DOCUMENT:Q108409 02-NOV-1999 [fortran] TITLE :BUG: Access Violation/Hang on Divide by Zero with Intrinsic PRODUCT :Microsoft Fortran Compiler PROD/VER::1.0 OPER/SYS: KEYWORDS:kberrmsg kbLangFortran ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - 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 If such a program is compiled with the -Ox option, a Dr. Watson "Application Error" message box specifying "Exception: access violation" may be generated. Otherwise, the application may hang. 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 The following sample code illustrates the symptoms described above: 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 Additional query words: 1.00 4.00 lock halt gp-fault ====================================================================== Keywords : kberrmsg kbLangFortran Technology : kbAudDeveloper kbFortranSearch kbZNotKeyword2 kbFORTRANPower32100NT Version : :1.0 ============================================================================= 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 1999.