Access Violation while calculating a pointer - c++

Question

I'm quite afraid the question is really, really simple, but even thou I'm starting to grip the idea of pointers, hints from experienced users shorten the time I need to spend on it to understand everything. Ive got a simple example, I won't go into details what its supposed to do later on, because I think my mistake is something very basic. I'm getting:
Exception thrown: read access violation.
_First was 0x815110.
When executing this code:
#include <Windows.h>
#include <iostream>
#include "Header.h"
#pragma comment(linker, "/SECTION:.data,RWE")
using std::cout;
using std::endl;
int main() {
DWORD dwProcessID = 0;
cout << "Looking for game process..." << endl;
while (dwProcessID == 0) {
dwProcessID = GetProcessID(L"PathOfExile.exe");
Sleep(100);
}
std::cout << "Game Client found" << std::endl;
printf("dwProcessID = %p\n", dwProcessID);
HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPMODULE, dwProcessID);
MODULEENTRY32 module;
module.dwSize = sizeof(MODULEENTRY32);
Module32First(snapshot, &module);
HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, false, dwProcessID);
HANDLE hToken = NULL;
if (!OpenProcessToken(hProcess, TOKEN_ADJUST_PRIVILEGES, &hToken))
printf("Failed to open access token\n");
if (!SetPrivilege(hToken, SE_DEBUG_NAME, TRUE))
printf("Failed to set debug privilege\n");
printf("PoE base address = %p\n", module.modBaseAddr);
BYTE jmp[] = "\xBA\x00\x00\x80\x3F\x89\x10\x89\x16\xE9\x00\x00\x00\x00";
BYTE *dwMaphack = (BYTE*)(module.modBaseAddr + 0x4D5110);
cout << dwMaphack << endl;
*(DWORD*)&jmp[10] = (DWORD)(dwMaphack - jmp) - 6;
DWORD dwOldProt;
VirtualProtectEx(hProcess, (LPVOID)dwMaphack, 8, PAGE_EXECUTE_READWRITE, &dwOldProt);
// tbc
while (1) {
}
return 0;
}
The open process methods and other basic stuff are in the header and they do work fine, what I don't get is why when I change the byte pointer BYTE *dwMaphack to DWORD *dwMaphack, there's no longer an access violation error?
I'm trying to base my code on an outdated code of someones that no longer works, so the reason for doing these operations is only partially known for me, I know what it's supposed to do in programming terms, but I don't know the effect in the game, yet. I don't think it's important in terms of the error I'm getting anyway. Thanks in advance for the answers!

Answer 1

BYTE is an alias for unsigned char.
std::cout has an overloaded operator<< that accepts an unsigned char* pointer as input and prints it as a character string (as stated by Harry Johnston, https://stackoverflow.com/a/41538200/7376565). So it crashes when it tries to access memory it does not have access to.
std::cout does not have an operator<< overload for DWORD* (aka unsigned long*), but it does have one for void*, so any non-character pointer will print just the value of the pointer itself. When you change dwMaphack to DWORD*, operator<< doesn't try to access the memory that dwMaphack points to, so no access violation occurs.

Answer 2

Here's your problem:
cout << dwMaphack << endl;
This is attempting to print the value that dwMaphack points to, not the value of the pointer. Since the pointer is only valid in the remote process, attempting to dereference it results in an access violation.
This works:
cout << (DWORD_PTR)dwMaphack << endl;