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;
--
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