DOCUMENT:Q153005  04-AUG-2001  [visualc]
TITLE   :PRB: Longjmp Inside a _try Block Fails on PowerPC
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:
OPER/SYS:
KEYWORDS:kbVC kbHWPowerPC

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

 - The C/C++ Compiler (CL.EXE), included with:
    - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, version 4.1, on platform(s):
       - the hardware: PowerPC Processor 
-------------------------------------------------------------------------------

SYMPTOMS
========

A program that contains a longjmp called inside a _try block may not call a
_finally block. The sample code below is verified to work consistently on Alpha,
MIPS and Intel platforms. It fails only on Power PC.

WORKAROUND
==========

The solution is to include the setjmpex.h file instead of setjmp.h. The latter
provides consistent behavior on all platforms, but may cause a performance
degradation. Note: either setjmp.h or setjmpex.h may be included, but not both,
because each defines the setjmp macro in a different way.

STATUS
======

This behavior is by design.

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

The on-line documentation claims the following:

   "Exiting a try-finally statement using a return statement or the longjmp
   run-time function is considered abnormal termination. It is illegal to jump
   into a __try statement, but legal to jump out of one."

Consequently, a longjmp within a _try block should cause the _finally to be
executed.

Sample Code
-----------

      /* Compile options needed:
      */ 

      #include <stdio.h>
      #include <stdlib.h>
      //#include <setjmpex.h>  // uncomment this line for the workaround
      #include <setjmp.h> // comment this line out for the workaround
      #include <windows.h>

      CRITICAL_SECTION    cs;
      jmp_buf             jmpbuf;

      void main()
      {
           int  i = 0, j;
           int  hits = 0;

           if(setjmp(jmpbuf))
           {
                hits += 1;
                i = 0;
                printf("\n\n Jump.....\n\n");
           }

           while(1)
           {
                for(j = 0; j < 10; j++)
                     printf("%d ", i++);
                _try
                {
                     longjmp(jmpbuf, 1);
                }
                _finally
                {
                     printf("\n\nInside finally....\n");
                }
           }
      }

Additional query words:

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Keywords          : kbVC kbHWPowerPC 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : winnt:
Issue type        : kbprb

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

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