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Incorrect result of Present

 
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simon



Joined: 05 Jul 2006
Posts: 268

PostPosted: Mon May 16, 2022 11:01 am    Post subject: Incorrect result of Present Reply with quote

FTN95 fails to identify that the optional argument, i, in f2 is not present. I believe that the code is invalid Fortran, and that the External declaration in line 3 needs to be replaced by the commented-out Interface. As it is, FTN95 indicates that the optional argument, i, is present, whereas other compilers generate a run-time error. The argument i is correctly indicated as not present if the interface block is used.
!
Code:
Module m1
Contains
 Function f1(f)
   Integer :: f1
   Integer, External :: f
!   Interface
!    Function f(i)
!     Integer :: f
!     Integer, Intent(In), Optional :: i
!    End Function f
!   End Interface
!
   f1 = f()
   Return
 End Function f1
End Module m1
!
Module m2
Contains
 Function f2(i)
   Integer :: f2
   Integer, Intent(In), Optional :: i
!
   print*,Present(i)
   f2 = 0
!
   Return
 End Function f2
End Module m2
!
Program p
   Use m1
   Use m2
   Integer :: i
   i = f1(f2)
End Program p
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PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 7916
Location: Salford, UK

PostPosted: Mon May 16, 2022 11:22 am    Post subject: Reply with quote

Simon

I am not able to run your code at the moment.

Reading your code, it seems to me that the interface is required. Without the interface the code is not valid and the runtime outcome will be compiler dependent and maybe also random.
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PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 7916
Location: Salford, UK

PostPosted: Mon May 23, 2022 7:01 am    Post subject: Reply with quote

Simon

The interface is required and (when omitted) FTN95 produces a runtime error report when /CHECK is used.
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simon



Joined: 05 Jul 2006
Posts: 268

PostPosted: Mon May 23, 2022 2:19 pm    Post subject: Reply with quote

Understood Paul. Thanks
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