Type conversions and buffers make me sick

Im trying to take different values of type DWORD, HWND and add them to a listbox. However everytime i try to run the program it runs but locks down the computer and it does not work. What am i doing wrong?

Code:

char *buf;
//Returns a DWORD
processID = startup();

buf = (char*)GlobalAlloc(GPTR, 50);
itoa(processID, buf, 10);
index = SendDlgItemMessage(hwnd, IDC_LIST, LB_ADDSTRING, 0, (LPARAM)buf);

Originally Posted by favetelinguis

What am i doing wrong?

Not posting the part of your code with the error, as in, what you've posted would work fine (assuming the success of all those functions)

I got it to work now, it was not wrong with the code as you said. Just a strange error at another place in the code.

How would i do a dynamic allocation, as it is now buf is always 50 but i would like it to be only as big as it needs to house the DWORD. Also do i have to free any memory after this or can i use Alloc over and over without clearing anything?

To make it more clear is this how you use GlobalAlloc and only work with one variabel?

Code:

int index;
char *buf;
int strLen;


buf = (char*)GlobalAlloc(GPTR, 50);

itoa((int)myHWND, buf, 10);
index = SendDlgItemMessage(hwnd, IDC_LIST, LB_ADDSTRING, 0, (LPARAM)buf);

itoa((int)myHWND, buf, 10);
index = SendDlgItemMessage(hwnd, IDC_LIST, LB_ADDSTRING, 0, (LPARAM)buf);

strLen = GetWindowTextLength(myHWND);
buf = (char*)GlobalAlloc(GPTR, strLen+1);
GetWindowText(myHWND, buf, strLen);
index = SendDlgItemMessage(hwnd, IDC_LIST, LB_ADDSTRING, 0, (LPARAM)buf);

There's no need to use any allocation for the DWORD or the HWND, they have a set number of digits so just use stack buffers.
If you're using C++ you can make a big enough buffer for all the digits by including <limits> and using

Code:

const DWORD numDwordDigits = std::numeric_limits<DWORD>::digits10 + 1;
char dwordBuffer[numDwordDigits + 1];
// In C, you'll have to include <limits.h> and use this
char dwordBuffer[((CHAR_BIT * sizeof (DWORD)) * 301L / 1000) + 2];
_ultoa(processID, dwordBuffer, 10); // using _ultoa as that won't interpret big DWORDs as negative numbers

itoa doesn't work correctly with HWNDs, because they're 64-bit values if you compile your program as 64-bit. It's easiest to use _ui64toa instead. HWNDs are also usually displayed in base-16 rather than base-10.

Code:

const DWORD numHwndDigits = std::numeric_limits<HWND>::digits10 + 1;
char hwndBuffer[numHwndDigits + 1];
// In C, you'll have to include <limits.h> and use this
char hwndBuffer[((CHAR_BIT * sizeof (HWND)) * 301L / 1000) + 2];
_ui64toa((unsigned long long)myHWND, hwndBuffer, 16);

The text string one is alright, but just use malloc / new [] instead. Using GlobalAlloc doesn't gain you anything but extra typing. And yes you have to GlobalFree (for GlobalAlloc)/free (for malloc)/delete[] (for new[]) when you're finished with it (i.e. after calling SendDlgItemMessage)