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Q72760: FIX: F2124 or Incorrect Results From Structure Array Use

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Article: Q72760
Product(s): Microsoft Fortran Compiler
Version(s): 5.0,5.1
Operating System(s): 
Keyword(s): 
Last Modified: 04-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft FORTRAN compiler for OS/2, versions 5.0, 5.1 
- Microsoft FORTRAN Compiler for MS-DOS, versions 5.0, 5.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

An attempt to compile an application fails and the compiler may generate the
following message:

  F2124: CODE GENERATION ERROR
  Contact Microsoft Technical Support

Alternately, the application compiles without error but does not generate any
output.

CAUSE
=====

The application declares an array of structures that contain REAL*4 elements,
REAL*8 elements, or mixed-type elements (for example, one INTEGER*4 element and
one COMPLEX*8 element). The application attempts to write the entire array
without specifying a subscript.

The same code generation error can occur if the application declares an
assumed-size array in a subprogram and the compiler command line specifies the
/Od compiler option switch. In this case, the types of the structure elements do
not effect the error. If the command line does not include /Od compiler option
switch, the error message may not appear, but the application does not produce
any output.

Neither the ANSI FORTRAN 77 standard nor Microsoft FORTRAN supports printing an
entire assumed-size array. The compiler is designed to generate the following
error message in this case:

  F2727: assumed-size array illegal here

RESOLUTION
==========

To address this error, modify the source code to print each element of the array
individually instead of all at once.

STATUS
======

Microsoft has confirmed this to be a problem in FORTRAN versions 5.0 and 5.1 for
MS-DOS and OS/2. This problem was corrected in FORTRAN PowerStation, version
1.0.

MORE INFORMATION
================

The following code example demonstrates this problem.

Sample Code #1
--------------

  C Compile options needed: None

        STRUCTURE /STRUC/ 
          REAL R
        END STRUCTURE
        RECORD /STRUC/ S(10)
        S.R = 4
        WRITE (*, *) S.R
        END

To work around this problem, use an implied-DO loop to print each elements of the
array of structures. The following code example demonstrates this approach.

Sample Code #2
--------------

  C Compile options needed: None

        STRUCTURE /STRUC/ 
          REAL R
        END STRUCTURE
        RECORD /STRUC/ S(10)
        S.R = 4
        WRITE (*, *) (S(I).R, I = 1, 10) ! Print elements using
                                         ! implied DO-loop
        END

The following code example, that uses an assumed-size array of structures,
compiles without error but does not produce any output.

Sample Code #3
--------------

  C Compile options needed: None

        STRUCTURE /STRUC/ 
         REAL R
        END STRUCTURE
        RECORD /STRUC/ ST(10)
        ST.R = 4
        CALL SUB(ST)
        END

        SUBROUTINE SUB(ST)
        STRUCTURE /STRUC/ 
         REAL R
        END STRUCTURE
        RECORD /STRUC/ ST(*)   ! Assumed-sized array declared
        WRITE (*, *) ST.R      ! nothing is output here
        END

Compiling this code example with the /Od compiler option switch specified causes
a code generation error.

An application cannot print an assumed-size array as an array. The application
must specify a subscript and print each element individually. One solution to
this problem is to use an adjustable- sized array. Pass the length of the
structure array to the subprogram with the array itself. Use the array length to
terminate the loop that prints the individual array elements. The following code
example demonstrates this process.

Sample Code #4
--------------

  C Compile options needed: None

        PARAMETER (LENGTH = 10)
        STRUCTURE /STRUC/ 
         REAL J
        END STRUCTURE
        RECORD /STRUC/ ST(LENGTH)
        ST.J = 4
        CALL SUB(ST, LENGTH)
        END

        SUBROUTINE SUB(ST, LENGTH)
        STRUCTURE /STRUC/ 
         REAL J
        END STRUCTURE
        INTEGER LENGTH
        RECORD /STRUC/ ST(LENGTH)
        WRITE (*, *) (ST(I).J, I = 1, LENGTH)  ! Print array elements
                                               ! in implied DO-loop
        END

Additional query words: 5.00 5.10 buglist5.00 buglist5.10 fixlist1.00

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword3 kbFORTRAN510DOS kbFORTRAN500DOS kbFORTRAN500OS2 kbFORTRAN510OS2
Version           : :5.0,5.1
Issue type        : kbbug
Solution Type     : kbfix

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