Parameter types in FORTRAN DLL's

Question

Hi
I am a novice to fortran programing but want to use existing fortran code
within Labview. I have Digital Visual Fortran 5.0A and have suceeded in making
an elementary .DLL and calling it with the Labview call library function.
However, this only works if I set the parameter types to 'Adapt to Type'.
If I try to specify the types Labview crashes with an invalid page fault.
This particular example has only real parameters. I have tried with arrays
and have even less sucess as the 'Adapt to Type' option does not even work
in these cases.
Any help or explanation would be most appreciated.
Rory Stieger
PS : If it's any help here is the fortran code (the commented out bits for
the test with arrays)
ccccccccccccccccc
cccccccccccccccccccccccccc
c subroutine ftoc (n,f,c)
subroutine ftoc (f,c)
implicit none
!DEC$ ATTRIBUTES DLLEXPORT :: ftoc
!DEC$ ATTRIBUTES ALIAS :'ftoc'::ftoc
c integer n,i
c real*8 f,c(n)
real*8 f,c
c do i=1,n
c c(i) = (5.0/9.0) * (f*i-32.0)
c = (5.0/9.0) * (f-32.0)
c end do
return
end
ccccccccccccccccccccccccccccccccccccccccccc

Answer 1

[posted and mailed]
[email protected] (Rory Stieger) wrote in <[email protected]>:
>
>Hi
>
>I am a novice to fortran programing but want to use existing fortran
>code within Labview. I have Digital Visual Fortran 5.0A and have
>suceeded in making an elementary .DLL and calling it with the Labview
>call library function.
>
>
>However, this only works if I set the parameter types to 'Adapt to
>Type'. If I try to specify the types Labview crashes with an invalid
>page fault. This particular example has only real parameters. I have
>tried with arrays and have even less sucess as the 'Adapt to Type'
>option does not even work in these cases.
>
>Any help or explanation would be most appreciated.
>
>Rory Stieger
>
>PS : If it's any help here is the fortran code (the commented out bits
>for the test with arrays)
>
>ccccccccccccccccccccccccccccccccccccccccccc
>c subroutine ftoc (n,f,c)
> subroutine ftoc (f,c)
> implicit none
> !DEC$ ATTRIBUTES DLLEXPORT :: ftoc
> !DEC$ ATTRIBUTES ALIAS :'ftoc'::ftoc
>c integer n,i
>c real*8 f,c(n)
> real*8 f,c
>c do i=1,n
>c c(i) = (5.0/9.0) * (f*i-32.0)
> c = (5.0/9.0) * (f-32.0)
>c end do
> return
> end
>ccccccccccccccccccccccccccccccccccccccccccc
>
First of all when passing arrays you need to define them before passing
them to the call library node. So use the init tool before hand to allocate
memory for the array before passing it (This causes a lot of crashes if not
done correctly).
Secondly, the type of call the dll uses is important. Usually you can set
the dll fucntions to have the standard call and you then configure the call
library node to take this into account.
Thirdly, you need to find out how fortran passes parameters. I cannot
remember enough of my fortran to help. But, for example if all values are
passed by reference then configure all your call library parameters as
(*varname). Otherewise by value they would be (varname). In the example
above if they are not passed by reference then you will not receive any
valid value in "c" on return from the subroutine.
Fourthly, some function calls in some languages return values by default
even though the standard way of accessing them might not use the return
value. Check out whether fortran is returning a void function, otherwise
you might need to set up a return in the call library node.
Lastly, make sure that the types match in the parameters. For example is
your int 32 or 16 bit by default?
cheers, Alex.
Alexander C. Le Dain, PhD
ICON Technologies Pty Ltd
http://www.icon-tech.com.au