假设我有一个非常简单的代码示例使用异步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;
}
执行后的结果:
Unhandled exception at 0xBAADF00D in WinInetTest.exe:
0xC0000005: Access violation executing location 0xBAADF00D.
它发生在final WaitForSingleObject的某个地方,callstack相当令人困惑。
但是如果我改变WIN32_FIND_DATA *FindData = new WIN32_FIND_DATA;
FtpFindFirstFileW (Internet, _T ("*.*"), FindData, 0, 1);
WIN32_FIND_DATAA *FindData = new WIN32_FIND_DATAA;
FtpFindFirstFileA (Internet, "*.*", FindData, 0, 1);
它执行并正常工作。所以我的问题是-我真的没有做正确的事情或它只是失败在WinInet方面?
我正在Windows 7上使用Visual Studio 2012进行测试。
我使用FtpFindFirstFileW也有困难。当我将我的项目从MBCS转换为Unicode时,FtpFindFirstFileW导致访问冲突,似乎是调用后某个地方的0xbaadf00d的指针解引用,可能是在准备异步结果时。我通过在MBCS和Unicode构建中使用FtpFindFirstFileA, InternetFindNextFileA和WIN32_FIND_DATAA结构体来解决这个问题。然后将输出的cFileName字段转换为TCHAR字符串。
我建议将编译器设置字符集从Unicode改为多字节字符集。同样的事情也发生在我身上。