invalid conversion from void* to int*
hi,
This is part of an online tutorial I'm going through, which is written in C but I'm trying to learn C++. I've been able to deal with most C>C++ issues in the tutorial until now.
From what I understand, (is?) this suppose to be typecasted ? I just don't know how to do that with pointers (yet) (still learning). Just looking for a (specific) solution to this particular problem, so I can move forward with learning the stuff I am doing.
Any help (& other pointers) appreciated, thanks.
I'm using Dev C++.
Error message
Code:
\main.cpp invalid conversion from `void*' to `int*'
Points to this line;
Code:
int *buf = GlobalAlloc(GPTR, sizeof(int) * count);
Entire code;
Code:
#include <windows.h>
#include "resource.h"
BOOL CALLBACK DlgProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
switch(Message)
{
case WM_INITDIALOG:
// This is where we set up the dialog box, and initialise any default values
SetDlgItemText(hwnd, IDC_TEXT, "This is a string");
SetDlgItemInt(hwnd, IDC_NUMBER, 5, FALSE);
break;
case WM_COMMAND:
switch(LOWORD(wParam))
{
case IDC_ADD:
{
// When somebody clicks the Add button, first we get the number of
// they entered
BOOL bSuccess;
int nTimes = GetDlgItemInt(hwnd, IDC_NUMBER, &bSuccess, FALSE);
if(bSuccess)
{
// Then we get the string they entered
// First we need to find out how long it is so that we can
// allocate some memory
int len = GetWindowTextLength(GetDlgItem(hwnd, IDC_TEXT));
if(len > 0)
{
// Now we allocate, and get the string into our buffer
int i;
char* buf;
buf = (char*)GlobalAlloc(GPTR, len + 1);
GetDlgItemText(hwnd, IDC_TEXT, buf, len + 1);
// Now we add the string to the list box however many times
// the user asked us to.
for(i = 0;i < nTimes; i++)
{
int index = SendDlgItemMessage(hwnd, IDC_LIST, LB_ADDSTRING, 0, (LPARAM)buf);
// Here we are associating the value nTimes with the item
// just for the heck of it, we'll use it to display later.
// Normally you would put some more useful data here, such
// as a pointer.
SendDlgItemMessage(hwnd, IDC_LIST, LB_SETITEMDATA, (WPARAM)index, (LPARAM)nTimes);
}
// Dont' forget to free the memory!
GlobalFree((HANDLE)buf);
}
else
{
MessageBox(hwnd, "You didn't enter anything!", "Warning", MB_OK);
}
}
else
{
MessageBox(hwnd, "Couldn't translate that number :(", "Warning", MB_OK);
}
}
break;
case IDC_REMOVE:
{
// When the user clicks the Remove button, we first get the number
// of selected items
HWND hList = GetDlgItem(hwnd, IDC_LIST);
int count = SendMessage(hList, LB_GETSELCOUNT, 0, 0);
if(count != LB_ERR)
{
if(count != 0)
{
// And then allocate room to store the list of selected items.
int i;
int *buf = GlobalAlloc(GPTR, sizeof(int) * count);
SendMessage(hList, LB_GETSELITEMS, (WPARAM)count, (LPARAM)buf);
// Now we loop through the list and remove each item that was
// selected.
// WARNING!!!
// We loop backwards, because if we removed items
// from top to bottom, it would change the indexes of the other
// items!!!
for(i = count - 1; i >= 0; i--)
{
SendMessage(hList, LB_DELETESTRING, (WPARAM)buf[i], 0);
}
GlobalFree(buf);
}
else
{
MessageBox(hwnd, "No items selected.", "Warning", MB_OK);
}
}
else
{
MessageBox(hwnd, "Error counting items :(", "Warning", MB_OK);
}
}
break;
case IDC_CLEAR:
SendDlgItemMessage(hwnd, IDC_LIST, LB_RESETCONTENT, 0, 0);
break;
case IDC_LIST:
switch(HIWORD(wParam))
{
case LBN_SELCHANGE:
{
// Get the number of items selected.
HWND hList = GetDlgItem(hwnd, IDC_LIST);
int count = SendMessage(hList, LB_GETSELCOUNT, 0, 0);
if(count != LB_ERR)
{
// We only want to continue if one and only one item is
// selected.
if(count == 1)
{
// Since we know ahead of time we're only getting one
// index, there's no need to allocate an array.
int index;
int err = SendMessage(hList, LB_GETSELITEMS, (WPARAM)1, (LPARAM)&index);
if(err != LB_ERR)
{
// Get the data we associated with the item above
// (the number of times it was added)
int data = SendMessage(hList, LB_GETITEMDATA, (WPARAM)index, 0);
SetDlgItemInt(hwnd, IDC_SHOWCOUNT, data, FALSE);
}
else
{
MessageBox(hwnd, "Error getting selected item :(", "Warning", MB_OK);
}
}
else
{
// No items selected, or more than one
// Either way, we aren't going to process this.
SetDlgItemText(hwnd, IDC_SHOWCOUNT, "-");
}
}
else
{
MessageBox(hwnd, "Error counting items :(", "Warning", MB_OK);
}
}
break;
}
break;
}
break;
case WM_CLOSE:
EndDialog(hwnd, 0);
break;
default:
return FALSE;
}
return TRUE;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
return DialogBox(hInstance, MAKEINTRESOURCE(IDD_MAIN), NULL, DlgProc);
}
