Problem Reading Process Memory

I am having a strange problem. For a fun little test, I decided to see if I could get some minesweeper info out of memory. For some reason though, ReadProcessMemory() fails every time. I am not sure why because with this same code I was previously reading some memory from other processes. I have tried opening the process with PROCESS_ALL_ACCESS but to no avail. Can anyone point me in the right direction?

Also, point out any bad code practices.

Code:

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#include <stdio.h>
#include <windows.h>

typedef unsigned long  DWORD;

int main(void)
{
        HWND hWnd = FindWindow(NULL, "Minesweeper");
        HWND pHandle;
        DWORD PID;

        unsigned long lpWidth = 0x1005334;
        unsigned long bytesread;
        unsigned int width;
       
        if (hWnd == NULL)
        {
                printf("Window not found\n");
                return 1;
        }

        printf("Window Handle = %x\n", hWnd);

        GetWindowThreadProcessId(hWnd, &PID);

        printf("Process ID = %x\n", PID);

        pHandle = OpenProcess(PROCESS_ALL_ACCESS, 1, PID);

        printf("Process Handle = %x\n", pHandle);

        if (pHandle == NULL)
        {
                printf("The Process handle could not be retrieved\n");
                return 1;
        }

        if (ReadProcessMemory(pHandle, &lpWidth, &width, sizeof(width), &bytesread))
        {
                printf("Width = %d\n", width);
        }
        else
        {
                printf("ReadProcessMemory Failed\n");
        }


        return 0;
}

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What does GetLastError() return after ReadProcessMemory or OpenProcess?
Are you on XP or Vista?

XP, and 299

So, the error means:
Only part of a ReadProcessMemory or WriteProcessMemory request was completed.

However, I think the problem is that you are passing the parameter lpBaseAddress incorrectly.

You probably want to do:

Code:

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        const void *lpWidth = (void *)0x1005334;

        ReadProcessMemory(pHandle, lpWidth, &width, sizeof(width), &bytesread)

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Mats

Thank you so much, that was correct.

It's strange because from the source I was studying from stored it as an int.

You were taking the address of a local variable (operator &!) instead of passing the value in the variable.

This

Code:

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HWND pHandle;

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should be this

Code:

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HANDLE pHandle;

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Quote:

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Originally Posted by BobS0327

This

Code:

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HWND pHandle;

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should be this

Code:

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HANDLE pHandle;

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Your right, it still worked though lol.

Quote:

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Originally Posted by carrotcake1029

Your right, it still worked though lol.

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All "handles" on Windows are really just integers. C will unfortunately allow silent conversion between handle types. The specific type used ("HWND" or "HANDLE" or whatever) is really just to remind you, the programmer, what it is. If you make a mistake, Windows won't know.

Quote:

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Originally Posted by brewbuck

All "handles" on Windows are really just integers. C will unfortunately allow silent conversion between handle types. The specific type used ("HWND" or "HANDLE" or whatever) is really just to remind you, the programmer, what it is. If you make a mistake, Windows won't know.

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But of course, if you have a HWND and pass it in as a PROCESS handle, then you hopefully get an error, and certainly the the expected result - just because they are the same type.

[And I thought a HANDLE was a void *, but perhaps I'm wrong].

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Mats

HANDLE = void*
HWND = struct with one int (don't ask me why they implemented it as such).

Quote:

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Originally Posted by Elysia

HANDLE = void*
HWND = struct with one int (don't ask me why they implemented it as such).

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Because a struct with one int has a name - which in turn means that you CAN differentiate between different types of types, which leads to the question of why the compiler doesn't complain about type mismatch.

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Mats

Quote:

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Originally Posted by matsp

Because a struct with one int has a name - which in turn means that you CAN differentiate between different types of types, which leads to the question of why the compiler doesn't complain about type mismatch.

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Mats

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Actually, the MS compilers do complain:

Quote:

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error C2440: '=' : cannot convert from 'void *' to 'struct HWND__ *'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast

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