Microsoft KB Archive/153005

= PRB: Longjmp Inside a _try Block Fails on PowerPC =

Article ID: 153005

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 4.1 Subscription

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This article was previously published under Q153005



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   #include    //#include   // uncomment this line for the workaround #include  // comment this line out for the workaround #include 

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"); }       }   }

Keywords: kbprb KB153005

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