Function re_search_internal

compat/regex/regexec.c:615–937

   Return REG_NOERROR if we find a match, and REG_NOMATCH if not,
   otherwise return the error code.
   Note: We assume front end functions already check ranges.
   (START + RANGE >= 0 && START + RANGE <= LENGTH)  */

static reg_errcode_t
re_search_internal (const regex_t *preg,
		    const char *string,
		    int length, int start, int range, int stop,
		    size_t nmatch, regmatch_t pmatch[],
		    int eflags)
{
  reg_errcode_t err;
  const re_dfa_t *dfa = (const re_dfa_t *) preg->buffer;
  int left_lim, right_lim, incr;
  int fl_longest_match, match_first, match_kind, match_last = -1;
  int extra_nmatch;
  int sb, ch;
#if defined _LIBC || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L)
  re_match_context_t mctx = { .dfa = dfa };
#else
  re_match_context_t mctx;
#endif
  char *fastmap = (preg->fastmap != NULL && preg->fastmap_accurate
		   && range && !preg->can_be_null) ? preg->fastmap : NULL;
  RE_TRANSLATE_TYPE t = preg->translate;

#if !(defined _LIBC || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
  memset (&mctx, '\0', sizeof (re_match_context_t));
  mctx.dfa = dfa;
#endif

  extra_nmatch = (nmatch > preg->re_nsub) ? nmatch - (preg->re_nsub + 1) : 0;
  nmatch -= extra_nmatch;

  /* Check if the DFA haven't been compiled.  */
  if (BE (preg->used == 0 || dfa->init_state == NULL
	  || dfa->init_state_word == NULL || dfa->init_state_nl == NULL
	  || dfa->init_state_begbuf == NULL, 0))
    return REG_NOMATCH;

#ifdef DEBUG
  /* We assume front-end functions already check them.  */
  assert (start + range >= 0 && start + range <= length);
#endif

  /* If initial states with non-begbuf contexts have no elements,
     the regex must be anchored.  If preg->newline_anchor is set,
     we'll never use init_state_nl, so do not check it.  */
  if (dfa->init_state->nodes.nelem == 0
      && dfa->init_state_word->nodes.nelem == 0
      && (dfa->init_state_nl->nodes.nelem == 0
	  || !preg->newline_anchor))
    {
      if (start != 0 && start + range != 0)
	return REG_NOMATCH;
      start = range = 0;
    }

  /* We must check the longest matching, if nmatch > 0.  */