Re: Reentrancy

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 9 Apr 2009 11:19:56 -0400

Message-ID:

<uYHFlaSuJHA.1240@TK2MSFTNGP02.phx.gbl>

Krat <kursattheking@gmail.com> wrote:

The wikipedia
article(http://en.wikipedia.org/wiki/Reentrant_(subroutine)) that
defines "reentrant" gives 6 rules to write reentrant code. According
to the definition a function like this is reentrant :
char reentrant_func (char * ptr)
{
   return *(ptr + 2);
}

CALL-2

char * buf = 0;

int main ()
{
   buf = (char * ) malloc (256);
   strcpy (buf, "Reentrant");

   char c = reentrant_func (buf);
}

In call-2 we supplied a pointer to a global data so the function call
may not be reentrant.

A function can be reentrant or not. It's meaningless to say that a
particular function call is reentrant or not - you can't make the same
call twice.

In any case, in what sense is the situation you show non-reentrant? Does
the function not successfully return the third character of the
passed-in buffer? Will it not continue to do so even if called
concurrently?

So I think "not only functions but also
function calls should be reentrant".

Define "reentrant function call". I'm not familiar with the term.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925