Calling subroutines from dll

I am trying to call routines from a vendor supplied dll. They helpfully gave me a header file, but little else. The header of the subroutine that I'm trying to call reads:
_LYDYAQCW_API DWORD GetSysVersion(WORD* version, WORD* release, WORD* patch, DWORD DriverHandle);
I interpreted the DWORD as U32, and WORD as U16 with * as "point to value". Running the VI causes LabVIEW to disappear instantly with not-so-much as a whisper. Can anyone help, with this problem and more generally, how to interpret the datatypes in Windows APIs. The one document I have found does not have these types.
Thanks,
Damian
Attachments:
LaseLecTmp.vi ‏14 KB

Wise Owl wrote:
> Rolf, thanks for your help in this matter. Immediately, by changing
> the calling convention to C, LabVIEW does not crash. There is a
> InitDriver function that it looks like I should call. However, the
> handle is defined by "LPDWORD DriverHandle". Does this not imply that
> the value is passed, making it impossible for the function to pass
> back a handle? Do you have any idea how I can find a lookup table to
> translate LPDWORD, WORD, etc. into LabVIEW specific byte counts?
Well, if you are familiar with C you can look at the Windows SDK headers
to find out what they mean. Most of these basic types are defined in
WinDef.h.
A short explanation
LP stands for Long Pointer meaning a 32 bit pointer (pass as pointer)
P sta
nds for Pointer (meaning the same as LP in modern Windows at least
until we get 64 bit Windows.)
BYTE is an unsigned 8 bit integer
WORD is an unsigned 16 bit integer
DWORD or UINT is an unsigned 32 bit integer
CHAR is a signed 8 bit integer
SHORT a signed 16 bit integer
LONG or INT a signed 32 bit interger
BOOL a boolean (a 32 bit integer in fact)
HANDLE (and almost any type starting with H..) a handle (just treat it
as 32 bit unsigned int)
So in your case the parameter LPDWORD would mean to configure an
unsigned 32 bit integer which should be passed by reference (as pointer).
> Making a call to this function produces an exception which stops the
> Call Library Function Node. Probably because I have the wrong
> variable types defined.
If you configure the parameter to be passed as value (not a pointer)
this would be what should happen.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

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