->psprites != this)
+		{
+			DPSprite *prev = Owner->psprites;
+			while (prev != nullptr && prev->Next != this)
+				prev = prev->Next;
 
+			if (prev != nullptr && prev->Next == this)
+			{
+				prev->Next = Next;
+				GC::WriteBarrier(prev, Next);
+			}
+		}
+		else
+		{
+			Owner->psprites = Next;
+			GC::WriteBarrier(Next);
+		}
+	}
 	Super::Destroy();
 }
 
diff --git a/src/p_pspr.h b/src/p_pspr.h
index 87e78ef1f8..5f9292d98e 100644
--- a/src/p_pspr.h
+++ b/src/p_pspr.h
@@ -66,8 +66,8 @@ public:
 	int					GetSprite()	const { return Sprite; }
 	int					GetFrame()	const { return Frame; }
 	FState*				GetState()	const { return State; }
-	DPSprite*			GetNext()	const { return Next; }
-	TObjPtr<AInventory>	GetCaller()	const { return Caller; }
+	DPSprite*			GetNext()	      { return Next; }
+	AInventory*			GetCaller()	      { return Caller; }
 
 	double x, y;
 	double oldx, oldy;
@@ -82,7 +82,7 @@ private:
 	void Destroy();
 
 	TObjPtr<AInventory> Caller;
-	DPSprite *Next;
+	TObjPtr<DPSprite> Next;
 	player_t *Owner;
 	FState *State;
 	int Sprite;