FIX: F2124 or Incorrect Results From Structure Array Use

ID: Q72760

The information in this article applies to:

Microsoft FORTRAN for OS/2, versions 5.0, 5.1
Microsoft FORTRAN 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 :
Version : :5.0,5.1
Platform :
Issue type :