Access violation using FtpFindFirstFile unicode version in async mode - c++

Question

Let's say I have very simple little code sample which uses async WinInet:
#include "stdafx.h"
#include "WinInet.h"
#pragma comment(lib, "wininet.lib")
DWORD LatestResult = 0;
HANDLE MayContinue = 0;
VOID CALLBACK
CallBack(
__in HINTERNET hInternet,
__in DWORD_PTR dwContext,
__in DWORD dwInternetStatus,
__in_bcount(dwStatusInformationLength) LPVOID lpvStatusInformation,
__in DWORD dwStatusInformationLength
)
{
if (dwInternetStatus == INTERNET_STATUS_REQUEST_COMPLETE)
{
LatestResult = ((LPINTERNET_ASYNC_RESULT)lpvStatusInformation)->dwResult;
SetEvent (MayContinue);
}
}
int APIENTRY _tWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPTSTR lpCmdLine,
_In_ int nCmdShow)
{
MayContinue = ::CreateEvent (NULL, FALSE, FALSE, NULL);
HINTERNET Session = InternetOpen (NULL, INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, INTERNET_FLAG_ASYNC);
INTERNET_STATUS_CALLBACK CallbackPointer = InternetSetStatusCallback (Session, (INTERNET_STATUS_CALLBACK) CallBack);
MayContinue = ::CreateEvent (NULL, FALSE, FALSE, NULL);
InternetConnect (Session, _T ("ftp.secureftp-test.com"), INTERNET_INVALID_PORT_NUMBER, _T ("test"), _T ("test"), INTERNET_SERVICE_FTP, 0, 1);
WaitForSingleObject (MayContinue, INFINITE);
HINTERNET Internet = (HINTERNET) LatestResult;
WIN32_FIND_DATA *FindData = new WIN32_FIND_DATA;
FtpFindFirstFileW (Internet, _T ("*.*"), FindData, 0, 1);
WaitForSingleObject (MayContinue, INFINITE);
delete FindData;
return 0;
}
What I've got after execution:
Unhandled exception at 0xBAADF00D in WinInetTest.exe:
0xC0000005: Access violation executing location 0xBAADF00D.
It happens somewhere around final WaitForSingleObject and callstack is rather confusing.
But if I change
WIN32_FIND_DATA *FindData = new WIN32_FIND_DATA;
FtpFindFirstFileW (Internet, _T ("*.*"), FindData, 0, 1);
to
WIN32_FIND_DATAA *FindData = new WIN32_FIND_DATAA;
FtpFindFirstFileA (Internet, "*.*", FindData, 0, 1);
It executes and works as it should.
So my question is - am I really not doing something correctly or it just failure on WinInet side?
I'm testing it on Windows 7 using Visual Studio 2012 btw.

Answer 1

I also had difficulty with FtpFindFirstFileW. When I converted my project from MBCS to Unicode FtpFindFirstFileW resulted in an access violation that appeared to be a pointer dereference of 0xbaadf00d somewhere after the call, possibly when the async result was being prepared. I worked around this by using FtpFindFirstFileA, InternetFindNextFileA and the WIN32_FIND_DATAA struct in both MBCS and Unicode builds. I then convert the output cFileName field to a TCHAR string.

Answer 2

I'd recommend changing compiler setting Character Set from Unicode to Multi-Byte Character Set. The same thing was happening to me.