Question

I recently moved from inline assembly to high level language (C++) where I want to set the result from a value^0x1A3C into a short type pointer (WORD PTR) but I am getting the following error:

A value of type int cannot be used to initialize an entity of type short*

I got the problem when passing an int type to a short*:

void PacketEncrypt(Packet* packet, int sizeofpacket)
{
    char* pointer;
    pointer = ((char*)packet+sizeofpacket) -2;
    short *pointer = packet->PacketSize^0x1A3C;
    packet->Type += 0x0FFF7;
}

What I want the compiler to make:

0041585E   8B45 0C          MOV EAX,DWORD PTR SS:[EBP+C]
00415861   8B4D 08          MOV ECX,DWORD PTR SS:[EBP+8]
00415864   8D5401 FE        LEA EDX,DWORD PTR DS:[ECX+EAX-2]
00415868   8955 F8          MOV DWORD PTR SS:[EBP-8],EDX
0041586B   8B45 08          MOV EAX,DWORD PTR SS:[EBP+8]
0041586E   0FBF08           MOVSX ECX,WORD PTR DS:[EAX]
00415871   81F1 3C1A0000    XOR ECX,1A3C
00415877   8B55 F8          MOV EDX,DWORD PTR SS:[EBP-8]
0041587A   880A             MOV WORD PTR DS:[EDX],CX

Answer 1

Assuming you want to write the calculated value to the location that pointer points to:

*reinterpret_cast<short*>(pointer) = packet->PacketSize^0x1A3C;

reinterpret_cast means “take an object of one type and force it into another type”, and is the cast used to convert between pointers to unrelated types; the value is assigned as if pointer pointed to short. Note that this might cause undefined behaviour if the pointer doesn’t have the correct alignment for short. In general, reinterpret_cast removes compile-time type checks, leaving the onus on the programmer to make sure the result is used correctly.