Coder's Guild Mailing List

Re: Calling DLL functions

Posted by DaRKFoRCe on 2000-03-08

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Hi,

Monday, March 06, 2000, 4:11:34 AM, you wrote:

tgoa> Date: Sun, 5 Mar 2000 15:24:57 EST
tgoa> From: Kspansel@xxx.xxx
tgoa> Subject: Calling DLL functions

tgoa> Hey all,
tgoa>     How would I go about calling a function from a DLL in C?  I want to use
tgoa> the windows cards.dll functions, but I don't know how to call them.  And how
tgoa> would I find out what they're prototypes look like?  Any links and
tgoa> information on using the cards.dll functions in C/C++ would be great.  Thanks.

tgoa> Kory Spansel

Dunno if this helps, but you can call the exported functions just like
calling any other functions, provided you link the import library for the
.dll with your .exe. The library basically takes care about loading
the apropriate dll and providing your .exe with its export table. This
is load-time linking.

Another way is run-time linking. You should not link your .exe with
the import library. Instead, you load the dll at run time using
LoadLibrary() or LoadLibraryEx() API, then you get the address of the
function you want to invoke by GetProcAddress() API. Invoke the
function by means of pointer to function then free the .dll if you
don't need it anymore.

The hard part is determining the function prototypes. I can't help you
with that, but one suggestion, try 'quick-view'-ing the .dll file in
explorer. The export table can be read there. Usually, the functions
in a .dll uses pascal calling convention. To verify this, usually the
function names in the export table are appended with '@some-number'.
This shows that the function is using pascal conventions. The
'some-number' part shows how many bytes the function are expecting as
argument. At least you know how many bytes to pass to the function.

If you are desperate, you can always debug the exported functions by
means of a window debugger (softice comes in mind). But it sure ain't
pretty trying to figure out those asm opcodes cause source-level
debugging is definitely out of question.

DaRKFoRCe
darkforce@xxxxxxxxxxx.xxx

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