pack the TMegaPkt struct. define TMEGAPKT_SIZE.

memcpy((char *)&packeta[1] - packeta->dwSpaceLeft, packet, dwSize);

Source/msg.cpp does this calculation, which will be wrong if any padding is
added. To get this to work correctly, pack the structures, as suggested by
@AJenbo.

Also, define TMEGAPKT_SIZE because pNext can be 4 or 8 bytes.

Source/msg.cpp

@@ -55,7 +55,7 @@ TMegaPkt *msg_get_next_packet()
 {
 	TMegaPkt *result;
 
-	sgpCurrPkt = (TMegaPkt *)DiabloAllocPtr(32008);
+	sgpCurrPkt = (TMegaPkt *)DiabloAllocPtr(TMEGAPKT_SIZE);
 	sgpCurrPkt->pNext = NULL;
 	sgpCurrPkt->dwSpaceLeft = 32000;
 

structs.h

@@ -955,11 +955,14 @@ typedef struct DJunk {
 } DJunk;
 #pragma pack(pop)
 
+#pragma pack(push, 1)
 typedef struct TMegaPkt {
 	struct TMegaPkt *pNext;
 	DWORD dwSpaceLeft;
 	BYTE data[32000];
 } TMegaPkt;
+#pragma pack(pop)
+#define TMEGAPKT_SIZE sizeof(TMegaPkt)
 
 typedef struct TBuffer {
 	DWORD dwNextWriteOffset;