C construct help please

[Bruce Wood]

What is the proper PowerBasic DLL v6-7 function export type
if the C construct is a return of LPLong.

Thank You.

Bruce



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[Tom Hanlin]

The LP prefix means "pointer". A C long is a PowerBASIC LONG. So,
you're looking at a generic 32-bit return value-- use a DWORD or
a LONG-- and understand that the result is actually a pointer to
a LONG value. (Because FUNCTION..AS LONG PTR isn't valid syntax,
but you can always return a LONG PTR as a LONG or a DWORD, since
the data types are effectively the same under 32-bit Windows).


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Tom Hanlin
PowerBASIC Staff

[Bruce Wood]

Thx Tom:

I'm familar with the syntax.
As Export Long Ptr was not valid, and Long or Dword is not working, I thought maybe I was doing something wrong.

I guess I still am.

Thx again for the prompt post.

Bruce

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[Don Dickinson]

a pointer is a long (or dword), just do an export DWORD ...
e.g.

function getLongPointer alias "getLongPointer" (iLong as Long) export as Long
  function = varptr(iLong)
end function

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dickinson.basicguru.com

[Bruce Wood]

Well, It should have worked, but alas.

I need to get the contains of the supposedly LPLong.

The @ affixed to the returned LPLong/Dword/Long does not get the desired value.

Very Annoying.

Thx everyone for your help.

Bruce



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[Lance Edmonds]

It should be very easy... just assign the DWORD/LONG return value to a local pointer of the right data type:

DIM px AS LONG PTR, x AS LONG
px = RetLongPointer(param)
x = @px
...
FUNCTION RetLongPointer() AS DWORD
  STATIC result AS LONG ' the returned pointer target must be persistent
                        ' so returning a pointer to a LOCAL is BAD, BAD, BAD!  
  ... code here that generates the value stored in 'result'
  FUNCTION = VARPTR(result)
END FUNCTION

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Bern Ertl]

Is the LpLong a parameter to a function call or the return value
of the function?

If a parameter, simply use a LONG variable BYREF when calling.

If a return type, Lance's sample above should work.


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Bernard Ertl