Keep track of references to effect slots, so they aren't deleted while in use

OpenAL32/Include/alAuxEffectSlot.h

@@ -21,6 +21,8 @@ typedef struct ALeffectslot
     ALfloat Gain;
     ALboolean AuxSendAuto;
 
+    ALuint refcount;
+
     // Index to itself
     ALuint effectslot;
 

OpenAL32/alAuxEffectSlot.c

@@ -70,6 +70,7 @@ AL_API ALvoid AL_APIENTRY alGenAuxiliaryEffectSlots(ALsizei n, ALuint *effectslo
 
                     (*list)->Gain = 1.0;
                     (*list)->AuxSendAuto = AL_TRUE;
+                    (*list)->refcount = 0;
 
                     effectslots[i] = (ALuint)ALTHUNK_ADDENTRY(*list);
                     (*list)->effectslot = effectslots[i];
@@ -112,6 +113,15 @@ AL_API ALvoid AL_APIENTRY alDeleteAuxiliaryEffectSlots(ALsizei n, ALuint *effect
                 alSetError(AL_INVALID_NAME);
                 break;
             }
+            else
+            {
+                ALAuxiliaryEffectSlot = (ALeffectslot*)ALTHUNK_LOOKUPENTRY(effectslots[i]);
+                if(ALAuxiliaryEffectSlot->refcount > 0)
+                {
+                    alSetError(AL_INVALID_NAME);
+                    break;
+                }
+            }
         }
 
         if (i == n)

OpenAL32/alSource.c

@@ -745,7 +745,13 @@ ALAPI void ALAPIENTRY alSource3i(ALuint source, ALenum eParam, ALint lValue1, AL
                     ALeffectslot *ALEffectSlot = (ALeffectslot*)ALTHUNK_LOOKUPENTRY(lValue1);
                     ALfilter     *ALFilter = (ALfilter*)ALTHUNK_LOOKUPENTRY(lValue3);
 
+                    /* Release refcount on the previous slot, and add one for
+                     * the new slot */
+                    if(pSource->Send[lValue2].Slot)
+                        pSource->Send[lValue2].Slot->refcount--;
                     pSource->Send[lValue2].Slot = ALEffectSlot;
+                    if(pSource->Send[lValue2].Slot)
+                        pSource->Send[lValue2].Slot->refcount++;
 
                     if(!ALFilter)
                     {