WriteProcessMemory returns 0 in C++ - c++

Question

I am developing a small cash hack for GTA V and I found that when I use
WriteProcessMemory(hp, (LPVOID)0x1417C4C18, &cashVal, (DWORD)sizeof(cashVal), 0)
that the WriteProcessMemory returns 0. Here is the full source code of my small hack.
#include <Windows.h>
#include <iostream>
#include <cstdlib>
using namespace std;
int main()
{
int cashVal = 0;
cout << "Enter the amount of cash you want: " << endl;
cin >> cashVal;
HWND hwnd = FindWindow(0, "Grand Theft Auto V");
if (hwnd == 0) {
cout << "Cannot find the GTAV window. Make sure its running in Windowed mode!" << endl;
}
else {
DWORD pid;
GetWindowThreadProcessId(hwnd, &pid);
HANDLE hp = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
if (!hp) {
cout << "Could not get a handle to GTAV. Try again :(" << endl;
}
else {
int success = WriteProcessMemory(hp, (LPVOID)0x1417C4C18, &cashVal, (DWORD)sizeof
(cashVal), 0);
if (success > 0) {
cout << "You now have " << cashVal << " money!" << endl;
}
else {
cout << "Writing the memory failed!" << endl;
cout << "Error code: " << success << endl;
}
CloseHandle(hp);
}
}
cin.get();
return 0;
}
I basically ask the user to input the cash they want, and it's meant to set it in the game, but it returns a code of 0 and fails. It doesn't fail trying to find the game window because it doesn't print that message to the standard output. Please help me!
NOTE: The hack will be used on single player

Answer 1

First, don't use PROCESS_ALL_ACCESS. Only request what you actually need. WriteProcessMemory() only needs PROCESS_VM_WRITE and PROCESS_VM_OPERATION access, so request only that.
Like many other API functions, when WriteProcessMemory() fails, GetLastError() will tell you why. Your code is assuming that WriteProcessMemory() itself returns an error code directly, but it does not. It returns a BOOL (not an int) to indicate success or failure, and then GetLastError() returns the error code if failure. This is documented behavior:
Return value
If the function succeeds, the return value is nonzero.
If the function fails, the return value is 0 (zero). To get extended error information, call GetLastError. The function fails if the requested write operation crosses into an area of the process that is inaccessible.
Try this:
#include <windows.h>
#include <iostream>
#include <cstdlib>
using namespace std;
int main()
{
int cashVal = 0;
cout << "Enter the amount of cash you want: " << endl;
cin >> cashVal;
HWND hwnd = FindWindow(0, "Grand Theft Auto V");
if (hwnd == 0) {
cout << "Cannot find the GTAV window. Make sure its running in Windowed mode!" << endl;
}
else {
DWORD pid;
GetWindowThreadProcessId(hwnd, &pid);
HANDLE hp = OpenProcess(PROCESS_VM_WRITE | PROCESS_VM_OPERATION, FALSE, pid);
if (!hp) {
cout << "Could not get a handle to GTAV. Try again :(" << endl;
}
else {
BOOL success = WriteProcessMemory(hp, (LPVOID)0x1417C4C18, &cashVal, sizeof(cashVal), 0);
if (success) {
cout << "You now have " << cashVal << " money!" << endl;
}
else {
DWORD errCode = GetLastError();
cout << "Writing the memory failed!" << endl;
cout << "Error code: " << errCode << endl;
}
CloseHandle(hp);
}
}
cin.get();
return 0;
}

Answer 2

You are most likely trying to write to a memory path where you don't have access to... probably you are using a 32-bit program to write to a 64-bit memory address(that's if u use a 64-bit computer), I think I had this problem a few years back porting solved my problem then forgive me if I am wrong atleast that was what I thought.
Try the code on a 32-bit address and if it works... that solves your problem.
And for the Getting_Last_Error you can add this lil' bit of functionality I use.
void PrintLastErrorMsg(){
LPTSTR pTmp = NULL;
DWORD errnum = GetLastError();
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_ARGUMENT_ARRAY,
NULL,
errnum,
LANG_NEUTRAL,
(LPTSTR)&pTmp,
0,
NULL
);
cout << "Error(" << errnum << "): " << pTmp << endl;
}
Be free to make changes.