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Keith Waters
Joined: 07 Aug 2007
Posts: 29
Location: London or Somerset, UK
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 Posted: Thu Aug 09, 2007 9:22 am Post subject: Undefined variable error/bug with user defined type |
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I’m getting the following run-time error in one of my Win32 programs and I cannot see why.
*** Error 112, Reference to undefined variable, array element or function result (/UNDEF)
I’ve constructed a small program that demonstrates the error and consists of a Main and two Modules as follows.
| Code: | C ------------------------------------------------------------
C DEMO.FOR
PROGRAM DEMO
USE Calc
CALL WX_AddErrors () !<<<<<< Line 13
PRINT *, 'Demo program has run'
END
! -----------------------------------------------------------
MODULE Calc
USE Dict, ONLY: Dictionary_t, &
Dict_Len, &
Dict_reset
PRIVATE
TYPE(Dictionary_t), PRIVATE :: xDic
PUBLIC :: WX_AddErrors
CONTAINS
! ----------------------------------------------------------
SUBROUTINE WX_AddErrors ()
INTEGER(KIND=SELECTED_INT_KIND(9)) :: dLen
! xDic%nItems = 0 !This (uncommented) fixes problem ?!!!
dLen = Dict_Len(xDic) !<<<<<< Line 30
IF (dLen == 0) RETURN
!Processing code goes here (omitted for clarity)
CALL Dict_Reset (xDic)
END SUBROUTINE
END MODULE
! --------------------------------------------------------------
MODULE Dict
PRIVATE
INTEGER(KIND=SELECTED_INT_KIND(9)), PARAMETER, PRIVATE :: MAX_ITEMS = 50
INTEGER(KIND=SELECTED_INT_KIND(9)), PARAMETER, PUBLIC :: DICT_ITEM_LEN = 100
TYPE, PUBLIC :: Dictionary_t
PRIVATE
INTEGER(KIND=SELECTED_INT_KIND(9)) :: nItems = 0
CHARACTER(LEN=DICT_ITEM_LEN), DIMENSION(1: MAX_ITEMS) :: key = ''
CHARACTER(LEN=DICT_ITEM_LEN), DIMENSION(1: MAX_ITEMS) :: value = ''
END TYPE
PUBLIC :: Dict_Reset, &
Dict_Len
CONTAINS
! -----------------------------------------------------
! Resets the dictionary to empty
!
SUBROUTINE Dict_Reset (dict)
TYPE(Dictionary_t), INTENT(INOUT) :: dict
dict%nItems = 0
END SUBROUTINE
!------------------------------------------------------
! Returns number of entries in the dictionary
!
FUNCTION Dict_Len (dict)
INTEGER(KIND=SELECTED_INT_KIND(9)) :: Dict_Len
TYPE(Dictionary_t), INTENT(IN) :: dict
Dict_Len = dict%nItems !<<<<<< Line 45
END FUNCTION
END MODULE
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I’m using a recently downloaded FTN95 Personal Edition, which is declared as version 5.10 on the Polyhedron web site but prints version 4.9.0 on the console. I compile with the options, /ISO /IMPLICIT_NONE /NO_SCALAR_TO_ARRAY /RESTRICT_SYNTAX /CHECKMATE /BRIEF /ERRORLOG and then link with SLINK. The run-time error information is as follows (I’ve flagged the offending line numbers in the above code).
DICT!DICT_LEN - in file dict.f90 at line 45 [+0041]
CALC!WX_ADDERRORS - in file calc.f90 at line 30 [+002c]
main - in file demo.for at line 13 [+0031]
The problem seems to be that the variable, xDic in module Calc, or one of its members, is being seen as uninitialised or undefined. I cannot see how this can be since all the members are initialised at the point of defining the Dictionary_t type in module Dict.
Even stranger is the fact that when I uncomment the statement, “xDic%nItems = 0” in subroutine WX_AddErrors in module Calc, the problem goes away, which seems to confirm that the issue is with initialisation. However, I cannot see how this statement should compile. Surely the compiler should issue an error message here because all the members of xDic are private (see definition of Dictionary_t in module Dict).
I would re |
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PaulLaidler
Site Admin
Joined: 21 Feb 2005
Posts: 7926
Location: Salford, UK
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| Posted: Sat Aug 11, 2007 4:21 pm Post subject: |
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Assuming this is valid Fortran (and I think it is valid) then your code reveals a missing feature in FTN95. Clearly the initialisation as not be implemented by the compiler.
For the moment it will be necessary to do the initialisation as an assignment statement. |
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Keith Waters
Joined: 07 Aug 2007
Posts: 29
Location: London or Somerset, UK
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| Posted: Sat Aug 11, 2007 5:35 pm Post subject: |
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Thanks for replying and I agree. It is not too much of a hassle for me to provide an initialisation routine that must be called before using module Dict or Calc.
I think what really surprised me was FTN95 allowing an assignment (xDic%nItems = 0) to a private member of the Dictionary_t type outside of module Dict. I tried this with an ancient Digital Fortran compiler and got,
Error: The parent type of this field is use associated with the PRIVATE fields attribute [NITEMS]
FTN95 should give some equivalent message. |
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JohnCampbell
Joined: 16 Feb 2006
Posts: 2554
Location: Sydney
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| Posted: Mon Aug 13, 2007 12:26 am Post subject: |
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Is there any requirement to define modules in order, so that they are defined before being used ?
The reverse order in the example code doesn't look right |
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Keith Waters
Joined: 07 Aug 2007
Posts: 29
Location: London or Somerset, UK
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| Posted: Mon Aug 13, 2007 7:05 am Post subject: |
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They are in separately compiled files and the .obj are then linked.
PROGRAM DEMO in demo.for,
MODULE Calc in Calc.f90, and
MODULE Dict in Dict.f90.
Like I say, the program compiles and runs with no error if I include the assignment, xDic%nItems = 0. The problem has nothing to do with order of modules. It is a bug in FTN95. |
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PaulLaidler
Site Admin
Joined: 21 Feb 2005
Posts: 7926
Location: Salford, UK
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| Posted: Mon Aug 13, 2007 1:58 pm Post subject: |
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The initialisation works OK for small arrays (key and value) so this is a bug rather than a missing feature.
The PRIVATE attribute works OK for a main program or external subroutine. Again this is a bug.
We hope to fix both bugs in time for the next release. |
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