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mruby-regexp: keep the pike VM's visited keys from wrapping #7073

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Merged
matz merged 1 commit into from
Aug 10, 2026
Merged

mruby-regexp: keep the pike VM's visited keys from wrapping #7073

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31 changes: 24 additions & 7 deletions mrbgems/mruby-regexp/src/re_exec.c
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,24 @@ pool_copy(pike_state *s, int src_slot)

#define CAP(s, slot) (&(s)->cap_pool[(slot) * (s)->ncap])

/* Hand this step's closure a fresh block of visited keys. A step reserves one
key per epsilon pass, so the counter climbs faster than the single step it
used to; on a long enough subject it would wrap, leaving marks from earlier
steps outranking every fresh key and the closure adding nothing. Clear the
marks and start the keys over when that comes into reach, which also keeps
a live key below RE_LOOP_STOP. */
static void
advance_gen(pike_state *s)
{
if (s->key_max > UINT32_MAX - 2 * s->pass_span) {
memset(s->visited, 0, sizeof(uint32_t) * (s->pat->code_len + 1));
s->gen = 0;
s->key_max = s->pass_span - 1;
}
s->gen += s->pass_span;
s->key_max += s->pass_span;
}

/* TRUE once this step's closure has walked the loop head at pc, which means
the body just ran without consuming: an empty iteration. */
static mrb_bool
Expand All @@ -144,7 +162,8 @@ loop_head_seen(pike_state *s, uint32_t pc)
target's branch walks under, or RE_LOOP_STOP when the body matched empty
and the repetition therefore has to stop. An ordinary fork, or one closing
a loop whose body always consumes (`a` is 0, see mark_empty_loops()), has
no empty iteration to account for and keeps the current key. */
no empty iteration to account for and keeps the current key. advance_gen()
holds every live key below the sentinel. */
#define RE_LOOP_STOP UINT32_MAX

static uint32_t
Expand Down Expand Up @@ -347,8 +366,8 @@ pike_vm(mrb_state *mrb, const mrb_regexp_pattern *pat,
s.binary = binary;
s.cut = FALSE;
s.pass_span = RE_PASS_SPAN(pat->loop_depth);
s.gen = s.pass_span;
s.key_max = s.gen + s.pass_span - 1;
s.gen = 0;
s.key_max = s.pass_span - 1;
if (match_only) {
s.pool_capa = 1;
s.pool_next = 0;
Expand Down Expand Up @@ -404,8 +423,7 @@ pike_vm(mrb_state *mrb, const mrb_regexp_pattern *pat,
!mrb_re_utf8_interior_p(str, sp, str_end)) {
int slot = match_only ? 0 : pool_alloc(&s);
if (!match_only) memset(CAP(&s, slot), -1, sizeof(int) * ncap);
s.gen += s.pass_span;
s.key_max += s.pass_span;
advance_gen(&s);
s.cut = FALSE;
add_thread(&s, &curr, 0, slot, sp, s.gen);
if (s.matched && curr.count == 0) break;
Expand Down Expand Up @@ -435,8 +453,7 @@ pike_vm(mrb_state *mrb, const mrb_regexp_pattern *pat,
s.pool_next = curr.count;
}

s.gen += s.pass_span;
s.key_max += s.pass_span;
advance_gen(&s);
s.cut = FALSE;
next.count = 0;

Expand Down
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