Re: [rfc] Prompt memory management/cleanups

[Pedro Alves <pedro at codesourcery dot com>]

On Wednesday 20 July 2011 16:04:16, Phil Muldoon wrote:
> Pedro Alves <pedro@codesourcery.com> writes:
> 
> > On Wednesday 20 July 2011 15:30:19, Phil Muldoon wrote:
> >> s = get_prompt (0)
> >> set_prompt (s, 0)
> >> 
> >> Without that check, 'PROMPT (level)' would be freed, but 's' points to
> >> that.  So you set garbage.   get_prompt returns a pointer, not a copy.
> >
> > I'm probably missing something, but isn't it just
> > a matter of instead of having:
> >
> > +       xfree (PROMPT (level));
> > +       PROMPT (level) =  xstrdup (s);
> >
> > you have:
> >
> > +		 char *newp = xstrdup (s);
> > +       xfree (PROMPT (level));
> > +       PROMPT (level) = newp;
> >
> > ?
> 
> Yeah I noted we could do that in my reply.  Sure we can do that, I'm not
> opposed to it.  But I am not sure on your objection to the check we make
> first instead of the xstrdup?  If PROMPT (level) == s, then there is no
> need to copy the contents of s into PROMPT, it is already there?  The
> user is effectively asking for a noop?

You've asked for comments on the API, and IMO this makes for
a weird API, because the caller of set_prompt needs to know
whether set_prompt will take ownership of the pointer or not
depending on where the pointer came from.  I haven't looked
at the callers -- that's why I asked what would need to
change.  :-)

-- 
Pedro Alves