[[ Bug 22130 ]] Disable deleted object pool creation whilst debugging

runrevmark · runrevmark · commit 41fe259d56c4 · 2019-10-03T08:46:14.000+01:00
This patch adds a 'freeze' count to the deleted object pool logic. When the current
pool is frozen, no new pools will be created until it is thawed again. This means
that all objects that are deleted during that period are accumulated in the frozen
pool.

This ability is used inside MCB_prepmessage, which is the handler which causes the
engine to enter debug mode and send a message. Doing this prevents corruption of
the deleted object pools stack which appears to occur when the script editor
manipulates menus in the context of a debug-related message.

As the use of freezing the current object pool is only used in this one place it
has no effect on normal running code, only on code which runs in the context of
a debug-related message.
diff --git a/docs/notes/bugfix-22130.md b/docs/notes/bugfix-22130.md
@@ -0,0 +1 @@
+# Improve stability of breakpoint manipulation in the S/E whilst debugging
diff --git a/engine/src/debug.cpp b/engine/src/debug.cpp
@@ -284,7 +284,9 @@ void MCB_prepmessage(MCExecContext &ctxt, MCNameRef mess, uint2 line, uint2 pos,
 		p3.setnext(&p4);
 		p4.setvalueref_argument(p_info);
 	}
-	MCB_message(ctxt, mess, &p1);
+    MCDeletedObjectsFreezePool();
+    MCB_message(ctxt, mess, &p1);
+    MCDeletedObjectsThawPool();
 	if (id != 0)
 		MCeerror->clear();
 	if (added)
diff --git a/engine/src/object.cpp b/engine/src/object.cpp
@@ -5519,6 +5519,7 @@ struct MCDeletedObjectPool
 static MCDeletedObjectPool *MCsparedeletedobjectpool = nil;
 static MCDeletedObjectPool *MCdeletedobjectpool = nil;
 static MCDeletedObjectPool *MCrootdeletedobjectpool = nil;
+static uint32_t MCdeletedobjectpoolfreezedepth = 0;
 
 static bool MCDeletedObjectPoolCreate(MCDeletedObjectPool*& r_pool)
 {
@@ -5604,8 +5605,22 @@ void MCDeletedObjectsTeardown(void)
     }
 }
 
+void MCDeletedObjectsFreezePool(void)
+{
+    MCdeletedobjectpoolfreezedepth += 1;
+}
+
+void MCDeletedObjectsThawPool(void)
+{    
+    MCdeletedobjectpoolfreezedepth -= 1;
+}
+
 void MCDeletedObjectsEnterWait(bool p_dispatching)
 {
+    // If the current pool is frozen, do nothing
+    if (MCdeletedobjectpoolfreezedepth > 0)
+        return;
+    
     // If this isn't a dispatching wait, then no objects can be created.
     if (!p_dispatching)
         return;
@@ -5632,6 +5647,10 @@ void MCDeletedObjectsEnterWait(bool p_dispatching)
 
 void MCDeletedObjectsLeaveWait(bool p_dispatching)
 {
+    // If the current pool is frozen, do nothing
+    if (MCdeletedobjectpoolfreezedepth > 0)
+        return;
+    
     // If this isn't a dispatching wait, then no objects can be created.
     if (!p_dispatching)
         return;
diff --git a/engine/src/object.h b/engine/src/object.h
@@ -506,6 +506,8 @@ struct MCExecValue;
 struct MCDeletedObjectPool;
 void MCDeletedObjectsSetup(void);
 void MCDeletedObjectsTeardown(void);
+void MCDeletedObjectsFreezePool(void);
+void MCDeletedObjectsThawPool(void);
 void MCDeletedObjectsEnterWait(bool p_dispatching);
 void MCDeletedObjectsLeaveWait(bool p_dispatching);
 void MCDeletedObjectsOnObjectCreated(MCObject *object);

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+# Improve stability of breakpoint manipulation in the S/E whilst debugging`