Re: program is not crashing, after 10 iteration

From:
pjb@informatimago.com (Pascal J. Bourguignon)
Newsgroups:
comp.lang.c++
Date:
Mon, 20 Jul 2009 11:22:03 +0200
Message-ID:
<7ck523lnes.fsf@pbourguignon.anevia.com>
Pallav singh <singh.pallav@gmail.com> writes:

Hi All ,

the program is not crashing, after 10 iteration of the loop;

int main( )
   {
      int * ptr = (int *)malloc( 10) ;
      while( 1 )
          {
                printf(" %d \n",*ptr);
                ptr++ ;
          }
    }


Check the other discussion "Books for advanced C++ debugging".

This is formally an "undefined behavior" situation.

We plain programmers would like the implementation to throw an
exception when such a situation occurs.

But it would be more work for compiler writters, so they don't want to
provide such a feature (much less optionnaly, since that would be even
more work). And therefore the industry must bear the cost of uncaught
bugs, of which viruses and worms take benefit.

Personnaly, the only solution I see is to forget C and C++ and instead
use implementations of different programming languages that provide
such run-time checks and error detection, be it because the
implementers of these other programming languages are not as stubborn
as C or C++ implementers, or because those other programming languages
define such an error checking behavior.

Just for an example of such another culture, here is what you'd get
with Common Lisp (but most other programming languages detect these
errors):

C/USER[29]> (declaim (optimize (safety 0) (debug 0) (speed 3) (space 2)))
NIL
C/USER[30]> (defun main ()
              (let ((ptr (make-array 10 :element-type 'integer :initial-element 0)))
                (loop for i from 0 do (format t " ~D ~^" (aref ptr i)))))
MAIN
C/USER[31]> (main)
 0 0 0 0 0 0 0 0 0 0
*** - AREF: index 10 for #(0 0 0 0 0 0 0 0 0 0) is out of range
The following restarts are available:
ABORT :R1 Abort main loop
C/Break 1 USER[32]>

--
__Pascal Bourguignon__

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