FIX: No F6099 with /4I2 and /4Yb on Integer Overflow

MS-DOS                   | OS/2

The information in this article applies to:

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

SYMPTOMS

Programs compiled with the $STORAGE:2 metacommand, the /4I2 option and $DEBUG metacommand, or the /4Yb option, with integer variables taking values beyond their full 16-bit range (-32,768 to 32,767), may not generate the following error:

   Run-Time Error F6099: $DEBUG
         INTEGER overflow

CAUSE

The $STORAGE:2 metacommand, /4I2 option and $DEBUG metacommand, or the /4Yb option does not cause the compiler to generate additional code that will lead to a jump to the overflow routine for integer values that are out of range. This incorrect code generation is due to the common subexpression elimination optimization.

RESOLUTION

To correctly generate this error message for integer values that are out of the integer*2 (16-bit) range, compile with the /Od switch to disable optimization. Optimization may be partially turned back on with the optimization switches: /Os, /Ot, and /Ol (which do not enable common subexpression elimination /Oc).

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, version 1.0.

MORE INFORMATION

The following code does generate the F6099 error if compiled with the partial optimization of /Odlt, but will not generate the error if complied with either the default full optimization "/Ox" or common subexpression elimination "/Odc":

Sample Code

$debug $storage:2

      integer*2 i,j,k

      i=10
      j=4000
      k=i*j
      end