On Wed, 2011-06-22 at 02:37 +0400, Dmitry V. Levin wrote:
> On Tue, Jun 21, 2011 at 08:21:26PM +0200, Denys Vlasenko wrote:
> > Hi,
> >
> > Sometime ago expand_tcbtab/alloc_tcb were modified
> > so that they never return failure (they will abort instead).
> >
> > This opens up a possibility for further simplifications.
> >
> > This patch is a simple one which gets rid of a few
> > intermediate variables, simplifies a few expressions,
> > and uses error_msg_and_die instead of more verbose
> > fprintf+cleanup+exit sequence.
> >
> > In alloc_tcp, I use memset to clear entire new tcp.
> > This not only saves a few bytes of code, but lowers chances
> > of future bugs where some data "leaks out" into new tcb's
> > from old ones because we forgot to re-initialize it.
> >
> > Patch should be fairly safe, but please review anyway.
> > --
> > vda
> >
> > diff -d -urpN strace.6/strace.c strace.7/strace.c
> > --- strace.6/strace.c 2011-06-21 20:12:03.206604267 +0200
> > +++ strace.7/strace.c 2011-06-21 20:11:27.220751557 +0200
> > @@ -1252,21 +1252,14 @@ expand_tcbtab(void)
> > callers have pointers and it would be a pain.
> > So tcbtab is a table of pointers. Since we never
> > free the TCBs, we allocate a single chunk of many. */
> > - struct tcb **newtab = (struct tcb **)
> > - realloc(tcbtab, 2 * tcbtabsize * sizeof tcbtab[0]);
> > - struct tcb *newtcbs = (struct tcb *) calloc(tcbtabsize,
> > - sizeof *newtcbs);
> > - int i;
> > - if (newtab == NULL || newtcbs == NULL) {
> > - fprintf(stderr, "%s: expand_tcbtab: out of memory\n",
> > - progname);
> > - cleanup();
> > - exit(1);
> > - }
> > - for (i = tcbtabsize; i < 2 * tcbtabsize; ++i)
> > - newtab[i] = &newtcbs[i - tcbtabsize];
> > + int i = tcbtabsize;
> > + struct tcb *newtcbs = calloc(tcbtabsize, sizeof newtcbs[0]);
> > tcbtabsize *= 2;
> > - tcbtab = newtab;
> > + tcbtab = realloc(tcbtab, tcbtabsize * sizeof tcbtab[0]);
>
> No, this intermediate newtab is still necessary because cleanup() uses
> tcbtab. For the same reason, tcbtabsize could be changed only when
> tcbtab is already updated, e.g.
> tcbtab = newtab;
> tcbtabsize = newtabsize;
Yes. This should be better:
+ int i = tcbtabsize;
+ struct tcb *newtcbs = calloc(tcbtabsize, sizeof newtcbs[0]);
+ struct tcb **newtab = realloc(tcbtab, tcbtabsize * 2 * sizeof
tcbtab[0]);
+ if (newtab == NULL || newtcbs == NULL)
+ error_msg_and_die("expand_tcbtab: out of memory");
tcbtabsize *= 2;
tcbtab = newtab;
+ while (i < tcbtabsize)
+ tcbtab[i++] = newtcbs++;
--
vda
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