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Re: Would someone tell me if I'm on the wrong track?

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luser- -droog wrote:
> 
> On May 11, 1:31 am, "io_x" <a...@b.c.invalid> wrote:
> > "luser- -droog" <mijo...@yahoo.com> ha scritto nel messaggionews:70cf2865-5c4a-47a5-a8e8-ac369c2b91b3@k22g2000yqh.googlegroups.com...
> >
> >
> >
> > > I'm trying to build a new memory allocation scheme for
> > > my postscript interpreter to satisfy these requirements:
> > > % pointer + offset + size + short tag <= 32bits
> > > % 'garbage-collection'-ready (structure the heap for easy iteration)
> > > % all memory is in one region for easy restore from disk
> >
> > > So I've written a prototype where the "pointer" is an index
> > > into an extendable address table stored in the heap itself.
> > > And it seems to work! But I don't trust it, you know?
> >
> > > I'd appreciate any comments the experts here could offer.
> >
> [...]
> > > /* grow memory by sz */
> > > void growmem(mfile *mem, unsigned sz) {
> > >    unsigned char *tmp;
> > >    if (sz < pgsz) sz = pgsz;
> > >    else sz = (sz/pgsz + 1) * pgsz;
> >
> > what about if this mult above overflow?
> >
> > >    sz += mem->max;
> >
> > what about if this sz += overflow?
> > i not understand well the remain (too much complex
> > for my little think)
> > but i think, it is better to see if sz overflow
> > and in input to write "if((int) sz <0)  return  -1;"
> > so that each function can fail.
> > never exist one function can not fail
> 
> unsigned sz;
> (int) sz < 0
> 
> Does this just check the high bit (assuming 2's complement)?

I don't know, 
but I don't see the relevance of ((int) sz < 0).

If you want to check for wrap around after (sz += mem->max), then 

    if (sz - mem->max > sz) ThenItWrapped;

-- 
pete

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Would someone tell me if I'm on the wrong track? luser- -droog <mijoryx@yahoo.com> - 2011-05-09 23:47 -0700
  Re: Would someone tell me if I'm on the wrong track? luser- -droog <mijoryx@yahoo.com> - 2011-05-10 00:05 -0700
  Re: Would someone tell me if I'm on the wrong track? "io_x" <a@b.c.invalid> - 2011-05-11 08:31 +0200
    Re: Would someone tell me if I'm on the wrong track? luser- -droog <mijoryx@yahoo.com> - 2011-05-10 23:46 -0700
    Re: Would someone tell me if I'm on the wrong track? luser- -droog <mijoryx@yahoo.com> - 2011-05-11 23:05 -0700
      Re: Would someone tell me if I'm on the wrong track? Seebs <usenet-nospam@seebs.net> - 2011-05-12 07:36 +0000
        Re: Would someone tell me if I'm on the wrong track? pete <pfiland@mindspring.com> - 2011-05-12 07:51 -0400
        Re: Would someone tell me if I'm on the wrong track? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-05-14 03:34 +0100
          Re: Would someone tell me if I'm on the wrong track? pete <pfiland@mindspring.com> - 2011-05-13 23:19 -0400
            Re: Would someone tell me if I'm on the wrong track? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-05-14 12:02 +0100
      Re: Would someone tell me if I'm on the wrong track? pete <pfiland@mindspring.com> - 2011-05-12 08:01 -0400
        Re: Would someone tell me if I'm on the wrong track? Seebs <usenet-nospam@seebs.net> - 2011-05-12 15:57 +0000
          Re: Would someone tell me if I'm on the wrong track? pete <pfiland@mindspring.com> - 2011-05-12 18:04 -0400
            Re: Would someone tell me if I'm on the wrong track? Seebs <usenet-nospam@seebs.net> - 2011-05-12 22:18 +0000
            Re: Would someone tell me if I'm on the wrong track? luser- -droog <mijoryx@yahoo.com> - 2011-05-12 23:05 -0700
              Re: Would someone tell me if I'm on the wrong track? "io_x" <a@b.c.invalid> - 2011-05-13 10:21 +0200
        Re: Would someone tell me if I'm on the wrong track? luser- -droog <mijoryx@yahoo.com> - 2011-05-12 09:33 -0700
      Re: Would someone tell me if I'm on the wrong track? Peter Nilsson <airia@acay.com.au> - 2011-05-12 22:47 -0700
        Re: Would someone tell me if I'm on the wrong track? "io_x" <a@b.c.invalid> - 2011-05-13 10:21 +0200
        Re: Would someone tell me if I'm on the wrong track? Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-18 22:21 -0700
          Re: Would someone tell me if I'm on the wrong track? Peter Nilsson <airia@acay.com.au> - 2011-05-18 23:47 -0700
            Re: Would someone tell me if I'm on the wrong track? Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 11:00 -0700

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