FindFirstDevice issue -- very weird

I met some very very weird issue using FindFirstDevice. I'm using Visual
Studio 2005 and WM5 PPC SDK
Following code works fine (either in emulator or real device -- imate JAQ3):
int _tmain(int argc, _TCHAR* argv[])
{
WCHAR * searchName= L"";
::DEVMGR_DEVICE_INFORMATION pdi;
HANDLE
h=::FindFirstDevice(DeviceSearchType::DeviceSearchByDeviceName,searchName,&pdi);
return 0;
}
but , if we call "FindFirstDevice" in a function not main, it won't work
(neither emulator nor real device work):
like following code, it would return -1.
void foo()
{
WCHAR * searchName= L"";
::DEVMGR_DEVICE_INFORMATION pdi;
HANDLE
h=::FindFirstDevice(DeviceSearchType::DeviceSearchByDeviceName,searchName,&pdi);

}
int _tmain(int argc, _TCHAR* argv[])
{
foo();
return 0;
}

Or even we just call a memset to set pdi to 0 , it won't work
int _tmain(int argc, _TCHAR* argv[])
{
WCHAR * searchName= L"";
::DEVMGR_DEVICE_INFORMATION pdi;
memset(&pdi,0,sizeof(DEVMGR_DEVICE_INFORMATION));
HANDLE
h=::FindFirstDevice(DeviceSearchType::DeviceSearchByDeviceName,searchName,&pdi);
return 0;
}

I"m pretty sure there must be something wrong with the implementation of
this function -- sounds it rely on some random memory.

Paul
Thu Oct 04 14:19:43 PDT 2007

If you don't set pdi.dwSize=sizeof(DEVMGR_DEVICE_INFORMATION) before
calling FindFirstDevice it will return INVALID_HANDLE(-1) and
GetLastError will return 87(Invalid Parameter)

Paul Monson
Intrinsyc


Liang Zhu wrote:
> I met some very very weird issue using FindFirstDevice. I'm using Visual
> Studio 2005 and WM5 PPC SDK
> Following code works fine (either in emulator or real device -- imate JAQ3):
> int _tmain(int argc, _TCHAR* argv[])
> {
> WCHAR * searchName= L"";
> ::DEVMGR_DEVICE_INFORMATION pdi;
> HANDLE
> h=::FindFirstDevice(DeviceSearchType::DeviceSearchByDeviceName,searchName,&pdi);
> return 0;
> }
> but , if we call "FindFirstDevice" in a function not main, it won't work
> (neither emulator nor real device work):
> like following code, it would return -1.
> void foo()
> {
> WCHAR * searchName= L"";
> ::DEVMGR_DEVICE_INFORMATION pdi;
> HANDLE
> h=::FindFirstDevice(DeviceSearchType::DeviceSearchByDeviceName,searchName,&pdi);
>
> }
> int _tmain(int argc, _TCHAR* argv[])
> {
> foo();
> return 0;
> }
>
> Or even we just call a memset to set pdi to 0 , it won't work
> int _tmain(int argc, _TCHAR* argv[])
> {
> WCHAR * searchName= L"";
> ::DEVMGR_DEVICE_INFORMATION pdi;
> memset(&pdi,0,sizeof(DEVMGR_DEVICE_INFORMATION));
> HANDLE
> h=::FindFirstDevice(DeviceSearchType::DeviceSearchByDeviceName,searchName,&pdi);
> return 0;
> }
>
> I"m pretty sure there must be something wrong with the implementation of
> this function -- sounds it rely on some random memory.