DOCUMENT:Q105932  24-MAR-2000  [fortran]
TITLE   :FIX: String Concatenation May Cause Memory Errors
PRODUCT :Microsoft Fortran Compiler
PROD/VER::1.0,1.0a
OPER/SYS:
KEYWORDS:

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft FORTRAN PowerStation for MS-DOS, versions 1.0, 1.0a 
-------------------------------------------------------------------------------

SYMPTOMS
========

Character string concatenations that involve the automatic creation of temporary
variables may cause the following memory related run-time problems:

 - Very slow execution of the application

 - F6700

 - DX2010

RESOLUTION
==========

This memory loss can be avoided by assigning the concatenated strings to a
temporary character string variable.

STATUS
======

Microsoft has confirmed this to be a problem in FORTRAN PowerStation version
1.0. This problem has been resolved with FORTRAN PowerStation maintenance
release version 1.0a for MS-DOS.

FORTRAN PowerStation version 1.0 can be differentiated from the maintenance
release version 1.0a by invoking the linker. Typing "link32 | more" from
\F32\BIN directory will show version 2.8 for FORTRAN PowerStation version 1.0,
and it will show version 1.0f for the maintenance release version 1.0a.

MORE INFORMATION
================

The following two sample programs demonstrate a memory loss due to string
concatenation in the argument list. In both of the following examples, using a
temporary variable for the concatenated strings avoids the memory leak.

Sample Code 1
-------------

   C Compile options needed: none
         character*40 c1,c2
         c1 = 'abcd'
         c2 = 'efgh'
         k = 0
         do i=1,500000
           if(c1//c2 .eq. 'Never') k = k + 1
         end do
         end

The code above will run very slowly, and eventually generate:

   run-time error F6700
   - heap space limit exceeded

Sample Code 2
-------------

   C Compile options needed: none
         character fmtout*20,label(1,3)*(9)
         double precision value
         data (label(1,j),j=1,3)/' Label',' Output',' Test'/ 
         data value/3.14159/ 
         fmtout='f10.3'
         write(6,'(3a,''='','//fmtout//')')(label(1,j),j=1,3),value
         end

The above code on execution will generate:

   DOSXMSF : error DX2010: invalid pointer passed to free or realloc :
   0005F0F8h.
   DOSXMSF : error DX2010: invalid pointer passed to free or realloc :
   0005F0F8h.
   Label Output Test = 3.142

The code does run to completion because this type of DOS-extender error is not
fatal.

Additional query words: 1.00 buglist1.00 fixlist1.00a

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword3 kbFORTRANPower100DOS kbFORTRANPower100aDOS
Version           : :1.0,1.0a
Issue type        : kbbug
Solution Type     : kbfix

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2000.