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PATCH: [perl #132851] Empty /(?)/
[perl5.git] / regcomp.c
index 387126e..547b911 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
 #define PERL_IN_REGCOMP_C
 #include "perl.h"
 
-#ifndef PERL_IN_XSUB_RE
-#  include "INTERN.h"
-#endif
-
 #define REG_COMP_C
 #ifdef PERL_IN_XSUB_RE
 #  include "re_comp.h"
@@ -167,6 +163,7 @@ struct RExC_state_t {
     I32                seen_zerolen;
     regnode_offset *open_parens;       /* offsets to open parens */
     regnode_offset *close_parens;      /* offsets to close parens */
+    I32      parens_buf_size;           /* #slots malloced open/close_parens */
     regnode     *end_op;                /* END node in program */
     I32                utf8;           /* whether the pattern is utf8 or not */
     I32                orig_utf8;      /* whether the pattern was originally in utf8 */
@@ -197,6 +194,7 @@ struct RExC_state_t {
     scan_frame *frame_last;
     U32         frame_count;
     AV         *warn_text;
+    HV         *unlexed_names;
 #ifdef ADD_TO_REGEXEC
     char       *starttry;              /* -Dr: where regtry was called. */
 #define RExC_starttry  (pRExC_state->starttry)
@@ -256,6 +254,7 @@ struct RExC_state_t {
 #define RExC_maxlen        (pRExC_state->maxlen)
 #define RExC_npar      (pRExC_state->npar)
 #define RExC_total_parens      (pRExC_state->total_par)
+#define RExC_parens_buf_size   (pRExC_state->parens_buf_size)
 #define RExC_nestroot   (pRExC_state->nestroot)
 #define RExC_seen_zerolen      (pRExC_state->seen_zerolen)
 #define RExC_utf8      (pRExC_state->utf8)
@@ -284,6 +283,7 @@ struct RExC_state_t {
 #define RExC_warn_text (pRExC_state->warn_text)
 #define RExC_in_script_run      (pRExC_state->in_script_run)
 #define RExC_use_BRANCHJ        (pRExC_state->use_BRANCHJ)
+#define RExC_unlexed_names (pRExC_state->unlexed_names)
 
 /* Heuristic check on the complexity of the pattern: if TOO_NAUGHTY, we set
  * a flag to disable back-off on the fixed/floating substrings - if it's
@@ -355,7 +355,7 @@ struct RExC_state_t {
             if (DEPENDS_SEMANTICS) {                                        \
                 set_regex_charset(&RExC_flags, REGEX_UNICODE_CHARSET);      \
                 RExC_uni_semantics = 1;                                     \
-                if (RExC_seen_d_op && LIKELY(RExC_total_parens >= 0)) {     \
+                if (RExC_seen_d_op && LIKELY(! IN_PARENS_PASS)) {           \
                     /* No need to restart the parse if we haven't seen      \
                      * anything that differs between /u and /d, and no need \
                      * to restart immediately if we're going to reparse     \
@@ -366,11 +366,10 @@ struct RExC_state_t {
             }                                                               \
     } STMT_END
 
-#define BRANCH_MAX_OFFSET   U16_MAX
 #define REQUIRE_BRANCHJ(flagp, restart_retval)                              \
     STMT_START {                                                            \
                 RExC_use_BRANCHJ = 1;                                       \
-                if (LIKELY(RExC_total_parens >= 0)) {                       \
+                if (LIKELY(! IN_PARENS_PASS)) {                             \
                     /* No need to restart the parse immediately if we're    \
                      * going to reparse anyway to count parens */           \
                     *flagp |= RESTART_PARSE;                                \
@@ -378,10 +377,19 @@ struct RExC_state_t {
                 }                                                           \
     } STMT_END
 
+/* Until we have completed the parse, we leave RExC_total_parens at 0 or
+ * less.  After that, it must always be positive, because the whole re is
+ * considered to be surrounded by virtual parens.  Setting it to negative
+ * indicates there is some construct that needs to know the actual number of
+ * parens to be properly handled.  And that means an extra pass will be
+ * required after we've counted them all */
+#define ALL_PARENS_COUNTED (RExC_total_parens > 0)
 #define REQUIRE_PARENS_PASS                                                 \
-    STMT_START {                                                            \
-                    if (RExC_total_parens == 0) RExC_total_parens = -1;     \
+    STMT_START {  /* No-op if have completed a pass */                      \
+                    if (! ALL_PARENS_COUNTED) RExC_total_parens = -1;       \
     } STMT_END
+#define IN_PARENS_PASS (RExC_total_parens < 0)
+
 
 /* This is used to return failure (zero) early from the calling function if
  * various flags in 'flags' are set.  Two flags always cause a return:
@@ -698,7 +706,7 @@ static const scan_data_t zero_scan_data = {
 
 /* Used to point after bad bytes for an error message, but avoid skipping
  * past a nul byte. */
-#define SKIP_IF_CHAR(s) (!*(s) ? 0 : UTF ? UTF8SKIP(s) : 1)
+#define SKIP_IF_CHAR(s, e) (!*(s) ? 0 : UTF ? UTF8_SAFE_SKIP(s, e) : 1)
 
 /* Set up to clean up after our imminent demise */
 #define PREPARE_TO_DIE                                                      \
@@ -1560,6 +1568,7 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
      * returned list must, and will, contain every code point that is a
      * possibility. */
 
+    dVAR;
     SV* invlist = NULL;
     SV* only_utf8_locale_invlist = NULL;
     unsigned int i;
@@ -1704,6 +1713,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * another SSC or a regular ANYOF class.  Can create false positives. */
 
     SV* anded_cp_list;
+    U8  and_with_flags = (OP(and_with) == ANYOFH) ? 0 : ANYOF_FLAGS(and_with);
     U8  anded_flags;
 
     PERL_ARGS_ASSERT_SSC_AND;
@@ -1714,7 +1724,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * the code point inversion list and just the relevant flags */
     if (is_ANYOF_SYNTHETIC(and_with)) {
         anded_cp_list = ((regnode_ssc *)and_with)->invlist;
-        anded_flags = ANYOF_FLAGS(and_with);
+        anded_flags = and_with_flags;
 
         /* XXX This is a kludge around what appears to be deficiencies in the
          * optimizer.  If we make S_ssc_anything() add in the WARN_SUPER flag,
@@ -1738,14 +1748,14 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
     else {
         anded_cp_list = get_ANYOF_cp_list_for_ssc(pRExC_state, and_with);
         if (OP(and_with) == ANYOFD) {
-            anded_flags = ANYOF_FLAGS(and_with) & ANYOF_COMMON_FLAGS;
+            anded_flags = and_with_flags & ANYOF_COMMON_FLAGS;
         }
         else {
-            anded_flags = ANYOF_FLAGS(and_with)
+            anded_flags = and_with_flags
             &( ANYOF_COMMON_FLAGS
               |ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER
               |ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP);
-            if (ANYOFL_UTF8_LOCALE_REQD(ANYOF_FLAGS(and_with))) {
+            if (ANYOFL_UTF8_LOCALE_REQD(and_with_flags)) {
                 anded_flags &=
                     ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
             }
@@ -1785,7 +1795,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      *                         <=  (C1 & ~C2) | (P1 & ~P2)
      * */
 
-    if ((ANYOF_FLAGS(and_with) & ANYOF_INVERT)
+    if ((and_with_flags & ANYOF_INVERT)
         && ! is_ANYOF_SYNTHETIC(and_with))
     {
         unsigned int i;
@@ -1797,7 +1807,7 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
 
         /* If either P1 or P2 is empty, the intersection will be also; can skip
          * the loop */
-        if (! (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL)) {
+        if (! (and_with_flags & ANYOF_MATCHES_POSIXL)) {
             ANYOF_POSIXL_ZERO(ssc);
         }
         else if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
@@ -1857,16 +1867,16 @@ S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
             else {
                 ssc->invlist = anded_cp_list;
                 ANYOF_POSIXL_ZERO(ssc);
-                if (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL) {
+                if (and_with_flags & ANYOF_MATCHES_POSIXL) {
                     ANYOF_POSIXL_OR((regnode_charclass_posixl*) and_with, ssc);
                 }
             }
         }
         else if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)
-                 || (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL))
+                 || (and_with_flags & ANYOF_MATCHES_POSIXL))
         {
             /* One or the other of P1, P2 is non-empty. */
-            if (ANYOF_FLAGS(and_with) & ANYOF_MATCHES_POSIXL) {
+            if (and_with_flags & ANYOF_MATCHES_POSIXL) {
                 ANYOF_POSIXL_AND((regnode_charclass_posixl*) and_with, ssc);
             }
             ssc_union(ssc, anded_cp_list, FALSE);
@@ -1887,6 +1897,7 @@ S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
 
     SV* ored_cp_list;
     U8 ored_flags;
+    U8  or_with_flags = (OP(or_with) == ANYOFH) ? 0 : ANYOF_FLAGS(or_with);
 
     PERL_ARGS_ASSERT_SSC_OR;
 
@@ -1896,17 +1907,17 @@ S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * the code point inversion list and just the relevant flags */
     if (is_ANYOF_SYNTHETIC(or_with)) {
         ored_cp_list = ((regnode_ssc*) or_with)->invlist;
-        ored_flags = ANYOF_FLAGS(or_with);
+        ored_flags = or_with_flags;
     }
     else {
         ored_cp_list = get_ANYOF_cp_list_for_ssc(pRExC_state, or_with);
-        ored_flags = ANYOF_FLAGS(or_with) & ANYOF_COMMON_FLAGS;
+        ored_flags = or_with_flags & ANYOF_COMMON_FLAGS;
         if (OP(or_with) != ANYOFD) {
             ored_flags
-            |= ANYOF_FLAGS(or_with)
+            |= or_with_flags
              & ( ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER
                 |ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP);
-            if (ANYOFL_UTF8_LOCALE_REQD(ANYOF_FLAGS(or_with))) {
+            if (ANYOFL_UTF8_LOCALE_REQD(or_with_flags)) {
                 ored_flags |=
                     ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
             }
@@ -1933,12 +1944,12 @@ S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
      * (which results in actually simpler code than the non-inverted case)
      * */
 
-    if ((ANYOF_FLAGS(or_with) & ANYOF_INVERT)
+    if ((or_with_flags & ANYOF_INVERT)
         && ! is_ANYOF_SYNTHETIC(or_with))
     {
         /* We ignore P2, leaving P1 going forward */
     }   /* else  Not inverted */
-    else if (ANYOF_FLAGS(or_with) & ANYOF_MATCHES_POSIXL) {
+    else if (or_with_flags & ANYOF_MATCHES_POSIXL) {
         ANYOF_POSIXL_OR((regnode_charclass_posixl*)or_with, ssc);
         if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
             unsigned int i;
@@ -2693,7 +2704,7 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
         trie_words = newAV();
     });
 
-    re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, 1);
+    re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, GV_ADD);
     assert(re_trie_maxbuff);
     if (!SvIOK(re_trie_maxbuff)) {
         sv_setiv(re_trie_maxbuff, RE_TRIE_MAXBUF_INIT);
@@ -4428,6 +4439,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                        /* recursed: which subroutines have we recursed into */
                        /* and_withp: Valid if flags & SCF_DO_STCLASS_OR */
 {
+    dVAR;
     /* There must be at least this number of characters to match */
     SSize_t min = 0;
     I32 pars = 0, code;
@@ -5609,9 +5621,12 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                        STRLEN l;
                        const char * const s = SvPV_const(data->last_found, l);
                        SSize_t old = b - data->last_start_min;
+                        assert(old >= 0);
 
                        if (UTF)
-                           old = utf8_hop((U8*)s, old) - (U8*)s;
+                           old = utf8_hop_forward((U8*)s, old,
+                                               (U8 *) SvEND(data->last_found))
+                                - (U8*)s;
                        l -= old;
                        /* Get the added string: */
                        last_str = newSVpvn_utf8(s  + old, l, UTF);
@@ -5976,14 +5991,27 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                                       last, &data_fake, stopparen,
                                       recursed_depth, NULL, f, depth+1);
                 if (scan->flags) {
-                    if (deltanext) {
-                       FAIL("Variable length lookbehind not implemented");
-                    }
-                    else if (minnext > (I32)U8_MAX) {
+                    if (   deltanext < 0
+                        || deltanext > (I32) U8_MAX
+                        || minnext > (I32)U8_MAX
+                        || minnext + deltanext > (I32)U8_MAX)
+                    {
                        FAIL2("Lookbehind longer than %" UVuf " not implemented",
                               (UV)U8_MAX);
                     }
-                    scan->flags = (U8)minnext;
+
+                    /* The 'next_off' field has been repurposed to count the
+                     * additional starting positions to try beyond the initial
+                     * one.  (This leaves it at 0 for non-variable length
+                     * matches to avoid breakage for those not using this
+                     * extension) */
+                    if (deltanext) {
+                        scan->next_off = deltanext;
+                        ckWARNexperimental(RExC_parse,
+                            WARN_EXPERIMENTAL__VLB,
+                            "Variable length lookbehind is experimental");
+                    }
+                    scan->flags = (U8)minnext + deltanext;
                 }
                 if (data) {
                     if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
@@ -6068,14 +6096,21 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                                         stopparen, recursed_depth, NULL,
                                         f, depth+1);
                 if (scan->flags) {
-                    if (deltanext) {
-                       FAIL("Variable length lookbehind not implemented");
-                    }
-                    else if (*minnextp > (I32)U8_MAX) {
+                    assert(0);  /* This code has never been tested since this
+                                   is normally not compiled */
+                    if (   deltanext < 0
+                        || deltanext > (I32) U8_MAX
+                        || *minnextp > (I32)U8_MAX
+                        || *minnextp + deltanext > (I32)U8_MAX)
+                    {
                        FAIL2("Lookbehind longer than %" UVuf " not implemented",
                               (UV)U8_MAX);
                     }
-                    scan->flags = (U8)*minnextp;
+
+                    if (deltanext) {
+                        scan->next_off = deltanext;
+                    }
+                    scan->flags = (U8)*minnextp + deltanext;
                 }
 
                 *minnextp += min;
@@ -7301,6 +7336,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
                    OP *expr, const regexp_engine* eng, REGEXP *old_re,
                     bool *is_bare_re, const U32 orig_rx_flags, const U32 pm_flags)
 {
+    dVAR;
     REGEXP *Rx;         /* Capital 'R' means points to a REGEXP */
     STRLEN plen;
     char *exp;
@@ -7358,6 +7394,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     }
 
     pRExC_state->warn_text = NULL;
+    pRExC_state->unlexed_names = NULL;
     pRExC_state->code_blocks = NULL;
 
     if (is_bare_re)
@@ -7656,6 +7693,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 
     RExC_naughty = 0;
     RExC_npar = 1;
+    RExC_parens_buf_size = 0;
     RExC_emit_start = RExC_rxi->program;
     pRExC_state->code_index = 0;
 
@@ -7665,9 +7703,9 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     /* Do the parse */
     if (reg(pRExC_state, 0, &flags, 1)) {
 
-        /* Success!, But if RExC_total_parens < 0, we need to redo the parse
-         * knowing how many parens there actually are */
-        if (RExC_total_parens < 0) {
+        /* Success!, But we may need to redo the parse knowing how many parens
+         * there actually are */
+        if (IN_PARENS_PASS) {
             flags |= RESTART_PARSE;
         }
 
@@ -7709,7 +7747,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
             DEBUG_PARSE_r(Perl_re_printf( aTHX_ "Need to redo parse\n"));
         }
 
-        if (RExC_total_parens > 0) {
+        if (ALL_PARENS_COUNTED) {
             /* Make enough room for all the known parens, and zero it */
             Renew(RExC_open_parens, RExC_total_parens, regnode_offset);
             Zero(RExC_open_parens, RExC_total_parens, regnode_offset);
@@ -8807,7 +8845,7 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
             /* It might be a forward reference; we can't fail until we
                 * know, by completing the parse to get all the groups, and
                 * then reparsing */
-            if (RExC_total_parens > 0)  {
+            if (ALL_PARENS_COUNTED)  {
                 vFAIL("Reference to nonexistent named group");
             }
             else {
@@ -10528,6 +10566,7 @@ Perl__invlistEQ(pTHX_ SV* const a, SV* const b, const bool complement_b)
 STATIC SV*
 S__make_exactf_invlist(pTHX_ RExC_state_t *pRExC_state, regnode *node)
 {
+    dVAR;
     const U8 * s = (U8*)STRING(node);
     SSize_t bytelen = STR_LEN(node);
     UV uc;
@@ -10895,7 +10934,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                 return;
             default:
               fail_modifiers:
-                RExC_parse += SKIP_IF_CHAR(RExC_parse);
+                RExC_parse += SKIP_IF_CHAR(RExC_parse, RExC_end);
                /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
                 vFAIL2utf8f("Sequence (%" UTF8f "...) not recognized",
                       UTF8fARG(UTF, RExC_parse-seqstart, seqstart));
@@ -10998,6 +11037,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
     I32 freeze_paren = 0;
     I32 after_freeze = 0;
     I32 num; /* numeric backreferences */
+    SV * max_open;  /* Max number of unclosed parens */
 
     char * parse_start = RExC_parse; /* MJD */
     char * const oregcomp_parse = RExC_parse;
@@ -11007,6 +11047,17 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
     PERL_ARGS_ASSERT_REG;
     DEBUG_PARSE("reg ");
 
+
+    max_open = get_sv(RE_COMPILE_RECURSION_LIMIT, GV_ADD);
+    assert(max_open);
+    if (!SvIOK(max_open)) {
+        sv_setiv(max_open, RE_COMPILE_RECURSION_INIT);
+    }
+    if (depth > 4 * SvIV(max_open)) { /* We increase depth by 4 for each open
+                                         paren */
+        vFAIL("Too many nested open parens");
+    }
+
     *flagp = 0;                                /* Tentatively. */
 
     /* Having this true makes it feasible to have a lot fewer tests for the
@@ -11295,7 +11346,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
 
            } /* End of switch */
            if ( ! op ) {
-               RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+               RExC_parse += UTF
+                              ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                              : 1;
                 if (has_upper || verb_len == 0) {
                     vFAIL2utf8f(
                     "Unknown verb pattern '%" UTF8f "'",
@@ -11375,7 +11428,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                     return handle_named_backref(pRExC_state, flagp,
                                                 parse_start, ')');
                 }
-                RExC_parse += SKIP_IF_CHAR(RExC_parse);
+                RExC_parse += SKIP_IF_CHAR(RExC_parse, RExC_end);
                 /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
                vFAIL3("Sequence (%.*s...) not recognized",
                                 RExC_parse-seqstart, seqstart);
@@ -11592,7 +11645,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                         /* It might be a forward reference; we can't fail until
                          * we know, by completing the parse to get all the
                          * groups, and then reparsing */
-                        if (RExC_total_parens > 0)  {
+                        if (ALL_PARENS_COUNTED)  {
                             RExC_parse++;
                             vFAIL("Reference to nonexistent group");
                         }
@@ -11618,7 +11671,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                     /* It might be a forward reference; we can't fail until we
                      * know, by completing the parse to get all the groups, and
                      * then reparsing */
-                    if (RExC_total_parens > 0)  {
+                    if (ALL_PARENS_COUNTED)  {
                         if (num >= RExC_total_parens) {
                             RExC_parse++;
                             vFAIL("Reference to nonexistent group");
@@ -11650,7 +11703,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
            case '?':           /* (??...) */
                is_logical = 1;
                if (*RExC_parse != '{') {
-                    RExC_parse += SKIP_IF_CHAR(RExC_parse);
+                    RExC_parse += SKIP_IF_CHAR(RExC_parse, RExC_end);
                     /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
                     vFAIL2utf8f(
                         "Sequence (%" UTF8f "...) not recognized",
@@ -11848,7 +11901,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
 
                  insert_if_check_paren:
                    if (UCHARAT(RExC_parse) != ')') {
-                        RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                        RExC_parse += UTF
+                                      ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                      : 1;
                        vFAIL("Switch condition not recognized");
                    }
                    nextchar(pRExC_state);
@@ -11910,7 +11965,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
 #endif
                    return ret;
                }
-                RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                RExC_parse += UTF
+                              ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                              : 1;
                 vFAIL("Unknown switch condition (?(...))");
            }
            case '[':           /* (?[ ... ]) */
@@ -11920,6 +11977,12 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                RExC_parse--; /* for vFAIL to print correctly */
                 vFAIL("Sequence (? incomplete");
                 break;
+
+            case ')':
+                if (RExC_strict) {  /* [perl #132851] */
+                    ckWARNreg(RExC_parse, "Empty (?) without any modifiers");
+                }
+                /* FALLTHROUGH */
            default: /* e.g., (?i) */
                RExC_parse = (char *) seqstart + 1;
               parse_flags:
@@ -11949,34 +12012,47 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
          capturing_parens:
            parno = RExC_npar;
            RExC_npar++;
-            if (RExC_total_parens <= 0) {
+            if (! ALL_PARENS_COUNTED) {
                 /* If we are in our first pass through (and maybe only pass),
                  * we  need to allocate memory for the capturing parentheses
-                 * data structures.  Since we start at npar=1, when it reaches
-                 * 2, for the first time it has something to put in it.  Above
-                 * 2 means we extend what we already have */
-                if (RExC_npar == 2) {
+                 * data structures.
+                 */
+
+                if (!RExC_parens_buf_size) {
+                    /* first guess at number of parens we might encounter */
+                    RExC_parens_buf_size = 10;
+
                     /* setup RExC_open_parens, which holds the address of each
                      * OPEN tag, and to make things simpler for the 0 index the
                      * start of the program - this is used later for offsets */
-                    Newxz(RExC_open_parens, RExC_npar, regnode_offset);
+                    Newxz(RExC_open_parens, RExC_parens_buf_size,
+                            regnode_offset);
                     RExC_open_parens[0] = 1;    /* +1 for REG_MAGIC */
 
                     /* setup RExC_close_parens, which holds the address of each
                      * CLOSE tag, and to make things simpler for the 0 index
                      * the end of the program - this is used later for offsets
                      * */
-                    Newxz(RExC_close_parens, RExC_npar, regnode_offset);
+                    Newxz(RExC_close_parens, RExC_parens_buf_size,
+                            regnode_offset);
                     /* we dont know where end op starts yet, so we dont need to
                      * set RExC_close_parens[0] like we do RExC_open_parens[0]
                      * above */
                 }
-                else {
-                    Renew(RExC_open_parens, RExC_npar, regnode_offset);
-                    Zero(RExC_open_parens + RExC_npar - 1, 1, regnode_offset);
+                else if (RExC_npar > RExC_parens_buf_size) {
+                    I32 old_size = RExC_parens_buf_size;
+
+                    RExC_parens_buf_size *= 2;
+
+                    Renew(RExC_open_parens, RExC_parens_buf_size,
+                            regnode_offset);
+                    Zero(RExC_open_parens + old_size,
+                            RExC_parens_buf_size - old_size, regnode_offset);
 
-                    Renew(RExC_close_parens, RExC_npar, regnode_offset);
-                    Zero(RExC_close_parens + RExC_npar - 1, 1, regnode_offset);
+                    Renew(RExC_close_parens, RExC_parens_buf_size,
+                            regnode_offset);
+                    Zero(RExC_close_parens + old_size,
+                            RExC_parens_buf_size - old_size, regnode_offset);
                 }
             }
 
@@ -12058,7 +12134,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
             RETURN_FAIL_ON_RESTART(flags, flagp);
             FAIL2("panic: regbranch returned failure, flags=%#" UVxf, (UV) flags);
         }
-        REGTAIL(pRExC_state, lastbr, br);               /* BRANCH -> BRANCH. */
+        if (!  REGTAIL(pRExC_state, lastbr, br)) {  /* BRANCH -> BRANCH. */
+            REQUIRE_BRANCHJ(flagp, 0);
+        }
        lastbr = br;
        *flagp |= flags & (SPSTART | HASWIDTH | POSTPONED);
     }
@@ -12129,7 +12207,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
                           (IV)(ender - lastbr)
             );
         );
-        REGTAIL(pRExC_state, lastbr, ender);
+        if (! REGTAIL(pRExC_state, lastbr, ender)) {
+            REQUIRE_BRANCHJ(flagp, 0);
+        }
 
        if (have_branch) {
             char is_nothing= 1;
@@ -12140,9 +12220,12 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
            for (br = REGNODE_p(ret); br; br = regnext(br)) {
                const U8 op = PL_regkind[OP(br)];
                if (op == BRANCH) {
-                    REGTAIL_STUDY(pRExC_state,
-                                  REGNODE_OFFSET(NEXTOPER(br)),
-                                  ender);
+                    if (! REGTAIL_STUDY(pRExC_state,
+                                        REGNODE_OFFSET(NEXTOPER(br)),
+                                        ender))
+                    {
+                        REQUIRE_BRANCHJ(flagp, 0);
+                    }
                     if ( OP(NEXTOPER(br)) != NOTHING
                          || regnext(NEXTOPER(br)) != REGNODE_p(ender))
                         is_nothing= 0;
@@ -12209,7 +12292,10 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
             Set_Node_Cur_Length(REGNODE_p(ret), parse_start);
            Set_Node_Offset(REGNODE_p(ret), parse_start + 1);
            FLAGS(REGNODE_p(ret)) = flag;
-            REGTAIL_STUDY(pRExC_state, ret, reg_node(pRExC_state, TAIL));
+            if (! REGTAIL_STUDY(pRExC_state, ret, reg_node(pRExC_state, TAIL)))
+            {
+                REQUIRE_BRANCHJ(flagp, 0);
+            }
        }
     }
 
@@ -12303,14 +12389,12 @@ S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
            /* FIXME adding one for every branch after the first is probably
             * excessive now we have TRIE support. (hv) */
            MARK_NAUGHTY(1);
-            if (     chain > (SSize_t) BRANCH_MAX_OFFSET
-                && ! RExC_use_BRANCHJ)
-            {
+            if (! REGTAIL(pRExC_state, chain, latest)) {
                 /* XXX We could just redo this branch, but figuring out what
-                 * bookkeeping needs to be reset is a pain */
+                 * bookkeeping needs to be reset is a pain, and it's likely
+                 * that other branches that goto END will also be too large */
                 REQUIRE_BRANCHJ(flagp, 0);
             }
-            REGTAIL(pRExC_state, chain, latest);
        }
        chain = latest;
        c++;
@@ -12610,20 +12694,23 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * points) that this \N sequence matches.  This is set, and the input is
   * parsed for errors, even if the function returns FALSE, as detailed below.
   *
-  * There are 5 possibilities here, as detailed in the next 5 paragraphs.
+  * There are 6 possibilities here, as detailed in the next 6 paragraphs.
   *
   * Probably the most common case is for the \N to specify a single code point.
   * *cp_count will be set to 1, and *code_point_p will be set to that code
   * point.
   *
-  * Another possibility is for the input to be an empty \N{}, which for
-  * backwards compatibility we accept.  *cp_count will be set to 0. *node_p
-  * will be set to a generated NOTHING node.
+  * Another possibility is for the input to be an empty \N{}.  This is no
+  * longer accepted, and will generate a fatal error.
+  *
+  * Another possibility is for a custom charnames handler to be in effect which
+  * translates the input name to an empty string.  *cp_count will be set to 0.
+  * *node_p will be set to a generated NOTHING node.
   *
   * Still another possibility is for the \N to mean [^\n]. *cp_count will be
   * set to 0. *node_p will be set to a generated REG_ANY node.
   *
-  * The fourth possibility is that \N resolves to a sequence of more than one
+  * The fifth possibility is that \N resolves to a sequence of more than one
   * code points.  *cp_count will be set to the number of code points in the
   * sequence. *node_p will be set to a generated node returned by this
   * function calling S_reg().
@@ -12631,7 +12718,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * The final possibility is that it is premature to be calling this function;
   * the parse needs to be restarted.  This can happen when this changes from
   * /d to /u rules, or when the pattern needs to be upgraded to UTF-8.  The
-  * latter occurs only when the fourth possibility would otherwise be in
+  * latter occurs only when the fifth possibility would otherwise be in
   * effect, and is because one of those code points requires the pattern to be
   * recompiled as UTF-8.  The function returns FALSE, and sets the
   * RESTART_PARSE and NEED_UTF8 flags in *flagp, as appropriate.  When this
@@ -12648,12 +12735,11 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * so we need a way to take a snapshot of what they resolve to at the time of
   * the original parse. [perl #56444].
   *
-  * That parsing is skipped for single-quoted regexes, so we may here get
-  * '\N{NAME}'.  This is a fatal error.  These names have to be resolved by the
-  * parser.  But if the single-quoted regex is something like '\N{U+41}', that
-  * is legal and handled here.  The code point is Unicode, and has to be
-  * translated into the native character set for non-ASCII platforms.
-  */
+  * That parsing is skipped for single-quoted regexes, so here we may get
+  * '\N{NAME}', which is parsed now.  If the single-quoted regex is something
+  * like '\N{U+41}', that code point is Unicode, and has to be translated into
+  * the native character set for non-ASCII platforms.  The other possibilities
+  * are already native, so no translation is done. */
 
     char * endbrace;    /* points to '}' following the name */
     char* p = RExC_parse; /* Temporary */
@@ -12662,7 +12748,6 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
     char *orig_end;
     char *save_start;
     I32 flags;
-    Size_t count = 0;   /* code point count kept internally by this function */
 
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -12685,7 +12770,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
 
     /* Disambiguate between \N meaning a named character versus \N meaning
      * [^\n].  The latter is assumed when the {...} following the \N is a legal
-     * quantifier, or there is no '{' at all */
+     * quantifier, or if there is no '{' at all */
     if (*p != '{' || regcurly(p)) {
         RExC_parse = p;
         if (cp_count) {
@@ -12718,15 +12803,19 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         vFAIL2("Missing right brace on \\%c{}", 'N');
     }
 
-    /* Here, we have decided it should be a named character or sequence */
-    REQUIRE_UNI_RULES(flagp, FALSE); /* Unicode named chars imply Unicode
-                                        semantics */
+    /* Here, we have decided it should be a named character or sequence.  These
+     * imply Unicode semantics */
+    REQUIRE_UNI_RULES(flagp, FALSE);
 
-    if (endbrace == RExC_parse) {   /* empty: \N{} */
+    /* \N{_} is what toke.c returns to us to indicate a name that evaluates to
+     * nothing at all (not allowed under strict) */
+    if (endbrace - RExC_parse == 1 && *RExC_parse == '_') {
+        RExC_parse = endbrace;
         if (strict) {
             RExC_parse++;   /* Position after the "}" */
             vFAIL("Zero length \\N{}");
         }
+
         if (cp_count) {
             *cp_count = 0;
         }
@@ -12739,15 +12828,122 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         return TRUE;
     }
 
-    /* If we haven't got something that begins with 'U+', then it didn't get lexed. */
-    if (   endbrace - RExC_parse < 2
-        || strnNE(RExC_parse, "U+", 2))
-    {
-        RExC_parse = endbrace;  /* position msg's '<--HERE' */
-        vFAIL("\\N{NAME} must be resolved by the lexer");
-    }
+    if (endbrace - RExC_parse < 2 || ! strBEGINs(RExC_parse, "U+")) {
+
+        /* Here, the name isn't of the form  U+....  This can happen if the
+         * pattern is single-quoted, so didn't get evaluated in toke.c.  Now
+         * is the time to find out what the name means */
+
+        const STRLEN name_len = endbrace - RExC_parse;
+        SV *  value_sv;     /* What does this name evaluate to */
+        SV ** value_svp;
+        const U8 * value;   /* string of name's value */
+        STRLEN value_len;   /* and its length */
+
+        /*  RExC_unlexed_names is a hash of names that weren't evaluated by
+         *  toke.c, and their values. Make sure is initialized */
+        if (! RExC_unlexed_names) {
+            RExC_unlexed_names = newHV();
+        }
+
+        /* If we have already seen this name in this pattern, use that.  This
+         * allows us to only call the charnames handler once per name per
+         * pattern.  A broken or malicious handler could return something
+         * different each time, which could cause the results to vary depending
+         * on if something gets added or subtracted from the pattern that
+         * causes the number of passes to change, for example */
+        if ((value_svp = hv_fetch(RExC_unlexed_names, RExC_parse,
+                                                      name_len, 0)))
+        {
+            value_sv = *value_svp;
+        }
+        else { /* Otherwise we have to go out and get the name */
+            const char * error_msg = NULL;
+            value_sv = get_and_check_backslash_N_name(RExC_parse, endbrace,
+                                                      UTF,
+                                                      &error_msg);
+            if (error_msg) {
+                RExC_parse = endbrace;
+                vFAIL(error_msg);
+            }
+
+            /* If no error message, should have gotten a valid return */
+            assert (value_sv);
+
+            /* Save the name's meaning for later use */
+            if (! hv_store(RExC_unlexed_names, RExC_parse, name_len,
+                           value_sv, 0))
+            {
+                Perl_croak(aTHX_ "panic: hv_store() unexpectedly failed");
+            }
+        }
+
+        /* Here, we have the value the name evaluates to in 'value_sv' */
+        value = (U8 *) SvPV(value_sv, value_len);
+
+        /* See if the result is one code point vs 0 or multiple */
+        if (value_len > 0 && value_len <= ((SvUTF8(value_sv))
+                                           ? UTF8SKIP(value)
+                                           : 1))
+        {
+            /* Here, exactly one code point.  If that isn't what is wanted,
+             * fail */
+            if (! code_point_p) {
+                RExC_parse = p;
+                return FALSE;
+            }
+
+            /* Convert from string to numeric code point */
+            *code_point_p = (SvUTF8(value_sv))
+                            ? valid_utf8_to_uvchr(value, NULL)
+                            : *value;
+
+            /* Have parsed this entire single code point \N{...}.  *cp_count
+             * has already been set to 1, so don't do it again. */
+            RExC_parse = endbrace;
+            nextchar(pRExC_state);
+            return TRUE;
+        } /* End of is a single code point */
+
+        /* Count the code points, if caller desires.  The API says to do this
+         * even if we will later return FALSE */
+        if (cp_count) {
+            *cp_count = 0;
+
+            *cp_count = (SvUTF8(value_sv))
+                        ? utf8_length(value, value + value_len)
+                        : value_len;
+        }
+
+        /* Fail if caller doesn't want to handle a multi-code-point sequence.
+         * But don't back the pointer up if the caller wants to know how many
+         * code points there are (they need to handle it themselves in this
+         * case).  */
+        if (! node_p) {
+            if (! cp_count) {
+                RExC_parse = p;
+            }
+            return FALSE;
+        }
+
+        /* Convert this to a sub-pattern of the form "(?: ... )", and then call
+         * reg recursively to parse it.  That way, it retains its atomicness,
+         * while not having to worry about any special handling that some code
+         * points may have. */
+
+        substitute_parse = newSVpvs("?:");
+        sv_catsv(substitute_parse, value_sv);
+        sv_catpv(substitute_parse, ")");
+
+#ifdef EBCDIC
+        /* The value should already be native, so no need to convert on EBCDIC
+         * platforms.*/
+        assert(! RExC_recode_x_to_native);
+#endif
 
-        /* This code purposely indented below because of future changes coming */
+    }
+    else {   /* \N{U+...} */
+        Size_t count = 0;   /* code point count kept internally */
 
         /* We can get to here when the input is \N{U+...} or when toke.c has
          * converted a name to the \N{U+...} form.  This include changing a
@@ -12882,6 +13078,8 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         RExC_recode_x_to_native = 1;
 #endif
 
+    }
+
     /* Here, we have the string the name evaluates to, ready to be parsed,
      * stored in 'substitute_parse' as a series of valid "\x{...}\x{...}"
      * constructs.  This can be called from within a substitute parse already.
@@ -13078,6 +13276,7 @@ S_backref_value(char *p, char *e)
 STATIC regnode_offset
 S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 {
+    dVAR;
     regnode_offset ret = 0;
     I32 flags = 0;
     char *parse_start;
@@ -13268,9 +13467,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 char name = *RExC_parse;
                 char * endbrace = NULL;
                 RExC_parse += 2;
-                if (RExC_parse < RExC_end) {
-                    endbrace = (char *) memchr(RExC_parse, '}', RExC_end - RExC_parse);
-                }
+                endbrace = (char *) memchr(RExC_parse, '}', RExC_end - RExC_parse);
 
                 if (! endbrace) {
                     vFAIL2("Missing right brace on \\%c{}", name);
@@ -13615,7 +13812,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                     /* It might be a forward reference; we can't fail until we
                      * know, by completing the parse to get all the groups, and
                      * then reparsing */
-                    if (RExC_total_parens > 0)  {
+                    if (ALL_PARENS_COUNTED)  {
                         if (num >= RExC_total_parens)  {
                             vFAIL("Reference to nonexistent group");
                         }
@@ -13767,7 +13964,6 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                    || UTF8_IS_INVARIANT(UCHARAT(RExC_parse))
                    || UTF8_IS_START(UCHARAT(RExC_parse)));
 
-
             /* Here, we have a literal character.  Find the maximal string of
              * them in the input that we can fit into a single EXACTish node.
              * We quit at the first non-literal or when the node gets full, or
@@ -14343,7 +14539,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 else {
 
                     /* Point to the first byte of the final character */
-                    s = (char *) utf8_hop((U8 *) s, -1);
+                    s = (char *) utf8_hop_back((U8 *) s, -1, (U8 *) s0);
 
                     while (s >= s0) {   /* Search backwards until find
                                            a non-problematic char */
@@ -14576,6 +14772,8 @@ S_populate_ANYOF_from_invlist(pTHX_ regnode *node, SV** invlist_ptr)
      * sets up the bitmap and any flags, removing those code points from the
      * inversion list, setting it to NULL should it become completely empty */
 
+    dVAR;
+
     PERL_ARGS_ASSERT_POPULATE_ANYOF_FROM_INVLIST;
     assert(PL_regkind[OP(node)] == ANYOF);
 
@@ -15689,7 +15887,9 @@ redo_curchar:
                             RExC_parse = RExC_end;
                         }
                         else if (RExC_parse != save_parse) {
-                            RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                            RExC_parse += (UTF)
+                                          ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                          : 1;
                         }
                         vFAIL("Expecting '(?flags:(?[...'");
                     }
@@ -16471,10 +16671,11 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * UTF-8
      */
 
+    dVAR;
     UV prevvalue = OOB_UNICODE, save_prevvalue = OOB_UNICODE;
     IV range = 0;
     UV value = OOB_UNICODE, save_value = OOB_UNICODE;
-    regnode_offset ret;
+    regnode_offset ret = -1;    /* Initialized to an illegal value */
     STRLEN numlen;
     int namedclass = OOB_NAMEDCLASS;
     char *rangebegin = NULL;
@@ -16792,6 +16993,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                               "Ignoring zero length \\N{} in character class");
                         }
                         else { /* cp_count > 1 */
+                            assert(cp_count > 1);
                             if (! RExC_in_multi_char_class) {
                                 if (invert || range || *RExC_parse == '-') {
                                     if (strict) {
@@ -16874,7 +17076,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                }   /* The \p isn't immediately followed by a '{' */
                else if (! isALPHA(*RExC_parse)) {
-                    RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                    RExC_parse += (UTF)
+                                  ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                  : 1;
                     vFAIL2("Character following \\%c must be '{' or a "
                            "single-character Unicode property name",
                            (U8) value);
@@ -16896,6 +17100,12 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                     SV * prop_definition = parse_uniprop_string(
                                             name, n, UTF, FOLD,
                                             FALSE, /* This is compile-time */
+
+                                            /* We can't defer this defn when
+                                             * the full result is required in
+                                             * this call */
+                                            ! cBOOL(ret_invlist),
+
                                             &user_defined,
                                             msg,
                                             0 /* Base level */
@@ -17043,7 +17253,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                    RExC_parse += numlen;
                     if (numlen != 3) {
                         if (strict) {
-                            RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                            RExC_parse += (UTF)
+                                          ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                                          : 1;
                             vFAIL("Need exactly 3 octal digits");
                         }
                         else if (   numlen < 3 /* like \08, \178 */
@@ -18057,9 +18269,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
             invlist_iterinit(cp_list);
             for (i = 0; i <= MAX_FOLD_FROMS; i++) {
-                if (invlist_iternext(cp_list, &start[i], &end[i])) {
-                    partial_cp_count += end[i] - start[i] + 1;
+                if (invlist_iternext(cp_list, &start[i], &end[i])) {
+                    break;
                 }
+                partial_cp_count += end[i] - start[i] + 1;
             }
 
             invlist_iterfinish(cp_list);
@@ -18410,10 +18623,12 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                      * inversion list, making sure everything is included. */
                     fold_list = add_cp_to_invlist(fold_list, start[0]);
                     fold_list = add_cp_to_invlist(fold_list, folded);
-                    fold_list = add_cp_to_invlist(fold_list, first_fold);
-                    for (i = 0; i < folds_to_this_cp_count - 1; i++) {
-                        fold_list = add_cp_to_invlist(fold_list,
+                    if (folds_to_this_cp_count > 0) {
+                        fold_list = add_cp_to_invlist(fold_list, first_fold);
+                        for (i = 0; i + 1 < folds_to_this_cp_count; i++) {
+                            fold_list = add_cp_to_invlist(fold_list,
                                                         remaining_folds[i]);
+                        }
                     }
 
                     /* If the fold list is identical to what's in this ANYOF
@@ -18771,8 +18986,34 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         * bitmap, optimize to indicate that */
         if (     start[0] >= NUM_ANYOF_CODE_POINTS
             && ! LOC
-            && ! upper_latin1_only_utf8_matches)
+            && ! upper_latin1_only_utf8_matches
+            &&   anyof_flags == 0)
         {
+            UV highest_cp = invlist_highest(cp_list);
+
+            /* If the lowest and highest code point in the class have the same
+             * UTF-8 first byte, then all do, and we can store that byte for
+             * regexec.c to use so that it can more quickly scan the target
+             * string for potential matches for this class.  We co-opt the the
+             * flags field for this.  Zero means, they don't have the same
+             * first byte.  We do accept here very large code points (for
+             * future use), but don't bother with this optimization for them,
+             * as it would cause other complications */
+            if (highest_cp > IV_MAX) {
+                anyof_flags = 0;
+            }
+            else {
+                U8 low_utf8[UTF8_MAXBYTES+1];
+                U8 high_utf8[UTF8_MAXBYTES+1];
+
+                (void) uvchr_to_utf8(low_utf8, start[0]);
+                (void) uvchr_to_utf8(high_utf8, invlist_highest(cp_list));
+
+                anyof_flags = (low_utf8[0] == high_utf8[0])
+                            ? low_utf8[0]
+                            : 0;
+            }
+
             op = ANYOFH;
         }
     }   /* End of seeing if can optimize it into a different node */
@@ -18973,6 +19214,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
                                                            stored here for just
                                                            this occasion */
                             TRUE,           /* run time */
+                            FALSE,          /* This call must find the defn */
                             si,             /* The property definition  */
                             &user_defined,
                             msg,
@@ -19249,7 +19491,9 @@ S_nextchar(pTHX_ RExC_state_t *pRExC_state)
                || UTF8_IS_INVARIANT(*RExC_parse)
                || UTF8_IS_START(*RExC_parse));
 
-        RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+        RExC_parse += (UTF)
+                      ? UTF8_SAFE_SKIP(RExC_parse, RExC_end)
+                      : 1;
 
         skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                                 FALSE /* Don't force /x */ );
@@ -19419,7 +19663,11 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, const U8 op,
     src = REGNODE_p(RExC_emit);
     RExC_emit += size;
     dst = REGNODE_p(RExC_emit);
-    if (RExC_open_parens) {
+
+    /* If we are in a "count the parentheses" pass, the numbers are unreliable,
+     * and [perl #133871] shows this can lead to problems, so skip this
+     * realignment of parens until a later pass when they are reliable */
+    if (! IN_PARENS_PASS && RExC_open_parens) {
         int paren;
         /*DEBUG_PARSE_FMT("inst"," - %" IVdf, (IV)RExC_npar);*/
         /* remember that RExC_npar is rex->nparens + 1,
@@ -19492,10 +19740,13 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, const U8 op,
 }
 
 /*
-- regtail - set the next-pointer at the end of a node chain of p to val.
+- regtail - set the next-pointer at the end of a node chain of p to val.  If
+            that value won't fit in the space available, instead returns FALSE.
+            (Except asserts if we can't fit in the largest space the regex
+            engine is designed for.)
 - SEE ALSO: regtail_study
 */
-STATIC void
+STATIC bool
 S_regtail(pTHX_ RExC_state_t * pRExC_state,
                 const regnode_offset p,
                 const regnode_offset val,
@@ -19528,11 +19779,21 @@ S_regtail(pTHX_ RExC_state_t * pRExC_state,
     }
 
     if (reg_off_by_arg[OP(REGNODE_p(scan))]) {
+        assert(val - scan <= U32_MAX);
         ARG_SET(REGNODE_p(scan), val - scan);
     }
     else {
+        if (val - scan > U16_MAX) {
+            /* Since not all callers check the return value, populate this with
+             * something that won't loop and will likely lead to a crash if
+             * execution continues */
+            NEXT_OFF(REGNODE_p(scan)) = U16_MAX;
+            return FALSE;
+        }
         NEXT_OFF(REGNODE_p(scan)) = val - scan;
     }
+
+    return TRUE;
 }
 
 #ifdef DEBUGGING
@@ -19549,10 +19810,14 @@ that it is purely analytical.
 Currently only used when in DEBUG mode. The macro REGTAIL_STUDY() is used
 to control which is which.
 
+This used to return a value that was ignored.  It was a problem that it is
+#ifdef'd to be another function that didn't return a value.  khw has changed it
+so both currently return a pass/fail return.
+
 */
 /* TODO: All four parms should be const */
 
-STATIC U8
+STATIC bool
 S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
                       const regnode_offset val, U32 depth)
 {
@@ -19576,7 +19841,7 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
            bool unfolded_multi_char;   /* Unexamined in this routine */
             if (join_exact(pRExC_state, scan, &min,
                            &unfolded_multi_char, 1, REGNODE_p(val), depth+1))
-                return EXACT;
+                return TRUE; /* Was return EXACT */
        }
 #endif
         if ( exact ) {
@@ -19626,13 +19891,18 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
         );
     });
     if (reg_off_by_arg[OP(REGNODE_p(scan))]) {
+        assert(val - scan <= U32_MAX);
        ARG_SET(REGNODE_p(scan), val - scan);
     }
     else {
+        if (val - scan > U16_MAX) {
+            NEXT_OFF(REGNODE_p(scan)) = U16_MAX;
+            return FALSE;
+        }
        NEXT_OFF(REGNODE_p(scan)) = val - scan;
     }
 
-    return exact;
+    return TRUE; /* Was 'return exact' */
 }
 #endif
 
@@ -19894,6 +20164,7 @@ void
 Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_info *reginfo, const RExC_state_t *pRExC_state)
 {
 #ifdef DEBUGGING
+    dVAR;
     int k;
     RXi_GET_DECL(prog, progi);
     GET_RE_DEBUG_FLAGS_DECL;
@@ -20043,7 +20314,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         /* 2: embedded, otherwise 1 */
        Perl_sv_catpvf(aTHX_ sv, "[%d]", o->flags);
     else if (k == ANYOF) {
-       const U8 flags = ANYOF_FLAGS(o);
+       const U8 flags = (OP(o) == ANYOFH) ? 0 : ANYOF_FLAGS(o);
         bool do_sep = FALSE;    /* Do we need to separate various components of
                                    the output? */
         /* Set if there is still an unresolved user-defined property */
@@ -20197,6 +20468,11 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         /* And finally the matching, closing ']' */
        Perl_sv_catpvf(aTHX_ sv, "%s]", PL_colors[1]);
 
+        if (OP(o) == ANYOFH && FLAGS(o) != 0) {
+            Perl_sv_catpvf(aTHX_ sv, " (First UTF-8 byte=\\x%02x)", FLAGS(o));
+        }
+
+
         SvREFCNT_dec(unresolved);
     }
     else if (k == ANYOFM) {
@@ -20239,8 +20515,13 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         assert(FLAGS(o) < C_ARRAY_LENGTH(bounds));
         sv_catpv(sv, bounds[FLAGS(o)]);
     }
-    else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH))
-       Perl_sv_catpvf(aTHX_ sv, "[%d]", -(o->flags));
+    else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH)) {
+       Perl_sv_catpvf(aTHX_ sv, "[%d", -(o->flags));
+        if (o->next_off) {
+            Perl_sv_catpvf(aTHX_ sv, "..-%d", o->flags - o->next_off);
+        }
+       Perl_sv_catpvf(aTHX_ sv, "]");
+    }
     else if (OP(o) == SBOL)
         Perl_sv_catpvf(aTHX_ sv, " /%s/", o->flags ? "\\A" : "^");
 
@@ -21186,6 +21467,7 @@ S_put_charclass_bitmap_innards_common(pTHX_
      * output would have been only the inversion indicator '^', NULL is instead
      * returned. */
 
+    dVAR;
     SV * output;
 
     PERL_ARGS_ASSERT_PUT_CHARCLASS_BITMAP_INNARDS_COMMON;
@@ -21289,6 +21571,8 @@ S_put_charclass_bitmap_innards(pTHX_ SV *sv,
      * whether the class itself is to be inverted.  However,  there are some
      * cases where it can't try inverting, as what actually matches isn't known
      * until runtime, and hence the inversion isn't either. */
+
+    dVAR;
     bool inverting_allowed = ! force_as_is_display;
 
     int i;
@@ -21683,6 +21967,8 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
 void
 Perl_init_uniprops(pTHX)
 {
+    dVAR;
+
     PL_user_def_props = newHV();
 
 #ifdef USE_ITHREADS
@@ -21762,6 +22048,7 @@ Perl_init_uniprops(pTHX)
     PL_utf8_foldclosures = _new_invlist_C_array(_Perl_IVCF_invlist);
     PL_utf8_mark = _new_invlist_C_array(uni_prop_ptrs[UNI_M]);
     PL_CCC_non0_non230 = _new_invlist_C_array(_Perl_CCC_non0_non230_invlist);
+    PL_Private_Use = _new_invlist_C_array(uni_prop_ptrs[UNI_CO]);
 
 #ifdef UNI_XIDC
     /* The below are used only by deprecated functions.  They could be removed */
@@ -21829,6 +22116,8 @@ Perl_handle_user_defined_property(pTHX_
     const bool is_utf8,         /* ? Is 'name' encoded in UTF-8 */
     const bool to_fold,         /* ? Is this under /i */
     const bool runtime,         /* ? Are we in compile- or run-time */
+    const bool deferrable,      /* Is it ok for this property's full definition
+                                   to be deferred until later? */
     SV* contents,               /* The property's definition */
     bool *user_defined_ptr,     /* This will be set TRUE as we wouldn't be
                                    getting called unless this is thought to be
@@ -22016,6 +22305,7 @@ Perl_handle_user_defined_property(pTHX_
 
         this_definition = parse_uniprop_string(s0, s - s0,
                                                is_utf8, to_fold, runtime,
+                                               deferrable,
                                                user_defined_ptr, msg,
                                                (name_len == 0)
                                                 ? level /* Don't increase level
@@ -22117,6 +22407,7 @@ S_delete_recursion_entry(pTHX_ void *key)
      * properties.  This is a function so it can be set up to be called even if
      * the program unexpectedly quits */
 
+    dVAR;
     SV ** current_entry;
     const STRLEN key_len = strlen((const char *) key);
     DECLARATION_FOR_GLOBAL_CONTEXT;
@@ -22166,6 +22457,8 @@ Perl_parse_uniprop_string(pTHX_
     const bool is_utf8,         /* ? Is 'name' encoded in UTF-8 */
     const bool to_fold,         /* ? Is this under /i */
     const bool runtime,         /* TRUE if this is being called at run time */
+    const bool deferrable,      /* TRUE if it's ok for the definition to not be
+                                   known at this call */
     bool *user_defined_ptr,     /* Upon return from this function it will be
                                    set to TRUE if any component is a
                                    user-defined property */
@@ -22173,6 +22466,7 @@ Perl_parse_uniprop_string(pTHX_
                                    this */
    const STRLEN level)          /* Recursion level of this call */
 {
+    dVAR;
     char* lookup_name;          /* normalized name for lookup in our tables */
     unsigned lookup_len;        /* Its length */
     bool stricter = FALSE;      /* Some properties have stricter name
@@ -22312,6 +22606,168 @@ Perl_parse_uniprop_string(pTHX_
             }
         }
 
+        /* Most punctuation after the equals indicates a subpattern, like
+         * \p{foo=/bar/} */
+        if (   isPUNCT_A(name[i])
+            && name[i] != '-'
+            && name[i] != '+'
+            && name[i] != '_'
+            && name[i] != '{')
+        {
+            /* Find the property.  The table includes the equals sign, so we
+             * use 'j' as-is */
+            table_index = match_uniprop((U8 *) lookup_name, j);
+            if (table_index) {
+                const char * const * prop_values
+                                            = UNI_prop_value_ptrs[table_index];
+                SV * subpattern;
+                Size_t subpattern_len;
+                REGEXP * subpattern_re;
+                char open = name[i++];
+                char close;
+                const char * pos_in_brackets;
+                bool escaped = 0;
+
+                /* A backslash means the real delimitter is the next character.
+                 * */
+                if (open == '\\') {
+                    open = name[i++];
+                    escaped = 1;
+                }
+
+                /* This data structure is constructed so that the matching
+                 * closing bracket is 3 past its matching opening.  The second
+                 * set of closing is so that if the opening is something like
+                 * ']', the closing will be that as well.  Something similar is
+                 * done in toke.c */
+                pos_in_brackets = strchr("([<)]>)]>", open);
+                close = (pos_in_brackets) ? pos_in_brackets[3] : open;
+
+                if (   name[name_len-1] != close
+                    || (escaped && name[name_len-2] != '\\'))
+                {
+                    sv_catpvs(msg, "Unicode property wildcard not terminated");
+                    goto append_name_to_msg;
+                }
+
+                Perl_ck_warner_d(aTHX_
+                    packWARN(WARN_EXPERIMENTAL__UNIPROP_WILDCARDS),
+                    "The Unicode property wildcards feature is experimental");
+
+                /* Now create and compile the wildcard subpattern.  Use /iaa
+                 * because nothing outside of ASCII will match, and it the
+                 * property values should all match /i.  Note that when the
+                 * pattern fails to compile, our added text to the user's
+                 * pattern will be displayed to the user, which is not so
+                 * desirable. */
+                subpattern_len = name_len - i - 1 - escaped;
+                subpattern = Perl_newSVpvf(aTHX_ "(?iaa:%.*s)",
+                                              (unsigned) subpattern_len,
+                                              name + i);
+                subpattern = sv_2mortal(subpattern);
+                subpattern_re = re_compile(subpattern, 0);
+                assert(subpattern_re);  /* Should have died if didn't compile
+                                         successfully */
+
+                /* For each legal property value, see if the supplied pattern
+                 * matches it. */
+                while (*prop_values) {
+                    const char * const entry = *prop_values;
+                    const Size_t len = strlen(entry);
+                    SV* entry_sv = newSVpvn_flags(entry, len, SVs_TEMP);
+
+                    if (pregexec(subpattern_re,
+                                 (char *) entry,
+                                 (char *) entry + len,
+                                 (char *) entry, 0,
+                                 entry_sv,
+                                 0))
+                    { /* Here, matched.  Add to the returned list */
+                        Size_t total_len = j + len;
+                        SV * sub_invlist = NULL;
+                        char * this_string;
+
+                        /* We know this is a legal \p{property=value}.  Call
+                         * the function to return the list of code points that
+                         * match it */
+                        Newxz(this_string, total_len + 1, char);
+                        Copy(lookup_name, this_string, j, char);
+                        my_strlcat(this_string, entry, total_len + 1);
+                        SAVEFREEPV(this_string);
+                        sub_invlist = parse_uniprop_string(this_string,
+                                                           total_len,
+                                                           is_utf8,
+                                                           to_fold,
+                                                           runtime,
+                                                           deferrable,
+                                                           user_defined_ptr,
+                                                           msg,
+                                                           level + 1);
+                        _invlist_union(prop_definition, sub_invlist,
+                                       &prop_definition);
+                    }
+
+                    prop_values++;  /* Next iteration, look at next propvalue */
+                } /* End of looking through property values; (the data
+                     structure is terminated by a NULL ptr) */
+
+                SvREFCNT_dec_NN(subpattern_re);
+
+                if (prop_definition) {
+                    return prop_definition;
+                }
+
+                sv_catpvs(msg, "No Unicode property value wildcard matches:");
+                goto append_name_to_msg;
+            }
+
+            /* Here's how khw thinks we should proceed to handle the properties
+             * not yet done:    Bidi Mirroring Glyph
+                                Bidi Paired Bracket
+                                Case Folding  (both full and simple)
+                                Decomposition Mapping
+                                Equivalent Unified Ideograph
+                                Name
+                                Name Alias
+                                Lowercase Mapping  (both full and simple)
+                                NFKC Case Fold
+                                Titlecase Mapping  (both full and simple)
+                                Uppercase Mapping  (both full and simple)
+             * Move the part that looks at the property values into a perl
+             * script, like utf8_heavy.pl is done.  This makes things somewhat
+             * easier, but most importantly, it avoids always adding all these
+             * strings to the memory usage when the feature is little-used.
+             *
+             * The property values would all be concatenated into a single
+             * string per property with each value on a separate line, and the
+             * code point it's for on alternating lines.  Then we match the
+             * user's input pattern m//mg, without having to worry about their
+             * uses of '^' and '$'.  Only the values that aren't the default
+             * would be in the strings.  Code points would be in UTF-8.  The
+             * search pattern that we would construct would look like
+             * (?: \n (code-point_re) \n (?aam: user-re ) \n )
+             * And so $1 would contain the code point that matched the user-re.
+             * For properties where the default is the code point itself, such
+             * as any of the case changing mappings, the string would otherwise
+             * consist of all Unicode code points in UTF-8 strung together.
+             * This would be impractical.  So instead, examine their compiled
+             * pattern, looking at the ssc.  If none, reject the pattern as an
+             * error.  Otherwise run the pattern against every code point in
+             * the ssc.  The ssc is kind of like tr18's 3.9 Possible Match Sets
+             * And it might be good to create an API to return the ssc.
+             *
+             * For the name properties, a new function could be created in
+             * charnames which essentially does the same thing as above,
+             * sharing Name.pl with the other charname functions.  Don't know
+             * about loose name matching, or algorithmically determined names.
+             * Decomposition.pl similarly.
+             *
+             * It might be that a new pattern modifier would have to be
+             * created, like /t for resTricTed, which changed the behavior of
+             * some constructs in their subpattern, like \A. */
+        } /* End of is a wildcard subppattern */
+
+
         /* Certain properties whose values are numeric need special handling.
          * They may optionally be prefixed by 'is'.  Ignore that prefix for the
          * purposes of checking if this is one of those properties */
@@ -22732,6 +23188,7 @@ Perl_parse_uniprop_string(pTHX_
                  * handle it */
                 prop_definition = handle_user_defined_property(name, name_len,
                                                     is_utf8, to_fold, runtime,
+                                                    deferrable,
                                                     POPs, user_defined_ptr,
                                                     msg,
                                                     level);
@@ -22821,7 +23278,7 @@ Perl_parse_uniprop_string(pTHX_
                  * compile time, it might just be that the subroutine for that
                  * property hasn't been encountered yet, but at runtime, it's
                  * an error to try to use an undefined one */
-                if (runtime) {
+                if (! deferrable) {
                     if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
                     sv_catpvs(msg, "Unknown user-defined property name");
                     goto append_name_to_msg;
@@ -23021,10 +23478,66 @@ Perl_parse_uniprop_string(pTHX_
 
     /* Create and return the inversion list */
     prop_definition =_new_invlist_C_array(uni_prop_ptrs[table_index]);
+    sv_2mortal(prop_definition);
+
+
+    /* See if there is a private use override to add to this definition */
+    {
+        COPHH * hinthash = (IN_PERL_COMPILETIME)
+                           ? CopHINTHASH_get(&PL_compiling)
+                           : CopHINTHASH_get(PL_curcop);
+       SV * pu_overrides = cophh_fetch_pv(hinthash, "private_use", 0, 0);
+
+        if (UNLIKELY(pu_overrides && SvPOK(pu_overrides))) {
+
+            /* See if there is an element in the hints hash for this table */
+            SV * pu_lookup = Perl_newSVpvf(aTHX_ "%d=", table_index);
+            const char * pos = strstr(SvPVX(pu_overrides), SvPVX(pu_lookup));
+
+            if (pos) {
+                bool dummy;
+                SV * pu_definition;
+                SV * pu_invlist;
+                SV * expanded_prop_definition =
+                            sv_2mortal(invlist_clone(prop_definition, NULL));
+
+                /* If so, it's definition is the string from here to the next
+                 * \a character.  And its format is the same as a user-defined
+                 * property */
+                pos += SvCUR(pu_lookup);
+                pu_definition = newSVpvn(pos, strchr(pos, '\a') - pos);
+                pu_invlist = handle_user_defined_property(lookup_name,
+                                                          lookup_len,
+                                                          0, /* Not UTF-8 */
+                                                          0, /* Not folded */
+                                                          runtime,
+                                                          deferrable,
+                                                          pu_definition,
+                                                          &dummy,
+                                                          msg,
+                                                          level);
+                if (TAINT_get) {
+                    if (SvCUR(msg) > 0) sv_catpvs(msg, "; ");
+                    sv_catpvs(msg, "Insecure private-use override");
+                    goto append_name_to_msg;
+                }
+
+                /* For now, as a safety measure, make sure that it doesn't
+                 * override non-private use code points */
+                _invlist_intersection(pu_invlist, PL_Private_Use, &pu_invlist);
+
+                /* Add it to the list to be returned */
+                _invlist_union(prop_definition, pu_invlist,
+                               &expanded_prop_definition);
+                prop_definition = expanded_prop_definition;
+                Perl_ck_warner_d(aTHX_ packWARN(WARN_EXPERIMENTAL__PRIVATE_USE), "The private_use feature is experimental");
+            }
+        }
+    }
+
     if (invert_return) {
         _invlist_invert(prop_definition);
     }
-    sv_2mortal(prop_definition);
     return prop_definition;