Re: [LIP] Query:tcsetattr on disk file descriptor and free function issue.

On Mon, 2004-01-19 at 13:16, Binand Sethumadhavan wrote:
> On Mon, 2004-01-19 at 12:27, Shehjar Tikoo wrote:
> > Should'nt the fprintf statement below cause a
> > segmentation fault:
> > 
> > freepthead(head);
> > fprintf(stdout,"%s\n",head->path);

I think in your case by trying to free it in a function you are probably
not doing what you want to do. Read below for what mistake you may be
doing, which Binand probably overlooked.

On Mon, 2004-01-19 at 13:16, Binand Sethumadhavan wrote:
> Not necessarily. OTOH, if your freepthead() function were like:
> 
> free(head);
> head = NULL;
> 
> then this will certainly dump core ("Dereferencing a null pointer").

This may not set the value of head to "0" as "head" is a local variable
in the function freepthead(). In order to set "head" to "0" use as
follows:

void
freepthead(struct pthead **h) /* notice the pointer to pointer */
{
	...
	free(*h);
	*h = 0;
}

Then your call

freepthead(&head); /* notice the pointer to head */
fprintf(stdout,"%s\n",head->path);

will guarantee a segmentation fault.

Regards.
-- 
Josy P. Pullockara <[email protected]>
National Aerospace Laboratories



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