Thread: Mysterious crashes in common file dialog

I get some mysterious crashes w/out any messages when working with Common File Dialogs. I have a Dialog Box with three edit controls and three buttons (IDC_BUTTON1, IDC_BUTTON2, IDC_BUTTON3) to browse for files. I want to fill the Edit controls with the file names. Usually when I am pushing the third button the application crashes without a warning. Below I give the code for one button in the Dialog procedure. The other two are identical except that ofn has to be replaced by ofn1 and ofn2, respectively. And szFileName is replaced by szFileName1 and szFileName2, respectively.

Code:

case IDC_BUTTON1:
				{

					ZeroMemory(&ofn, sizeof(ofn));
					
					ofn.lStructSize = sizeof(ofn);
					ofn.hwndOwner = hwnd;
					ofn.lpstrFilter = TEXT("Text Files (*.txt)\0*.txt\0All Files (*.*)\0*.*\0");
					ofn.lpstrFile = szFileName;
					ofn.nMaxFile = MAX_PATH;
					ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY;
					ofn.lpstrDefExt = TEXT("txt");

					if(GetOpenFileName(&ofn))
					{

						ILength = lstrlen(szFileName);
						buffer = (LPWSTR)GlobalAlloc(GPTR, ILength*sizeof(TCHAR));
						if(buffer)
						{
							wsprintf(buffer, szFileName);
							SetDlgItemText(hwnd, IDC_EDIT1, (LPWSTR) buffer);
							GlobalFree((HANDLE)buffer);
						}
					}

				}
			break;

And for completeness, the variables are as such:

Code:

	OPENFILENAME ofn, ofn1, ofn2;
	wchar_t szFileName[MAX_PATH] = TEXT("");
	wchar_t szFileName1[MAX_PATH] = TEXT("");
	wchar_t szFileName2[MAX_PATH] = TEXT("");
	int ILength;
	LPWSTR buffer;

Has anyone encountered this problem before? Thanx.

Ok, never mind. I found the problem. I made the classic mistake of allocating a buffer with the same length as the outcome of lstrlen. This way there is no space for the null terminating characters (in case of wide characters) and the application crashes.

oh, I thought TEXT() was terminating the string with an extra '\0'. Are you sure about the extra '\0', because the problem seems to be solved by replacing ILength by ILength + 1 in the allocation of buffer.

Originally Posted by novacain

AFAIK the TEXT() macro only 'converts' between UNICODE and ANSI depending on the define in the app, it does not add any terminators.

The fact that it's a string literal tells you it automatically ends in a null terminator, which in this case happens to be the second behind the explicit one.