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Q150134: BUG: FOR4165 Warning Underflow of Smallest Positive REAL*8

Article: Q150134
Product(s): Microsoft Fortran Compiler
Version(s): 4.0
Operating System(s): 
Keyword(s): kbFortranPS kbLangFortrankbbuglist
Last Modified: 02-NOV-1999

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The information in this article applies to:

- Microsoft Fortran PowerStation for Windows 95 and Windows NT, version 4.0 
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SYMPTOMS
========

Compiling a source file that contains an assignment of the smallest positive
REAL*8 literal constant to a REAL*8 or DOUBLE PRECISION variable causes the
following compiler warning message:

  warning FOR4165: underflow in REAL literal constant 2.225073858507201D-308

RESOLUTION
==========

Use the TINY() intrinsic function to convert a number to the smallest positive
REAL*8 value, and then use the result in your calculations.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft 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
================

Sample Code to Illustrate Problem and Workaround
------------------------------------------------

  C Compile options needed: none

        REAL*8 dx
        DOUBLE PRECISION dy
        dx = 2.225073858507201D-308  ! Warning - 0.000000000000000 assumed
        write (*,*) dx
        dy = tiny(1.d0)   ! work-around - dy = 2.225073858507201d-308
        write (*,*) dy
        END

Program Output
--------------

  0.000000000000000E+000
  2.225073858507201E-308

Additional query words: 4.00

======================================================================
Keywords          : kbFortranPS kbLangFortran kbbuglist
Technology        : kbAudDeveloper kbPTProdChange kbFortranSearch kbFORTRANPower400NT
Version           : :4.0

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