Re: dynamic loading of dll's, ccall

From: [at]} <skulski{>
Date: Thu, 12 Feb 2004 02:10:42 -0500 (EST)

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Doug wrote:

> Looking back over the work I did at X-ray Instrumentation Associates I
> see that I called a non-CP generated dll. In this case the CP
> 'interface' file needed to specify the functions in the dll had to be
> tagged with the ccall flag.

For the current laser project I am calling a DLL supplied by National
Instruments. I used StdCall. This DLL was most likely created
with C, because all their examples use C. I also found by trial and
error that the DLL procedures need be called using a "normal" name
(e.g., imgSnap) rather than "decorated" name like _imgSnap{([at]})nowhere.xy
I am not sure how the DLL was created to avoid "decorated" names.

> When a dll is generated by CP and used by CP then the ccall flag is not
> needed (your code works from CP whether or not you specify ccall but I
> speculate that the parameters are left on the stack when you do. Try a
> long loop repeatly calling the procedure (without I/O) to see if you get
> a stack overflow).

I did not specify the [ccall] flag and the program is working.
I tested the result only a few times. I am hoping that this does not
mean that after a hundred calls the stack will overflow and the
machine will crash?

> When the dll is generated by CP but is expected to be used by non-CP
> languages that use the ccall convention then within the generating
> module one must use the ccall flag.

I am using StdCall, though the DLL was most likely created with C.

Wojtek


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Received on Thu Feb 12 2004 - 08:10:42 UTC