FIX: F1001: confold.c Line 253, Negative Integer Exponent

MS-DOS     | WINDOWS NT

The information in this article applies to:

• Microsoft FORTRAN PowerStation for MS-DOS version 1.0 and 1.0a
• Microsoft FORTRAN PowerStation 32 version 1.0

SYMPTOMS

An attempt to compile an application fails and Microsoft FORTRAN PowerStation version 1.0 for MS-DOS displays the following message:

   fatal error F1001: INTERNAL COMPILER ERROR
      (compiler file '@(#)confold.c:1.144', line 253)
      Contact Microsoft Product Support Services

   fatal error F1001: INTERNAL COMPILER ERROR
      (compiler file '@(#)confold.c:1.144', line 254)
      Contact Microsoft Product Support Services

CAUSE

The command line specifies the /Ox optimization and the code contains an expression that computes a negative integer power of a constant integer or of an integer expression. The error above occurs when the compiler processes the unary minus operator in an integer exponentiation expression.

RESOLUTION

There are two methods to work around this problem:

• Modify the compiler command line to specify the /Oxp compiler option switch.
• Modify the source code to remove the unary minus operator from integer expressions used as exponents. Assign the exponent to a temporary variable and negate the value. Then specify the temporary as the exponent.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was fixed in FORTRAN PowerStation 32, version 4.0.

MORE INFORMATION

The following sample code demonstrates this problem:

Sample Code #1

c Compiler options needed: /Ox

      program test
      integer j
      real    x

      j = 1
      x = 2**(-j)
      print *, x
      end

Sample Code #2

c Compile options needed: /Ox

      program test
      integer j
      real    x

      j = 1
      j = -j      ! Negation occurs here.
      x = 2**(j)
      print *, x
      end