BUG: Access Violation/Hang on Divide by Zero with Intrinsic

• Microsoft FORTRAN PowerStation 32 for Windows NT, version 1.0

SYMPTOMS

The following error may not be produced when a divide by zero exception involving an intrinsic function occurs at run time:

   run-time error M6103: MATH
   floating-point error: divide by 0

The following occurs using Fortran PowerStation 32, version 4.0:

1. Using the -Ox compile option causes an Application Error at run-time.

2. Using no compile options, the following appropriate run-time error is generated:

   run-time error M6103: MATH - floating-point error: divide by zero

CAUSE

This unexpected behavior occurs when the divide by zero exception occurs in the argument list of the SIN, COS, or SQRT intrinsic functions. ABS, EXP, and TAN also produce incorrect behavior that is slightly different from the behavior mentioned above.

RESOLUTION

Explicitly check denominators in arguments to the SIN, COS, TAN, ABS, EXP, or SQRT intrinsic function for zero values before performing a divide operation.

STATUS

Microsoft has confirmed this to be a problem in the products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The intrinsic function ABS generates the appropriate run-time error regardless of optimization.

The intrinsic function EXP generates the appropriate run-time error with -Ox, and hangs otherwise.

The intrinsic function TAN returns 0 (zero) with -Ox, and hangs otherwise. For this particular function, the compiler may generate the following warning when compiling with /Ox:

   warning F4723: potential divide by 0

Sample Code

C Compile options needed: -Ox causes an Application Error to occur C Compile options needed: none causes the application to hang

      a = 0.
      b = 1.
      write (*,*) a,b !no effect when commented out
      c= SQRT(b/a) !GPF here

      write (*,*) a,b,c  !no effect when commented out
      end