OK, thanks!
Dimitry Andric <dimi...@andric.com> wrote:
> Ah sorry, I did indeed rebuild grep with --with-included-regex, and for
> debugging purposes added CFLAGS="-O0 -g".
>
> In any case, the problematic code is both in glibc and grep, as I
> believe these are originating from the same source.
>
> -Dimitry
>
> > On 2 Apr 2023, at 08:52, arn...@skeeve.com wrote:
> >
> > Hi.
> >
> > Dimitry Andric <dimi...@andric.com> wrote:
> >
> >> Yes, it still reproduces when I configure the latest grep using
> >> --without-included-regex:
> >
> > I assume you meant --with-included-regex?
> >
> > If you really used --without-included-regex, that doesn't prove anything...
> > :-)
> >
> > It's interesting, as gawk uses the same regex, but with different flags.
> > It might be worth trying to understand which of the syntax bits
> > is causing this.
> >
> > Thanks,
> >
> > Arnold
> >
> >>
> >> 1400 for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
> >> 1: idx = 0
> >> (gdb)
> >> 1402 update_regs (dfa, pmatch, prev_idx_match, cur_node, idx,
> >> nmatch);
> >> 1: idx = 0
> >> (gdb)
> >> 1404 if ((idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
> >> 1: idx = 0
> >> (gdb)
> >> 1405 || (fs && re_node_set_contains (&eps_via_nodes,
> >> cur_node)))
> >> 1: idx = 0
> >> (gdb)
> >> 1428 cur_node = proceed_next_node (mctx, nmatch, pmatch,
> >> prev_idx_match,
> >> 1: idx = 0
> >> (gdb)
> >> 1432 if (__glibc_unlikely (cur_node < 0))
> >> 1: idx = 0
> >> (gdb)
> >> 1400 for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
> >> 1: idx = 0
> >> (gdb)
> >> 1402 update_regs (dfa, pmatch, prev_idx_match, cur_node, idx,
> >> nmatch);
> >> 1: idx = 0
> >> (gdb)
> >> 1404 if ((idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
> >> 1: idx = 0
> >> (gdb)
> >> 1405 || (fs && re_node_set_contains (&eps_via_nodes,
> >> cur_node)))
> >> 1: idx = 0
> >>
> >> The endless loop looks the same. grep's regexec.c is mostly the same as
> >> glibc's, except for the latter having a bunch of #if RE_ENABLE_I18N
> >> directives added.
> >>
> >> -Dimitry
> >>
> >>> On 28 Mar 2023, at 08:46, arn...@skeeve.com wrote:
> >>>
> >>> This does not reproduce with gawk, even when I force use of the regex
> >>> matcher.
> >>>
> >>> What happens if grep is built with the included regex files instead of
> >>> relying on the ones in the local glibc?
> >>>
> >>> Arnold
> >>>
> >>> Dimitry Andric <dimi...@andric.com> wrote:
> >>>
> >>>> On 27 Mar 2023, at 11:14, Koen Claessen <k...@chalmers.se> wrote:
> >>>>>
> >>>>> Running the command:
> >>>>>
> >>>>> echo a | grep -E -w '((()|a)|())*'
> >>>>>
> >>>>> does not terminate, and uses a LOT of processor time, for all versions
> >>>>> of
> >>>>> grep I have tried.
> >>>>>
> >>>>> This is the smallest case that could be found; simplifying anything in
> >>>>> the
> >>>>> input and/or expression leads to correct behavior.
> >>>>
> >>>> Reproducible with GNU grep 3.7 on Ubuntu 22:
> >>>>
> >>>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
> >>>> COMMAND
> >>>> 93938 dim 20 0 9.0m 2.1m 2.0m R 100.0 0.0 0:08.32
> >>>> grep -E -w ((()|a)|())*
> >>>>
> >>>> It seems that at least on Ubuntu, grep in this mode uses glibc's
> >>>> regexec(3), and it is that implementation which ends up in an endless
> >>>> loop.
> >>>>
> >>>> It loops between lines 1415, 1417 and 1443, but idx and cur_node never
> >>>> change from 0:
> >>>>
> >>>> 1378 static reg_errcode_t
> >>>> 1379 __attribute_warn_unused_result__
> >>>> 1380 set_regs (const regex_t *preg, const re_match_context_t *mctx,
> >>>> size_t nmatch,
> >>>> 1381 regmatch_t *pmatch, bool fl_backtrack)
> >>>> 1382 {
> >>>> ...
> >>>> 1415 for (idx = pmatch[0].rm_so; idx <= pmatch[0].rm_eo ;)
> >>>> 1416 {
> >>>> 1417 update_regs (dfa, pmatch, prev_idx_match, cur_node, idx,
> >>>> nmatch);
> >>>> 1418
> >>>> 1419 if ((idx == pmatch[0].rm_eo && cur_node == mctx->last_node)
> >>>> 1420 || (fs && re_node_set_contains (&eps_via_nodes,
> >>>> cur_node)))
> >>>> ...
> >>>> 1442 /* Proceed to next node. */
> >>>> 1443 cur_node = proceed_next_node (mctx, nmatch, pmatch,
> >>>> prev_idx_match,
> >>>> 1444 &idx, cur_node,
> >>>> 1445 &eps_via_nodes, fs);
> >>>> 1446
> >>>> 1447 if (__glibc_unlikely (cur_node < 0))
> >>>> ...
> >>>> 1465 }
> >>>> 1466 }
> >>>>
> >>>> -Dimitry
> >>>>
> >>>> P.S.: Interestingly this does not reproduce with BSD grep, which returns
> >>>> immediately with "a".
> >>>>
> >>
>
