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);
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)Originally Posted by favetelinguis
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
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 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
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)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);
Last edited by adeyblue; 01-25-2012 at 06:59 PM.
