FIX: Incorrect Result Initializing INTEGER*1 Array

ID: Q72920

The information in this article applies to:

Microsoft FORTRAN for MS-DOS, versions 4.0, 4.01, 4.1, 5.0, 5.1
Microsoft FORTRAN for OS/2, versions 4.1, 5.0, 5.1

SYMPTOMS

Programs compiled with Microsoft FORTRAN versions 4.0, 4.01, 4.1, 5.0, and 5.1 that initialize an integer*1 array with negative values (that is, -128 to -1), can give incorrect results when run under MS-DOS or OS/2.

RESOLUTION

Adding an executable statement that uses an element of the array within the DO-LOOP, or disabling loop optimization with /Od, /Odct, or /4Yb when compiling, can prevent the problem from occurring.

STATUS

Microsoft has confirmed this to be a problem in FORTRAN versions 4.0, 4.01, 4.1, 5.0, and 5.1. This problem was corrected in FORTRAN PowerStation.

MORE INFORMATION

The following program examples illustrate the problem:

Initializing array using a DO-LOOP.


      integer*1 arr(2)
      do 10 i=1,2
        arr(i) = -1
10    continue
      write(*,*) arr(1)
      write(*,*) arr(2)
      end

Initializing array using a single assignment statement (Microsoft FORTRAN versions 5.0 and 5.1 only).


      integer*1 arr(2)
      arr = -1
      write(*,*) arr(1)
      write(*,*) arr(2)
      end

The programs above produce the following output:

-1
-2

The following output should be produced:

-1
-1

To prevent the problem from occurring, add an executable statement that uses an element of the array within the DO-LOOP, or disable loop optimization with /Od, /Odct, or /4Yb when compiling.

Additional query words: 5.00 5.10

Keywords :
Version : :4.0,4.01,4.1,5.0,5.1
Platform :
Issue type :