X-Git-Url: http://git.vpit.fr/?p=perl%2Fmodules%2FScope-Upper.git;a=blobdiff_plain;f=Upper.xs;h=0c762de1dcb947d420bd265d01231d8cec433d7e;hp=e3713ae95ffccae1ced4042185b620c704947522;hb=HEAD;hpb=181496f2ca2ce70348ee900a89f3e8854958c385

diff --git a/Upper.xs b/Upper.xs
index e3713ae..7be4f69 100644
--- a/Upper.xs
+++ b/Upper.xs
@@ -6,21 +6,18 @@
 #include "perl.h"
 #include "XSUB.h"
 
-#define __PACKAGE__ "Scope::Upper"
+/* --- XS helpers ---------------------------------------------------------- */
 
-#ifndef SU_DEBUG
-# define SU_DEBUG 0
-#endif
+#define XSH_PACKAGE "Scope::Upper"
+
+#include "xsh/caps.h"
+#include "xsh/util.h"
+#include "xsh/debug.h"
 
 /* --- Compatibility ------------------------------------------------------- */
 
-#ifndef NOOP
-# define NOOP
-#endif
-
-#ifndef dNOOP
-# define dNOOP
-#endif
+/* perl 5.23.8 onwards has a revamped context system */
+#define SU_HAS_NEW_CXT XSH_HAS_PERL(5, 23, 8)
 
 #ifndef dVAR
 # define dVAR dNOOP
@@ -42,20 +39,6 @@
 # define PERL_UNUSED_VAR(V)
 #endif
 
-#ifndef STMT_START
-# define STMT_START do
-#endif
-
-#ifndef STMT_END
-# define STMT_END while (0)
-#endif
-
-#if SU_DEBUG
-# define SU_D(X) STMT_START X STMT_END
-#else
-# define SU_D(X)
-#endif
-
 #ifndef Newx
 # define Newx(v, n, c) New(0, v, n, c)
 #endif
@@ -217,44 +200,10 @@ static U8 su_op_gimme_reverse(U8 gimme) {
 # define NEGATIVE_INDICES_VAR "NEGATIVE_INDICES"
 #endif
 
-#define SU_HAS_PERL(R, V, S) (PERL_REVISION > (R) || (PERL_REVISION == (R) && (PERL_VERSION > (V) || (PERL_VERSION == (V) && (PERL_SUBVERSION >= (S))))))
-#define SU_HAS_PERL_EXACT(R, V, S) ((PERL_REVISION == (R)) && (PERL_VERSION == (V)) && (PERL_SUBVERSION == (S)))
+/* --- Error messages ------------------------------------------------------ */
 
-/* --- Threads and multiplicity -------------------------------------------- */
-
-#ifndef SU_MULTIPLICITY
-# if defined(MULTIPLICITY) || defined(PERL_IMPLICIT_CONTEXT)
-#  define SU_MULTIPLICITY 1
-# else
-#  define SU_MULTIPLICITY 0
-# endif
-#endif
-#if SU_MULTIPLICITY && !defined(tTHX)
-# define tTHX PerlInterpreter*
-#endif
-
-#if SU_MULTIPLICITY && defined(USE_ITHREADS) && defined(dMY_CXT) && defined(MY_CXT) && defined(START_MY_CXT) && defined(MY_CXT_INIT) && (defined(MY_CXT_CLONE) || defined(dMY_CXT_SV))
-# define SU_THREADSAFE 1
-# ifndef MY_CXT_CLONE
-#  define MY_CXT_CLONE \
-    dMY_CXT_SV;                                                      \
-    my_cxt_t *my_cxtp = (my_cxt_t*)SvPVX(newSV(sizeof(my_cxt_t)-1)); \
-    Copy(INT2PTR(my_cxt_t*, SvUV(my_cxt_sv)), my_cxtp, 1, my_cxt_t); \
-    sv_setuv(my_cxt_sv, PTR2UV(my_cxtp))
-# endif
-#else
-# define SU_THREADSAFE 0
-# undef  dMY_CXT
-# define dMY_CXT      dNOOP
-# undef  MY_CXT
-# define MY_CXT       su_globaldata
-# undef  START_MY_CXT
-# define START_MY_CXT static my_cxt_t MY_CXT;
-# undef  MY_CXT_INIT
-# define MY_CXT_INIT  NOOP
-# undef  MY_CXT_CLONE
-# define MY_CXT_CLONE NOOP
-#endif
+static const char su_stack_smash[]    = "Cannot target a scope outside of the current stack";
+static const char su_no_such_target[] = "No targetable %s scope in the current stack";
 
 /* --- Unique context ID global storage ------------------------------------ */
 
@@ -271,22 +220,14 @@ static su_uv_array su_uid_seq_counter;
 
 static perl_mutex su_uid_seq_counter_mutex;
 
-#define SU_LOCK(M)   MUTEX_LOCK(M)
-#define SU_UNLOCK(M) MUTEX_UNLOCK(M)
-
-#else /* USE_ITHREADS */
-
-#define SU_LOCK(M)
-#define SU_UNLOCK(M)
-
-#endif /* !USE_ITHREADS */
+#endif /* USE_ITHREADS */
 
 static UV su_uid_seq_next(pTHX_ UV depth) {
 #define su_uid_seq_next(D) su_uid_seq_next(aTHX_ (D))
  UV seq;
  UV *seqs;
 
- SU_LOCK(&su_uid_seq_counter_mutex);
+ XSH_LOCK(&su_uid_seq_counter_mutex);
 
  seqs = su_uid_seq_counter.seqs;
 
@@ -303,7 +244,7 @@ static UV su_uid_seq_next(pTHX_ UV depth) {
 
  seq = ++seqs[depth];
 
- SU_UNLOCK(&su_uid_seq_counter_mutex);
+ XSH_UNLOCK(&su_uid_seq_counter_mutex);
 
  return seq;
 }
@@ -330,53 +271,47 @@ static UV su_uid_depth(pTHX_ I32 cxix) {
 }
 
 typedef struct {
- su_uid **map;
- STRLEN   used;
- STRLEN   alloc;
+ su_uid *map;
+ STRLEN  used;
+ STRLEN  alloc;
 } su_uid_storage;
 
 static void su_uid_storage_dup(pTHX_ su_uid_storage *new_cxt, const su_uid_storage *old_cxt, UV max_depth) {
 #define su_uid_storage_dup(N, O, D) su_uid_storage_dup(aTHX_ (N), (O), (D))
- su_uid **old_map = old_cxt->map;
+ su_uid *old_map = old_cxt->map;
 
  if (old_map) {
-  su_uid **new_map = new_cxt->map;
-  STRLEN old_used  = old_cxt->used;
-  STRLEN new_used, new_alloc;
-  STRLEN i;
+  su_uid *new_map  = new_cxt->map;
+  STRLEN  old_used = old_cxt->used;
+  STRLEN  new_used, new_alloc;
+  STRLEN  i;
 
-  new_used = max_depth < old_used ? max_depth : old_used;
+  new_used      = max_depth < old_used ? max_depth : old_used;
   new_cxt->used = new_used;
 
-  if (new_used <= new_cxt->alloc)
-   new_alloc = new_cxt->alloc;
-  else {
-   new_alloc = new_used;
-   Renew(new_map, new_alloc, su_uid *);
-   for (i = new_cxt->alloc; i < new_alloc; ++i)
-    new_map[i] = NULL;
+  if (new_used <= new_cxt->alloc) {
+   new_alloc      = new_cxt->alloc;
+  } else {
+   new_alloc      = new_used;
+   Renew(new_map, new_alloc, su_uid);
    new_cxt->map   = new_map;
    new_cxt->alloc = new_alloc;
   }
 
   for (i = 0; i < new_alloc; ++i) {
-   su_uid *new_uid = new_map[i];
+   su_uid *new_uid = new_map + i;
 
    if (i < new_used) { /* => i < max_depth && i < old_used */
-    su_uid *old_uid = old_map[i];
+    su_uid *old_uid = old_map + i;
 
     if (old_uid && (old_uid->flags & SU_UID_ACTIVE)) {
-     if (!new_uid) {
-      Newx(new_uid, 1, su_uid);
-      new_map[i] = new_uid;
-     }
      *new_uid = *old_uid;
      continue;
     }
    }
 
-   if (new_uid)
-    new_uid->flags &= ~SU_UID_ACTIVE;
+   new_uid->seq   = 0;
+   new_uid->flags = 0;
   }
  }
 
@@ -405,7 +340,7 @@ typedef struct {
 
 /* --- uplevel() data tokens and global storage ---------------------------- */
 
-#define SU_UPLEVEL_HIJACKS_RUNOPS SU_HAS_PERL(5, 8, 0)
+#define SU_UPLEVEL_HIJACKS_RUNOPS XSH_HAS_PERL(5, 8, 0)
 
 typedef struct {
  void          *next;
@@ -415,27 +350,39 @@ typedef struct {
 
  I32            cxix;
 
- I32            target_depth;
- CV            *target;
-
  CV            *callback;
  CV            *renamed;
 
+#if SU_HAS_NEW_CXT
+ U8             *cxtypes; /* array of saved context types */
+ I32            gap;      /* how many contexts have temporarily CXt_NULLed out*/
+ AV*            argarray; /* the PL_curpad[0] of the uplevel sub */
+#else
+ I32            target_depth;
+ CV            *target;
  PERL_SI       *si;
  PERL_SI       *old_curstackinfo;
  AV            *old_mainstack;
+ OP            *old_op;
+ bool           old_catch;
+ bool           died;
+#endif
 
  COP           *old_curcop;
 
- OP            *old_op;
 #if SU_UPLEVEL_HIJACKS_RUNOPS
  runops_proc_t  old_runops;
 #endif
- bool           old_catch;
-
- bool           died;
 } su_uplevel_ud;
 
+#if SU_HAS_NEW_CXT
+/* used to flag a context stack entry whose type has been temporarily
+ * set to CXt_NULL. It relies on perl not using this value for real
+ * CXt_NULL entries.
+ */
+# define CXp_SU_UPLEVEL_NULLED 0x20
+#endif
+
 static su_uplevel_ud *su_uplevel_ud_new(pTHX) {
 #define su_uplevel_ud_new() su_uplevel_ud_new(aTHX)
  su_uplevel_ud *sud;
@@ -448,35 +395,31 @@ static su_uplevel_ud *su_uplevel_ud_new(pTHX) {
  sud->tmp_uid_storage.used  = 0;
  sud->tmp_uid_storage.alloc = 0;
 
+#if !SU_HAS_NEW_CXT
  Newx(si, 1, PERL_SI);
  si->si_stack   = newAV();
  AvREAL_off(si->si_stack);
  si->si_cxstack = NULL;
- si->si_cxmax   = 0;
+ si->si_cxmax   = -1;
 
  sud->si = si;
+#endif
 
  return sud;
 }
 
 static void su_uplevel_ud_delete(pTHX_ su_uplevel_ud *sud) {
 #define su_uplevel_ud_delete(S) su_uplevel_ud_delete(aTHX_ (S))
+
+#if !SU_HAS_NEW_CXT
  PERL_SI *si = sud->si;
 
  Safefree(si->si_cxstack);
  SvREFCNT_dec(si->si_stack);
  Safefree(si);
+#endif
 
- if (sud->tmp_uid_storage.map) {
-  su_uid **map   = sud->tmp_uid_storage.map;
-  STRLEN   alloc = sud->tmp_uid_storage.alloc;
-  STRLEN   i;
-
-  for (i = 0; i < alloc; ++i)
-   Safefree(map[i]);
-
-  Safefree(map);
- }
+ Safefree(sud->tmp_uid_storage.map);
 
  Safefree(sud);
 
@@ -495,61 +438,97 @@ typedef struct {
 
 /* --- Global data --------------------------------------------------------- */
 
-#define MY_CXT_KEY __PACKAGE__ "::_guts" XS_VERSION
-
 typedef struct {
- char               *stack_placeholder;
  su_unwind_storage   unwind_storage;
  su_yield_storage    yield_storage;
  su_uplevel_storage  uplevel_storage;
  su_uid_storage      uid_storage;
-} my_cxt_t;
+} xsh_user_cxt_t;
+
+#define XSH_THREADS_USER_CONTEXT            1
+#define XSH_THREADS_USER_CLONE_NEEDS_DUP    0
+#define XSH_THREADS_COMPILE_TIME_PROTECTION 0
+
+#if XSH_THREADSAFE
+
+static void xsh_user_clone(pTHX_ const xsh_user_cxt_t *old_cxt, xsh_user_cxt_t *new_cxt) {
+ new_cxt->uplevel_storage.top   = NULL;
+ new_cxt->uplevel_storage.root  = NULL;
+ new_cxt->uplevel_storage.count = 0;
+ new_cxt->uid_storage.map   = NULL;
+ new_cxt->uid_storage.used  = 0;
+ new_cxt->uid_storage.alloc = 0;
+
+ su_uid_storage_dup(&new_cxt->uid_storage, &old_cxt->uid_storage,
+                    old_cxt->uid_storage.used);
 
-START_MY_CXT
+ return;
+}
+
+#endif /* XSH_THREADSAFE */
+
+#include "xsh/threads.h"
 
 /* --- Stack manipulations ------------------------------------------------- */
 
-#define SU_SAVE_PLACEHOLDER() save_pptr(&MY_CXT.stack_placeholder)
+/* how many slots on the save stack various save types take up */
+
+#define SU_SAVE_DESTRUCTOR_SIZE 3 /* SAVEt_DESTRUCTOR_X */
+#define SU_SAVE_SCALAR_SIZE     3 /* SAVEt_SV */
+#define SU_SAVE_ARY_SIZE        3 /* SAVEt_AV */
+#define SU_SAVE_AELEM_SIZE      4 /* SAVEt_AELEM */
+#define SU_SAVE_HASH_SIZE       3 /* SAVEt_HV */
+#define SU_SAVE_HELEM_SIZE      4 /* SAVEt_HELEM */
+#define SU_SAVE_HDELETE_SIZE    4 /* SAVEt_DELETE */
 
-#define SU_SAVE_DESTRUCTOR_SIZE  3
-#define SU_SAVE_PLACEHOLDER_SIZE 3
+#define SU_SAVE_GVCV_SIZE       SU_SAVE_DESTRUCTOR_SIZE
 
-#define SU_SAVE_SCALAR_SIZE 3
+/* the overhead of save_alloc() but not including any elements,
+ * of which there must be at least 1 */
+#if XSH_HAS_PERL(5, 14, 0)
+# define SU_SAVE_ALLOC_SIZE      1 /* SAVEt_ALLOC */
+#else
+# define SU_SAVE_ALLOC_SIZE      2 /* SAVEt_ALLOC */
+#endif
 
-#define SU_SAVE_ARY_SIZE      3
-#define SU_SAVE_AELEM_SIZE    4
 #ifdef SAVEADELETE
-# define SU_SAVE_ADELETE_SIZE 3
+# define SU_SAVE_ADELETE_SIZE   3 /* SAVEt_ADELETE */
 #else
-# define SU_SAVE_ADELETE_SIZE SU_SAVE_DESTRUCTOR_SIZE
+# define SU_SAVE_ADELETE_SIZE   SU_SAVE_DESTRUCTOR_SIZE
+#endif
+
+/* (NB: it was 4 between 5.13.1 and 5.13.7) */
+#if XSH_HAS_PERL(5, 8, 9)
+# define SU_SAVE_GP_SIZE        3 /* SAVEt_GP */
+# else
+# define SU_SAVE_GP_SIZE        6 /* SAVEt_GP */
 #endif
+
+/* sometimes we don't know in advance whether we're saving or deleting
+ * an array/hash element. So include enough room for a variable-sized
+ * save_alloc() to pad it to a fixed size.
+ */
+
 #if SU_SAVE_AELEM_SIZE < SU_SAVE_ADELETE_SIZE
-# define SU_SAVE_AELEM_OR_ADELETE_SIZE SU_SAVE_ADELETE_SIZE
+# define SU_SAVE_AELEM_OR_ADELETE_SIZE \
+    (SU_SAVE_ADELETE_SIZE + SU_SAVE_ALLOC_SIZE + 1)
+#elif SU_SAVE_AELEM_SIZE > SU_SAVE_ADELETE_SIZE
+# define SU_SAVE_AELEM_OR_ADELETE_SIZE \
+    (SU_SAVE_AELEM_SIZE + SU_SAVE_ALLOC_SIZE + 1)
 #else
 # define SU_SAVE_AELEM_OR_ADELETE_SIZE SU_SAVE_AELEM_SIZE
 #endif
 
-#define SU_SAVE_HASH_SIZE    3
-#define SU_SAVE_HELEM_SIZE   4
-#define SU_SAVE_HDELETE_SIZE 4
 #if SU_SAVE_HELEM_SIZE < SU_SAVE_HDELETE_SIZE
-# define SU_SAVE_HELEM_OR_HDELETE_SIZE SU_SAVE_HDELETE_SIZE
+# define SU_SAVE_HELEM_OR_HDELETE_SIZE \
+    (SU_SAVE_HDELETE_SIZE + SU_SAVE_ALLOC_SIZE + 1)
+#elif SU_SAVE_HELEM_SIZE > SU_SAVE_HDELETE_SIZE
+# define SU_SAVE_HELEM_OR_HDELETE_SIZE \
+    (SU_SAVE_HELEM_SIZE + SU_SAVE_ALLOC_SIZE + 1)
 #else
 # define SU_SAVE_HELEM_OR_HDELETE_SIZE SU_SAVE_HELEM_SIZE
 #endif
 
-#define SU_SAVE_GVCV_SIZE SU_SAVE_DESTRUCTOR_SIZE
-
-#if !SU_HAS_PERL(5, 8, 9)
-# define SU_SAVE_GP_SIZE 6
-#elif !SU_HAS_PERL(5, 13, 0) || (SU_RELEASE && SU_HAS_PERL_EXACT(5, 13, 0))
-# define SU_SAVE_GP_SIZE 3
-#elif !SU_HAS_PERL(5, 13, 8)
-# define SU_SAVE_GP_SIZE 4
-#else
-# define SU_SAVE_GP_SIZE 3
-#endif
-
 #ifndef SvCANEXISTDELETE
 # define SvCANEXISTDELETE(sv) \
   (!SvRMAGICAL(sv)            \
@@ -571,13 +550,14 @@ static I32 su_av_key2idx(pTHX_ AV *av, I32 key) {
   return key;
 
 /* Added by MJD in perl-5.8.1 with 6f12eb6d2a1dfaf441504d869b27d2e40ef4966a */
-#if SU_HAS_PERL(5, 8, 1)
+#if XSH_HAS_PERL(5, 8, 1)
  if (SvRMAGICAL(av)) {
   const MAGIC * const tied_magic = mg_find((SV *) av, PERL_MAGIC_tied);
   if (tied_magic) {
-   SV * const * const negative_indices_glob =
-                    hv_fetch(SvSTASH(SvRV(SvTIED_obj((SV *) (av), tied_magic))),
-                             NEGATIVE_INDICES_VAR, 16, 0);
+   SV * const * const negative_indices_glob = hv_fetch(
+    SvSTASH(SvRV(SvTIED_obj((SV *) (av), tied_magic))),
+    NEGATIVE_INDICES_VAR, sizeof(NEGATIVE_INDICES_VAR)-1, 0
+   );
    if (negative_indices_glob && SvTRUE(GvSV(*negative_indices_glob)))
     return key;
   }
@@ -673,9 +653,9 @@ static void su_save_helem(pTHX_ HV *hv, SV *keysv, SV *val) {
   return;
  }
 
- if (preeminent)
+ if (preeminent) {
   save_helem(hv, keysv, svp);
- else {
+ } else {
   STRLEN keylen;
   const char * const key = SvPV_const(keysv, keylen);
   SAVEDELETE(hv, savepvn(key, keylen),
@@ -691,7 +671,7 @@ static void su_save_helem(pTHX_ HV *hv, SV *keysv, SV *val) {
 
 /* ... Saving code slots from a glob ....................................... */
 
-#if !SU_HAS_PERL(5, 10, 0) && !defined(mro_method_changed_in)
+#if !XSH_HAS_PERL(5, 10, 0) && !defined(mro_method_changed_in)
 # define mro_method_changed_in(G) PL_sub_generation++
 #endif
 
@@ -729,16 +709,26 @@ static void su_save_gvcv(pTHX_ GV *gv) {
 /* --- Actions ------------------------------------------------------------- */
 
 typedef struct {
- I32 depth;
- I32 pad;
- I32 *origin;
- void (*handler)(pTHX_ void *);
+ I32 orig_ix; /* original savestack_ix */
+ I32 offset;  /* how much we bumped this savestack index */
+} su_ud_origin_elem;
+
+typedef struct {
+ U8                 type;
+ U8                 private;
+ /* spare */
+ I32                depth;
+ su_ud_origin_elem *origin;
 } su_ud_common;
 
+#define SU_UD_TYPE(U)    (((su_ud_common *) (U))->type)
+#define SU_UD_PRIVATE(U) (((su_ud_common *) (U))->private)
 #define SU_UD_DEPTH(U)   (((su_ud_common *) (U))->depth)
-#define SU_UD_PAD(U)     (((su_ud_common *) (U))->pad)
 #define SU_UD_ORIGIN(U)  (((su_ud_common *) (U))->origin)
-#define SU_UD_HANDLER(U) (((su_ud_common *) (U))->handler)
+
+#define SU_UD_TYPE_REAP     0
+#define SU_UD_TYPE_LOCALIZE 1
+#define SU_UD_TYPE_UID      2
 
 #define SU_UD_FREE(U) STMT_START { \
  if (SU_UD_ORIGIN(U)) Safefree(SU_UD_ORIGIN(U)); \
@@ -747,15 +737,16 @@ typedef struct {
 
 /* ... Reap ................................................................ */
 
-#define SU_SAVE_LAST_CX (!SU_HAS_PERL(5, 8, 4) || (SU_HAS_PERL(5, 9, 5) && !SU_HAS_PERL(5, 14, 0)) || SU_HAS_PERL(5, 15, 0))
+#define SU_SAVE_LAST_CX (!XSH_HAS_PERL(5, 8, 4) || (XSH_HAS_PERL(5, 9, 5) && !XSH_HAS_PERL(5, 14, 0)) || XSH_HAS_PERL(5, 15, 0))
 
 typedef struct {
  su_ud_common ci;
- SV *cb;
+ SV          *cb;
 } su_ud_reap;
 
-static void su_call(pTHX_ void *ud_) {
- su_ud_reap *ud = (su_ud_reap *) ud_;
+#define SU_UD_REAP_CB(U) (((su_ud_reap *) (U))->cb)
+
+static void su_call(pTHX_ SV *cb) {
 #if SU_SAVE_LAST_CX
  I32 cxix;
  PERL_CONTEXT saved_cx;
@@ -763,11 +754,8 @@ static void su_call(pTHX_ void *ud_) {
 
  dSP;
 
- SU_D({
-  PerlIO_printf(Perl_debug_log,
-                "%p: @@@ call\n%p: depth=%2d scope_ix=%2d save_ix=%2d\n",
-                 ud, ud, SU_UD_DEPTH(ud), PL_scopestack_ix, PL_savestack_ix);
- });
+ XSH_D(xsh_debug_log("@@@ call scope_ix=%2d save_ix=%2d\n",
+                          PL_scopestack_ix, PL_savestack_ix));
 
  ENTER;
  SAVETMPS;
@@ -782,7 +770,7 @@ static void su_call(pTHX_ void *ud_) {
  saved_cx = cxstack[cxix];
 #endif /* SU_SAVE_LAST_CX */
 
- call_sv(ud->cb, G_VOID);
+ call_sv(cb, G_VOID);
 
 #if SU_SAVE_LAST_CX
  cxstack[cxix] = saved_cx;
@@ -793,59 +781,58 @@ static void su_call(pTHX_ void *ud_) {
  FREETMPS;
  LEAVE;
 
- SvREFCNT_dec(ud->cb);
- SU_UD_FREE(ud);
-}
-
-static void su_reap(pTHX_ void *ud) {
-#define su_reap(U) su_reap(aTHX_ (U))
- SU_D({
-  PerlIO_printf(Perl_debug_log,
-                "%p: === reap\n%p: depth=%2d scope_ix=%2d save_ix=%2d\n",
-                 ud, ud, SU_UD_DEPTH(ud), PL_scopestack_ix, PL_savestack_ix);
- });
+ SvREFCNT_dec(cb);
 
- SAVEDESTRUCTOR_X(su_call, ud);
+ return;
 }
 
 /* ... Localize & localize array/hash element .............................. */
 
 typedef struct {
  su_ud_common ci;
- SV    *sv;
- SV    *val;
- SV    *elem;
- svtype type;
+ SV          *sv;
+ SV          *val;
+ SV          *elem;
 } su_ud_localize;
 
+#define SU_UD_LOCALIZE_SV(U)   (((su_ud_localize *) (U))->sv)
+#define SU_UD_LOCALIZE_VAL(U)  (((su_ud_localize *) (U))->val)
+#define SU_UD_LOCALIZE_ELEM(U) (((su_ud_localize *) (U))->elem)
+
 #define SU_UD_LOCALIZE_FREE(U) STMT_START { \
- SvREFCNT_dec((U)->elem); \
- SvREFCNT_dec((U)->val);  \
- SvREFCNT_dec((U)->sv);   \
- SU_UD_FREE(U);           \
+ SvREFCNT_dec(SU_UD_LOCALIZE_ELEM(U)); \
+ SvREFCNT_dec(SU_UD_LOCALIZE_VAL(U)); \
+ SvREFCNT_dec(SU_UD_LOCALIZE_SV(U)); \
+ SU_UD_FREE(U); \
 } STMT_END
 
 static I32 su_ud_localize_init(pTHX_ su_ud_localize *ud, SV *sv, SV *val, SV *elem) {
 #define su_ud_localize_init(UD, S, V, E) su_ud_localize_init(aTHX_ (UD), (S), (V), (E))
- UV deref = 0;
- svtype t = SVt_NULL;
- I32 size;
+ int take_ref = 0;
+ svtype     t = SVt_NULL;
+ I32     size;
 
  SvREFCNT_inc_simple_void(sv);
 
  if (SvTYPE(sv) >= SVt_PVGV) {
+  if (SvFAKE(sv)) {
+   sv_force_normal(sv);
+   goto string_spec;
+  }
+
   if (!val || !SvROK(val)) { /* local *x; or local *x = $val; */
    t = SVt_PVGV;
   } else {                   /* local *x = \$val; */
    t = SvTYPE(SvRV(val));
-   deref = 1;
   }
  } else if (SvROK(sv)) {
   croak("Invalid %s reference as the localization target",
                  sv_reftype(SvRV(sv), 0));
  } else {
   STRLEN len, l;
-  const char *p = SvPV_const(sv, len), *s;
+  const char *p, *s;
+string_spec:
+  p = SvPV_const(sv, len);
   for (s = p, l = len; l > 0 && isSPACE(*s); ++s, --l) { }
   if (!l) {
    l = len;
@@ -861,14 +848,17 @@ static I32 su_ud_localize_init(pTHX_ su_ud_localize *ud, SV *sv, SV *val, SV *el
   if (t != SVt_NULL) {
    ++s;
    --l;
+   if (t == SVt_PV)
+    take_ref = 1;
   } else if (val) { /* t == SVt_NULL, type can't be inferred from the sigil */
    if (SvROK(val) && !sv_isobject(val)) {
     t = SvTYPE(SvRV(val));
-    deref = 1;
    } else {
     t = SvTYPE(val);
+    take_ref = 1;
    }
   }
+
   SvREFCNT_dec(sv);
   sv = newSVpvn(s, l);
  }
@@ -877,31 +867,32 @@ static I32 su_ud_localize_init(pTHX_ su_ud_localize *ud, SV *sv, SV *val, SV *el
   case SVt_PVAV:
    size  = elem ? SU_SAVE_AELEM_OR_ADELETE_SIZE
                 : SU_SAVE_ARY_SIZE;
-   deref = 0;
    break;
   case SVt_PVHV:
    size  = elem ? SU_SAVE_HELEM_OR_HDELETE_SIZE
                 : SU_SAVE_HASH_SIZE;
-   deref = 0;
    break;
   case SVt_PVGV:
    size  = SU_SAVE_GP_SIZE;
-   deref = 0;
    break;
   case SVt_PVCV:
    size  = SU_SAVE_GVCV_SIZE;
-   deref = 0;
    break;
   default:
    size = SU_SAVE_SCALAR_SIZE;
    break;
  }
- /* When deref is set, val isn't NULL */
+
+ SU_UD_PRIVATE(ud) = t;
 
  ud->sv   = sv;
- ud->val  = val ? newSVsv(deref ? SvRV(val) : val) : NULL;
+ if (val) {
+  val     = newSVsv(val);
+  ud->val = take_ref ? newRV_noinc(val) : val;
+ } else {
+  ud->val = NULL;
+ }
  ud->elem = SvREFCNT_inc(elem);
- ud->type = t;
 
  return size;
 }
@@ -912,28 +903,41 @@ static void su_localize(pTHX_ void *ud_) {
  SV *sv   = ud->sv;
  SV *val  = ud->val;
  SV *elem = ud->elem;
- svtype t = ud->type;
+ svtype t = SU_UD_PRIVATE(ud);
  GV *gv;
 
  if (SvTYPE(sv) >= SVt_PVGV) {
   gv = (GV *) sv;
  } else {
+/* new perl context implementation frees savestack *before* restoring
+ * PL_curcop. Temporarily restore it prematurely to make gv_fetch*
+ * looks up unqualified var names in the caller's package */
+#if SU_HAS_NEW_CXT
+  COP *old_cop = PL_curcop;
+  PL_curcop    = CX_CUR()->blk_oldcop;
+#endif
+
 #ifdef gv_fetchsv
   gv = gv_fetchsv(sv, GV_ADDMULTI, t);
 #else
-  STRLEN len;
-  const char *name = SvPV_const(sv, len);
-  gv = gv_fetchpvn_flags(name, len, GV_ADDMULTI, t);
+  {
+   STRLEN len;
+   const char *name = SvPV_const(sv, len);
+   gv = gv_fetchpvn_flags(name, len, GV_ADDMULTI, t);
+  }
+#endif
+
+#if SU_HAS_NEW_CXT
+  CX_CUR()->blk_oldcop = old_cop;
 #endif
  }
 
- SU_D({
+ XSH_D({
   SV *z = newSV(0);
   SvUPGRADE(z, t);
-  PerlIO_printf(Perl_debug_log, "%p: === localize a %s\n",ud, sv_reftype(z, 0));
-  PerlIO_printf(Perl_debug_log,
-                "%p: depth=%2d scope_ix=%2d save_ix=%2d\n",
-                 ud, SU_UD_DEPTH(ud), PL_scopestack_ix, PL_savestack_ix);
+  xsh_debug_log("%p:     === localize a %s\n", ud, sv_reftype(z, 0));
+  xsh_debug_log("%p:         depth=%2d scope_ix=%2d save_ix=%2d\n",
+                 ud,   SU_UD_DEPTH(ud), PL_scopestack_ix, PL_savestack_ix);
   SvREFCNT_dec(z);
  });
 
@@ -942,16 +946,18 @@ static void su_localize(pTHX_ void *ud_) {
   case SVt_PVAV:
    if (elem) {
     su_save_aelem(GvAV(gv), elem, val);
-    goto done;
-   } else
+    return;
+   } else {
     save_ary(gv);
+   }
    break;
   case SVt_PVHV:
    if (elem) {
     su_save_helem(GvHV(gv), elem, val);
-    goto done;
-   } else
+    return;
+   } else {
     save_hash(gv);
+   }
    break;
   case SVt_PVGV:
    save_gp(gv, 1); /* hide previous entry in symtab */
@@ -960,51 +966,84 @@ static void su_localize(pTHX_ void *ud_) {
    su_save_gvcv(gv);
    break;
   default:
-   gv = (GV *) save_scalar(gv);
+   save_scalar(gv);
    break;
  }
 
  if (val)
   SvSetMagicSV((SV *) gv, val);
 
-done:
- SU_UD_LOCALIZE_FREE(ud);
+ return;
+}
+
+/* ... Unique context ID ................................................... */
+
+/* We must pass the index because XSH_CXT.uid_storage might be reallocated
+ * between the UID fetch and the invalidation at the end of scope. */
+
+typedef struct {
+ su_ud_common ci;
+ I32          idx;
+} su_ud_uid;
+
+static void su_uid_drop(pTHX_ void *ud_) {
+ su_ud_uid *ud = ud_;
+ dXSH_CXT;
+
+ XSH_CXT.uid_storage.map[ud->idx].flags &= ~SU_UID_ACTIVE;
+
+ SU_UD_FREE(ud);
+
+ return;
 }
 
 /* --- Pop a context back -------------------------------------------------- */
 
 #ifdef DEBUGGING
-# define SU_CXNAME(C) PL_block_type[CxTYPE(C)]
+# define SU_CX_TYPENAME(T) PL_block_type[(T)]
 #else
-# if SU_HAS_PERL(5, 11, 0)
+# if XSH_HAS_PERL(5, 23, 8)
 static const char *su_block_type[] = {
  "NULL",
  "WHEN",
  "BLOCK",
  "GIVEN",
- "LOOP_FOR",
- "LOOP_PLAIN",
+ "LOOP_ARY",
  "LOOP_LAZYSV",
  "LOOP_LAZYIV",
+ "LOOP_LIST",
+ "LOOP_PLAIN",
  "SUB",
  "FORMAT",
  "EVAL",
  "SUBST"
 };
-# elif SU_HAS_PERL(5, 9, 3)
+# elif XSH_HAS_PERL(5, 11, 0)
 static const char *su_block_type[] = {
  "NULL",
- "SUB",
- "EVAL",
  "WHEN",
- "SUBST",
  "BLOCK",
- "FORMAT",
  "GIVEN",
  "LOOP_FOR",
  "LOOP_PLAIN",
  "LOOP_LAZYSV",
- "LOOP_LAZYIV"
+ "LOOP_LAZYIV",
+ "SUB",
+ "FORMAT",
+ "EVAL",
+ "SUBST"
+};
+# elif XSH_HAS_PERL(5, 10, 0)
+static const char *su_block_type[] = {
+ "NULL",
+ "SUB",
+ "EVAL",
+ "LOOP",
+ "SUBST",
+ "BLOCK",
+ "FORMAT"
+ "WHEN",
+ "GIVEN"
 };
 # else
 static const char *su_block_type[] = {
@@ -1013,186 +1052,317 @@ static const char *su_block_type[] = {
  "EVAL",
  "LOOP",
  "SUBST",
- "BLOCK"
+ "BLOCK",
+ "FORMAT"
 };
 # endif
-# define SU_CXNAME(C) su_block_type[CxTYPE(C)]
+# define SU_CX_TYPENAME(T) su_block_type[(T)]
 #endif
 
+#define SU_CXNAME(C) SU_CX_TYPENAME(CxTYPE(C))
+
+#if XSH_DEBUG
+
+/* for debugging. These indicate how many ENTERs each context type
+ * does before the PUSHBLOCK */
+
+static const int su_cxt_enter_count[] = {
+# if XSH_HAS_PERL(5, 23, 8)
+  0 /* context pushes no longer do ENTERs */
+# elif XSH_HAS_PERL(5, 11, 0)
+ /* NULL WHEN BLOCK GIVEN LOOP_FOR LOOP_PLAIN LOOP_LAZYSV
+  * LOOP_LAZYIV SUB FORMAT EVAL SUBST */
+ 0, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1, 0
+# elif XSH_HAS_PERL(5, 10, 0)
+ /* NULL SUB EVAL LOOP SUBST BLOCK FORMAT WHEN GIVEN */
+ 0, 1, 1, 2, 0, 1, 1, 1, 1
+# else
+ /* NULL SUB EVAL LOOP SUBST BLOCK FORMAT */
+ 0, 1, 1, 2, 0, 1, 1
+# endif
+};
+
+#endif /* XSH_DEBUG */
+
+/* push at least 'size' slots worth of padding onto the savestack */
+
+static void su_ss_push_padding(pTHX_ void *ud, I32 size) {
+#define su_ss_push_padding(U, S) su_ss_push_padding(aTHX_ (U), (S))
+ if (size <= 0)
+  return;
+
+ if (size < SU_SAVE_ALLOC_SIZE + 1) /* minimum possible SAVEt_ALLOC */
+  size = SU_SAVE_ALLOC_SIZE + 1;
+
+ XSH_D(xsh_debug_log(
+       "%p:     push %2d padding at save_ix=%d\n",
+        ud,         size,      PL_savestack_ix));
+
+ save_alloc((size - SU_SAVE_ALLOC_SIZE) * sizeof(*PL_savestack), 0);
+
+ return;
+}
+
+static void su_pop(pTHX_ void *ud);
+
+/* push an su_pop destructor onto the savestack with suitable padding.
+ * first indicates that this is the first push of a destructor */
+
+static void su_ss_push_destructor(pTHX_ void *ud, I32 depth, bool first) {
+#define su_ss_push_destructor(U, D, F) su_ss_push_destructor(aTHX_ (U), (D), (F))
+ su_ud_origin_elem *origin = SU_UD_ORIGIN(ud);
+
+ assert(first || origin[depth+1].orig_ix == PL_savestack_ix);
+
+ su_ss_push_padding(ud,
+              (origin[depth].orig_ix + origin[depth].offset) - PL_savestack_ix);
+
+ XSH_D(xsh_debug_log(
+       "%p:     push destructor at save_ix=%d depth=%d scope_ix=%d\n",
+        ud,                   PL_savestack_ix,   depth, PL_scopestack_ix));
+
+ SAVEDESTRUCTOR_X(su_pop, ud);
+
+ assert(first ||
+        PL_savestack_ix <= origin[depth+1].orig_ix + origin[depth+1].offset);
+
+ return;
+}
+
+/* this is called during each leave_scope() via SAVEDESTRUCTOR_X */
+
 static void su_pop(pTHX_ void *ud) {
 #define su_pop(U) su_pop(aTHX_ (U))
- I32 depth, base, mark, *origin;
- depth = SU_UD_DEPTH(ud);
-
- SU_D(
-  PerlIO_printf(Perl_debug_log,
-   "%p: --- pop a %s\n"
-   "%p: leave scope     at depth=%2d scope_ix=%2d cur_top=%2d cur_base=%2d\n",
-    ud, SU_CXNAME(cxstack + cxstack_ix),
-    ud, depth, PL_scopestack_ix,PL_savestack_ix,PL_scopestack[PL_scopestack_ix])
- );
+ I32 depth, base, mark;
+ su_ud_origin_elem *origin;
 
+ depth  = SU_UD_DEPTH(ud);
  origin = SU_UD_ORIGIN(ud);
- mark   = origin[depth];
- base   = origin[depth - 1];
 
- SU_D(PerlIO_printf(Perl_debug_log,
-                    "%p: original scope was %*c top=%2d     base=%2d\n",
-                     ud,                24, ' ',    mark,        base));
+ XSH_D(xsh_debug_log("%p: ### su_pop: depth=%d\n", ud, depth));
 
- if (base < mark) {
-#if SU_HAS_PERL(5, 19, 4)
-  I32 save = -1;
-  PERL_CONTEXT *cx;
-#endif
-
-  SU_D(PerlIO_printf(Perl_debug_log, "%p: clear leftovers\n", ud));
+ depth--;
+ mark = PL_savestack_ix;
+ base = origin[depth].orig_ix;
 
-#if SU_HAS_PERL(5, 19, 4)
-  cx = cxstack + cxstack_ix;
-  if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT)
-   save = PL_scopestack[cx->blk_oldscopesp - 1];
-#endif
+ XSH_D(xsh_debug_log("%p:     residual savestack frame is %d(+%d)..%d\n",
+                      ud,                  base, origin[depth].offset, mark));
 
-  PL_savestack_ix = mark;
+ if (base < mark) {
+  XSH_D(xsh_debug_log("%p:     clear leftovers at %d..%d\n", ud, base, mark));
   leave_scope(base);
-
-#if SU_HAS_PERL(5, 19, 4)
-  if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT)
-   PL_scopestack[cx->blk_oldscopesp - 1] = save;
-#endif
  }
- PL_savestack_ix = base;
+ assert(PL_savestack_ix == base);
 
- SU_UD_DEPTH(ud) = --depth;
+ SU_UD_DEPTH(ud) = depth;
 
  if (depth > 0) {
-  I32 pad;
-
-  if ((pad = SU_UD_PAD(ud))) {
-   dMY_CXT;
-   do {
-    SU_D(PerlIO_printf(Perl_debug_log,
-          "%p: push a pad slot at depth=%2d scope_ix=%2d save_ix=%2d\n",
-           ud,                       depth, PL_scopestack_ix, PL_savestack_ix));
-    SU_SAVE_PLACEHOLDER();
-   } while (--pad);
-  }
-
-  SU_D(PerlIO_printf(Perl_debug_log,
-          "%p: push destructor at depth=%2d scope_ix=%2d save_ix=%2d\n",
-           ud,                       depth, PL_scopestack_ix, PL_savestack_ix));
-  SAVEDESTRUCTOR_X(su_pop, ud);
+  su_ss_push_destructor(ud, depth-1, 0);
  } else {
-  SU_UD_HANDLER(ud)(aTHX_ ud);
+  I32 offset = origin[0].offset; /* grab value before origin is freed */
+  switch (SU_UD_TYPE(ud)) {
+   case SU_UD_TYPE_REAP: {
+    XSH_D(
+     xsh_debug_log("%p:     === reap\n%p: depth=%d scope_ix=%d save_ix=%d\n",
+                    ud, ud, SU_UD_DEPTH(ud), PL_scopestack_ix, PL_savestack_ix)
+    );
+    SAVEDESTRUCTOR_X(su_call, SU_UD_REAP_CB(ud));
+    SU_UD_FREE(ud);
+    break;
+   }
+   case SU_UD_TYPE_LOCALIZE:
+    su_localize(ud);
+    SU_UD_LOCALIZE_FREE(ud);
+    break;
+   case SU_UD_TYPE_UID:
+    SAVEDESTRUCTOR_X(su_uid_drop, ud);
+    break;
+  }
+  /* perl 5.23.8 onwards is very fussy about the return from leave_scope()
+   * leaving PL_savestack_ix where it expects it to be */
+  if (PL_savestack_ix < base + offset) {
+   I32 gap = (base + offset) - PL_savestack_ix;
+   assert(gap >= SU_SAVE_ALLOC_SIZE + 1);
+   su_ss_push_padding(ud, gap);
+  }
+  assert(PL_savestack_ix == base + offset);
  }
 
- SU_D(PerlIO_printf(Perl_debug_log,
-                    "%p: --- end pop: cur_top=%2d == cur_base=%2d\n",
-                     ud, PL_savestack_ix, PL_scopestack[PL_scopestack_ix]));
+ XSH_D(xsh_debug_log("%p:     end pop: ss_ix=%d\n", ud, PL_savestack_ix));
 }
 
 /* --- Initialize the stack and the action userdata ------------------------ */
 
-static I32 su_init(pTHX_ void *ud, I32 cxix, I32 size) {
+static void su_init(pTHX_ void *ud, I32 cxix, I32 size) {
 #define su_init(U, C, S) su_init(aTHX_ (U), (C), (S))
- I32 i, depth = 1, pad, offset, base, *origin;
+ su_ud_origin_elem *origin;
+ I32                i, depth;
+ I32                cur_cx_ix, cur_scope_ix;
+
+ XSH_D(xsh_debug_log("%p: ### su_init(cxix=%d, size=%d)\n", ud, cxix, size));
+
+ depth  = PL_scopestack_ix - cxstack[cxix].blk_oldscopesp;
+#if SU_HAS_NEW_CXT
+ depth += (cxstack_ix - cxix); /* each context frame holds 1 scope */
+#endif
+ XSH_D(xsh_debug_log(
+   "%p:     going down by depth=%d with scope_ix=%d save_ix=%d\n",
+    ud, depth, PL_scopestack_ix, PL_savestack_ix));
+
+ /* Artificially increase the position of each savestack frame boundary
+  * to make space to squeeze in a 'size' sized entry (first one) or a
+  * SU_SAVE_DESTRUCTOR_SIZE sized entry (higher ones). In addition, make
+  * sure that each boundary is higher than the previous, so that *every*
+  * scope exit triggers a call to leave_scope(). Each scope exit will call
+  * the su_pop() destructor, which is responsible for: freeing any
+  * savestack entries below the artificially raised floor; then pushing a
+  * new destructor in that space. On the final pop, the "real" savestack
+  * action is pushed rather than another destructor.
+  *
+  * On older perls, savestack frame boundaries are specified by a range of
+  * scopestack entries (one per ENTER). Each scope entry typically does
+  * one or two ENTERs followed by a PUSHBLOCK. Thus the
+  * cx->blku_oldscopesp field set by the PUSHBLOCK points to the next free
+  * slot, which is one above the last of the ENTERs. In the debugging
+  * output we indicate that by bracketing the ENTERs directly preceding
+  * that context push with dashes, e.g.:
+  *
+  *   13b98d8:     ------------------
+  *   13b98d8:                 ENTER origin[0] scope[3] savestack=3+3
+  *   13b98d8:                 ENTER origin[1] scope[4] savestack=9+3
+  *   13b98d8:     cx=1  LOOP_LAZYIV
+  *   13b98d8:     ------------------
+  *
+  * In addition to context stack pushes, other activities can push ENTERs
+  * too, such as grep expr and XS sub calls.
+  *
+  * For newer perls (SU_HAS_NEW_CXT), a context push no longer does any
+  * ENTERs; instead the old savestack position is stored in the new
+  * cx->blk_oldsaveix field; thus this field specifies an additional
+  * savestack frame boundary point in addition to the scopestack entries,
+  * and will also need adjusting.
+  *
+  * We record the original and modified position of each boundary in the
+  * origin array.
+  *
+  * The passed cxix argument represents the scope we wish to inject into;
+  * we have to adjust all the savestack frame boundaries above (but not
+  * including) that context.
+  */
+
+ Newx(origin, depth, su_ud_origin_elem);
+
+ cur_cx_ix    = cxix;
+ cur_scope_ix = cxstack[cxix].blk_oldscopesp;
+
+#if SU_HAS_NEW_CXT
+ XSH_D(xsh_debug_log("%p:     cx=%-2d %-11s\n",
+                      ud,   cur_cx_ix, SU_CXNAME(cxstack+cur_cx_ix)));
+ cur_cx_ix++;
+#endif
+
+ for (i = 0; cur_scope_ix < PL_scopestack_ix; i++) {
+  I32 *ixp;
+  I32  offset;
+
+#if SU_HAS_NEW_CXT
+
+  if (cur_cx_ix <= cxstack_ix
+      && cur_scope_ix == cxstack[cur_cx_ix].blk_oldscopesp)
+   ixp = &(cxstack[cur_cx_ix++].blk_oldsaveix);
+  else
+   ixp = &PL_scopestack[cur_scope_ix++]; /* an ENTER pushed after cur context */
 
- SU_D(PerlIO_printf(Perl_debug_log, "%p: ### init for cx %d\n", ud, cxix));
+#else
 
- if (size <= SU_SAVE_DESTRUCTOR_SIZE)
-  pad = 0;
- else {
-  I32 extra = size - SU_SAVE_DESTRUCTOR_SIZE;
-  pad = extra / SU_SAVE_PLACEHOLDER_SIZE;
-  if (extra % SU_SAVE_PLACEHOLDER_SIZE)
-   ++pad;
- }
- offset = SU_SAVE_DESTRUCTOR_SIZE + SU_SAVE_PLACEHOLDER_SIZE * pad;
+  XSH_D({
+   if (cur_cx_ix <= cxstack_ix) {
+    if (cur_scope_ix == cxstack[cur_cx_ix].blk_oldscopesp) {
+     xsh_debug_log("%p:     cx=%-2d %s\n%p:     ------------------\n",
+                    ud,   cur_cx_ix, SU_CXNAME(cxstack+cur_cx_ix), ud);
+     cur_cx_ix++;
+    }
+    else if (cur_scope_ix + su_cxt_enter_count[CxTYPE(cxstack+cur_cx_ix)]
+             == cxstack[cur_cx_ix].blk_oldscopesp)
+     xsh_debug_log("%p:     ------------------\n", ud);
+   }
+  });
 
- SU_D(PerlIO_printf(Perl_debug_log, "%p: size=%d pad=%d offset=%d\n",
-                                     ud,    size,   pad,   offset));
+  ixp = &PL_scopestack[cur_scope_ix++];
 
- for (i = cxstack_ix; i > cxix; --i) {
-  PERL_CONTEXT *cx = cxstack + i;
-  switch (CxTYPE(cx)) {
-#if SU_HAS_PERL(5, 11, 0)
-   case CXt_LOOP_FOR:
-   case CXt_LOOP_PLAIN:
-   case CXt_LOOP_LAZYSV:
-   case CXt_LOOP_LAZYIV:
-#else
-   case CXt_LOOP:
 #endif
-    SU_D(PerlIO_printf(Perl_debug_log, "%p: cx %d is loop\n", ud, i));
-    depth += 2;
-    break;
-   default:
-    SU_D(PerlIO_printf(Perl_debug_log, "%p: cx %d is other\n", ud, i));
-    depth++;
-    break;
+
+  if (i == 0) {
+   offset = size;
+  } else {
+   /* we have three constraints to satisfy:
+    * 1) Each adjusted offset must be at least SU_SAVE_DESTRUCTOR_SIZE
+    *    above its unadjusted boundary, so that there is space to inject a
+    *    destructor into the outer scope.
+    * 2) Each adjusted boundary must be at least SU_SAVE_DESTRUCTOR_SIZE
+    *    higher than the previous adjusted boundary, so that a new
+    *    destructor can be added below the Nth adjusted frame boundary,
+    *    but be within the (N-1)th adjusted frame and so be triggered on
+    *    the next scope exit;
+    * 3) If the adjustment needs to be greater than SU_SAVE_DESTRUCTOR_SIZE,
+    *    then it should be greater by an amount of at least the minimum
+    *    pad side, so a destructor and padding can be pushed.
+    */
+   I32 pad;
+   offset = SU_SAVE_DESTRUCTOR_SIZE; /* rule 1 */
+   pad    = (origin[i-1].orig_ix + origin[i-1].offset) + offset
+            - (*ixp + offset);
+   if (pad > 0) { /* rule 2 */
+    if (pad < SU_SAVE_ALLOC_SIZE + 1) /* rule 3 */
+     pad = SU_SAVE_ALLOC_SIZE + 1;
+    offset += pad;
+   }
   }
- }
- SU_D(PerlIO_printf(Perl_debug_log, "%p: going down to depth %d\n", ud, depth));
-
- Newx(origin, depth + 1, I32);
- base = PL_scopestack_ix - depth;
- origin[0] = PL_scopestack[base];
- PL_scopestack[base] += size;
- for (i = 1; i < depth; ++i) {
-  I32 j = i + base;
-  origin[i] = PL_scopestack[j];
-  PL_scopestack[j] += offset;
- }
- origin[depth] = PL_savestack_ix;
 
- SU_UD_ORIGIN(ud) = origin;
- SU_UD_DEPTH(ud)  = depth;
- SU_UD_PAD(ud)    = pad;
+  origin[i].offset  = offset;
+  origin[i].orig_ix = *ixp;
+  *ixp             += offset;
+
+#if SU_HAS_NEW_CXT
+  XSH_D({
+   if (ixp == &PL_scopestack[cur_scope_ix-1])
+    xsh_debug_log(
+     "%p:           ENTER       origin[%d] scope[%d] savestack=%d+%d\n",
+      ud, i, cur_scope_ix, origin[i].orig_ix, origin[i].offset);
+   else
+    xsh_debug_log(
+     "%p:     cx=%-2d %-11s origin[%d] scope[%d] savestack=%d+%d\n",
+      ud, cur_cx_ix-1, SU_CXNAME(cxstack+cur_cx_ix-1),
+      i, cur_scope_ix, origin[i].orig_ix, origin[i].offset);
+  });
+#else
+  XSH_D(xsh_debug_log(
+    "%p:                 ENTER origin[%d] scope[%d] savestack=%d+%d\n",
+     ud, i, cur_scope_ix, origin[i].orig_ix, origin[i].offset));
+#endif
 
- /* Make sure the first destructor fires by pushing enough fake slots on the
-  * stack. */
- if (PL_savestack_ix + SU_SAVE_DESTRUCTOR_SIZE
-                                       <= PL_scopestack[PL_scopestack_ix - 1]) {
-  dMY_CXT;
-  do {
-   SU_D(PerlIO_printf(Perl_debug_log,
-                  "%p: push a fake slot      at scope_ix=%2d  save_ix=%2d\n",
-                   ud,                      PL_scopestack_ix, PL_savestack_ix));
-   SU_SAVE_PLACEHOLDER();
-  } while (PL_savestack_ix + SU_SAVE_DESTRUCTOR_SIZE
-                                        <= PL_scopestack[PL_scopestack_ix - 1]);
  }
- SU_D(PerlIO_printf(Perl_debug_log,
-                  "%p: push first destructor at scope_ix=%2d  save_ix=%2d\n",
-                   ud,                      PL_scopestack_ix, PL_savestack_ix));
- SAVEDESTRUCTOR_X(su_pop, ud);
 
- SU_D({
-  for (i = 0; i <= depth; ++i) {
-   I32 j = PL_scopestack_ix  - i;
-   PerlIO_printf(Perl_debug_log,
-                 "%p: depth=%2d scope_ix=%2d saved_floor=%2d new_floor=%2d\n",
-                  ud,        i, j, origin[depth - i],
-                                   i == 0 ? PL_savestack_ix : PL_scopestack[j]);
-  }
- });
+ assert(i == depth);
 
- return depth;
+ SU_UD_DEPTH(ud)  = depth;
+ SU_UD_ORIGIN(ud) = origin;
+
+ su_ss_push_destructor(ud, depth-1, 1);
 }
 
 /* --- Unwind stack -------------------------------------------------------- */
 
 static void su_unwind(pTHX_ void *ud_) {
- dMY_CXT;
- I32 cxix  = MY_CXT.unwind_storage.cxix;
- I32 items = MY_CXT.unwind_storage.items;
+ dXSH_CXT;
+ I32 cxix  = XSH_CXT.unwind_storage.cxix;
+ I32 items = XSH_CXT.unwind_storage.items;
  I32 mark;
 
  PERL_UNUSED_VAR(ud_);
 
- PL_stack_sp = MY_CXT.unwind_storage.savesp;
-#if SU_HAS_PERL(5, 19, 4)
+ PL_stack_sp = XSH_CXT.unwind_storage.savesp;
+#if XSH_HAS_PERL(5, 19, 4)
  {
   I32 i;
   SV **sp = PL_stack_sp;
@@ -1206,29 +1376,28 @@ static void su_unwind(pTHX_ void *ud_) {
   dounwind(cxix);
 
  mark = PL_markstack[cxstack[cxix].blk_oldmarksp];
- *PL_markstack_ptr = PL_stack_sp - PL_stack_base - items;
+ PUSHMARK(PL_stack_sp - items);
 
- SU_D({
+ XSH_D({
   I32 gimme = GIMME_V;
-  PerlIO_printf(Perl_debug_log,
-                "%p: cx=%d gimme=%s items=%d sp=%d oldmark=%d mark=%d\n",
-                &MY_CXT, cxix,
+  xsh_debug_log("%p: cx=%d gimme=%s items=%d sp=%d oldmark=%d mark=%d\n",
+                &XSH_CXT, cxix,
                 gimme == G_VOID ? "void" : gimme == G_ARRAY ? "list" : "scalar",
                 items, PL_stack_sp - PL_stack_base, *PL_markstack_ptr, mark);
  });
 
- PL_op = (OP *) &(MY_CXT.unwind_storage.return_op);
+ PL_op = (OP *) &(XSH_CXT.unwind_storage.return_op);
  PL_op = PL_op->op_ppaddr(aTHX);
 
  *PL_markstack_ptr = mark;
 
- MY_CXT.unwind_storage.proxy_op.op_next = PL_op;
- PL_op = &(MY_CXT.unwind_storage.proxy_op);
+ XSH_CXT.unwind_storage.proxy_op.op_next = PL_op;
+ PL_op = &(XSH_CXT.unwind_storage.proxy_op);
 }
 
 /* --- Yield --------------------------------------------------------------- */
 
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
 # define SU_RETOP_SUB(C)   ((C)->blk_sub.retop)
 # define SU_RETOP_EVAL(C)  ((C)->blk_eval.retop)
 # define SU_RETOP_LOOP(C)  ((C)->blk_loop.my_op->op_lastop->op_next)
@@ -1240,17 +1409,15 @@ static void su_unwind(pTHX_ void *ud_) {
 #endif
 
 static void su_yield(pTHX_ void *ud_) {
- dMY_CXT;
+ dXSH_CXT;
  PERL_CONTEXT *cx;
  const char   *which = ud_;
- I32 cxix      = MY_CXT.yield_storage.cxix;
- I32 items     = MY_CXT.yield_storage.items;
+ I32 cxix      = XSH_CXT.yield_storage.cxix;
+ I32 items     = XSH_CXT.yield_storage.items;
  opcode  type  = OP_NULL;
  U8      flags = 0;
  OP     *next;
 
- PERL_UNUSED_VAR(ud_);
-
  cx = cxstack + cxix;
  switch (CxTYPE(cx)) {
   case CXt_BLOCK: {
@@ -1258,7 +1425,7 @@ static void su_yield(pTHX_ void *ud_) {
    OP *o = NULL;
    /* Is this actually a given/when block? This may occur only when yield was
     * called with HERE (or nothing) as the context. */
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
    if (cxix > 0) {
     PERL_CONTEXT *prev = cx - 1;
     U8       prev_type = CxTYPE(prev);
@@ -1297,8 +1464,13 @@ static void su_yield(pTHX_ void *ud_) {
      case CXt_EVAL:
       o = SU_RETOP_EVAL(cx2);
       break;
-#if SU_HAS_PERL(5, 11, 0)
+#if XSH_HAS_PERL(5, 11, 0)
+# if XSH_HAS_PERL(5, 23, 8)
+     case CXt_LOOP_ARY:
+     case CXt_LOOP_LIST:
+# else
      case CXt_LOOP_FOR:
+# endif
      case CXt_LOOP_PLAIN:
      case CXt_LOOP_LAZYSV:
      case CXt_LOOP_LAZYIV:
@@ -1338,8 +1510,13 @@ static void su_yield(pTHX_ void *ud_) {
    type = CxTRYBLOCK(cx) ? OP_LEAVETRY : OP_LEAVEEVAL;
    next = SU_RETOP_EVAL(cx);
    break;
-#if SU_HAS_PERL(5, 11, 0)
+#if XSH_HAS_PERL(5, 11, 0)
+# if XSH_HAS_PERL(5, 23, 8)
+  case CXt_LOOP_ARY:
+  case CXt_LOOP_LIST:
+# else
   case CXt_LOOP_FOR:
+# endif
   case CXt_LOOP_PLAIN:
   case CXt_LOOP_LAZYSV:
   case CXt_LOOP_LAZYIV:
@@ -1349,7 +1526,7 @@ static void su_yield(pTHX_ void *ud_) {
    type = OP_LEAVELOOP;
    next = SU_RETOP_LOOP(cx);
    break;
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
   case CXt_GIVEN:
 cxt_given:
    type = OP_LEAVEGIVEN;
@@ -1357,7 +1534,7 @@ cxt_given:
    break;
   case CXt_WHEN:
 cxt_when:
-#if SU_HAS_PERL(5, 15, 1)
+#if XSH_HAS_PERL(5, 15, 1)
    type   = OP_LEAVEWHEN;
 #else
    type   = OP_BREAK;
@@ -1375,8 +1552,8 @@ cxt_when:
    break;
  }
 
- PL_stack_sp = MY_CXT.yield_storage.savesp;
-#if SU_HAS_PERL(5, 19, 4)
+ PL_stack_sp = XSH_CXT.yield_storage.savesp;
+#if XSH_HAS_PERL(5, 19, 4)
  {
   I32 i;
   SV **sp = PL_stack_sp;
@@ -1397,16 +1574,16 @@ cxt_when:
 
  flags |= OP_GIMME_REVERSE(cx->blk_gimme);
 
- MY_CXT.yield_storage.leave_op.op_type   = type;
- MY_CXT.yield_storage.leave_op.op_ppaddr = PL_ppaddr[type];
- MY_CXT.yield_storage.leave_op.op_flags  = flags;
- MY_CXT.yield_storage.leave_op.op_next   = next;
+ XSH_CXT.yield_storage.leave_op.op_type   = type;
+ XSH_CXT.yield_storage.leave_op.op_ppaddr = PL_ppaddr[type];
+ XSH_CXT.yield_storage.leave_op.op_flags  = flags;
+ XSH_CXT.yield_storage.leave_op.op_next   = next;
 
- PL_op = (OP *) &(MY_CXT.yield_storage.leave_op);
+ PL_op = (OP *) &(XSH_CXT.yield_storage.leave_op);
  PL_op = PL_op->op_ppaddr(aTHX);
 
- MY_CXT.yield_storage.proxy_op.op_next = PL_op;
- PL_op = &(MY_CXT.yield_storage.proxy_op);
+ XSH_CXT.yield_storage.proxy_op.op_next = PL_op;
+ PL_op = &(XSH_CXT.yield_storage.proxy_op);
 }
 
 /* --- Uplevel ------------------------------------------------------------- */
@@ -1418,53 +1595,51 @@ static su_uplevel_ud *su_uplevel_storage_new(pTHX_ I32 cxix) {
 #define su_uplevel_storage_new(I) su_uplevel_storage_new(aTHX_ (I))
  su_uplevel_ud *sud;
  UV depth;
- dMY_CXT;
+ dXSH_CXT;
 
- sud = MY_CXT.uplevel_storage.root;
+ sud = XSH_CXT.uplevel_storage.root;
  if (sud) {
-  MY_CXT.uplevel_storage.root = sud->next;
-  MY_CXT.uplevel_storage.count--;
+  XSH_CXT.uplevel_storage.root = sud->next;
+  XSH_CXT.uplevel_storage.count--;
  } else {
   sud = su_uplevel_ud_new();
  }
 
- sud->next = MY_CXT.uplevel_storage.top;
- MY_CXT.uplevel_storage.top = sud;
+ sud->next = XSH_CXT.uplevel_storage.top;
+ XSH_CXT.uplevel_storage.top = sud;
 
  depth = su_uid_depth(cxix);
- su_uid_storage_dup(&sud->tmp_uid_storage, &MY_CXT.uid_storage, depth);
- sud->old_uid_storage = MY_CXT.uid_storage;
- MY_CXT.uid_storage   = sud->tmp_uid_storage;
+ su_uid_storage_dup(&sud->tmp_uid_storage, &XSH_CXT.uid_storage, depth);
+ sud->old_uid_storage = XSH_CXT.uid_storage;
+ XSH_CXT.uid_storage  = sud->tmp_uid_storage;
 
  return sud;
 }
 
-#if SU_HAS_PERL(5, 13, 7)
+#if XSH_HAS_PERL(5, 13, 7)
 
 static void su_uplevel_storage_delete(pTHX_ su_uplevel_ud *sud) {
 #define su_uplevel_storage_delete(S) su_uplevel_storage_delete(aTHX_ (S))
- dMY_CXT;
+ dXSH_CXT;
 
- sud->tmp_uid_storage = MY_CXT.uid_storage;
- MY_CXT.uid_storage   = sud->old_uid_storage;
+ sud->tmp_uid_storage = XSH_CXT.uid_storage;
+ XSH_CXT.uid_storage   = sud->old_uid_storage;
  {
-  su_uid **map;
-  UV  i, alloc;
+  su_uid *map;
+  STRLEN  i, alloc;
   map   = sud->tmp_uid_storage.map;
   alloc = sud->tmp_uid_storage.alloc;
-  for (i = 0; i < alloc; ++i) {
-   if (map[i])
-    map[i]->flags &= SU_UID_ACTIVE;
-  }
+  for (i = 0; i < alloc; ++i)
+   map[i].flags &= ~SU_UID_ACTIVE;
  }
- MY_CXT.uplevel_storage.top = sud->next;
+ XSH_CXT.uplevel_storage.top = sud->next;
 
- if (MY_CXT.uplevel_storage.count >= SU_UPLEVEL_STORAGE_SIZE) {
+ if (XSH_CXT.uplevel_storage.count >= SU_UPLEVEL_STORAGE_SIZE) {
   su_uplevel_ud_delete(sud);
  } else {
-  sud->next = MY_CXT.uplevel_storage.root;
-  MY_CXT.uplevel_storage.root = sud;
-  MY_CXT.uplevel_storage.count++;
+  sud->next = XSH_CXT.uplevel_storage.root;
+  XSH_CXT.uplevel_storage.root = sud;
+  XSH_CXT.uplevel_storage.count++;
  }
 }
 
@@ -1493,7 +1668,7 @@ static int su_uplevel_goto_static(const OP *o) {
  return 0;
 }
 
-#if SU_UPLEVEL_HIJACKS_RUNOPS
+#if !SU_HAS_NEW_CXT && SU_UPLEVEL_HIJACKS_RUNOPS
 
 static int su_uplevel_goto_runops(pTHX) {
 #define su_uplevel_goto_runops() su_uplevel_goto_runops(aTHX)
@@ -1526,9 +1701,9 @@ static int su_uplevel_goto_runops(pTHX) {
 
 done:
    if (argarray) {
-    dMY_CXT;
+    dXSH_CXT;
 
-    if (MY_CXT.uplevel_storage.top->cxix == cxix) {
+    if (XSH_CXT.uplevel_storage.top->cxix == cxix) {
      AV  *args  = GvAV(PL_defgv);
      I32  items = AvFILLp(args);
 
@@ -1541,7 +1716,7 @@ done:
 
   PL_op = op = op->op_ppaddr(aTHX);
 
-#if !SU_HAS_PERL(5, 13, 0)
+#if !XSH_HAS_PERL(5, 13, 0)
   PERL_ASYNC_CHECK();
 #endif
  } while (op);
@@ -1555,7 +1730,53 @@ done:
 
 #define su_at_underscore(C) PadARRAY(PadlistARRAY(CvPADLIST(C))[CvDEPTH(C)])[0]
 
-static void su_uplevel_restore(pTHX_ void *sus_) {
+#if SU_HAS_NEW_CXT
+
+static void su_uplevel_restore_new(pTHX_ void *sus_) {
+ su_uplevel_ud *sud = sus_;
+ PERL_CONTEXT *cx;
+ I32 i;
+ U8 *saved_cxtypes = sud->cxtypes;
+
+ for (i = 0; i < sud->gap; i++) {
+  PERL_CONTEXT *cx = cxstack + sud->cxix + i;
+  XSH_D(xsh_debug_log("su_uplevel_restore: i=%d cxix=%d type %s => %s\n",
+                      i, cx-cxstack, SU_CX_TYPENAME(CxTYPE(cx)),
+                      SU_CX_TYPENAME(saved_cxtypes[i] & CXTYPEMASK)));
+  cx->cx_type = saved_cxtypes[i];
+ }
+ Safefree(saved_cxtypes);
+
+ /* renamed is a copy of callback, but they share the same CvPADLIST.
+  * At this point any calls to renamed should have exited so that its
+  * depth is back to that of of callback. At this point its safe to free
+  * renamed, then undo the extra ref count that was ensuring that callback
+  * remains alive
+  */
+ assert(sud->renamed);
+ assert(sud->callback);
+
+ CvDEPTH(sud->callback)--;
+ assert(CvDEPTH(sud->callback) == CvDEPTH(sud->renamed));
+ if (!CvISXSUB(sud->renamed)) {
+  CvDEPTH(sud->renamed)   = 0;
+  CvPADLIST(sud->renamed) = NULL;
+ }
+ SvREFCNT_dec(sud->renamed);
+ SvREFCNT_dec(sud->callback);
+
+ SU_UPLEVEL_RESTORE(curcop);
+
+ su_uplevel_storage_delete(sud);
+
+ return;
+}
+
+#else
+
+/* 5.23.7 and earlier */
+
+static void su_uplevel_restore_old(pTHX_ void *sus_) {
  su_uplevel_ud *sud = sus_;
  PERL_SI *cur = sud->old_curstackinfo;
  PERL_SI *si  = sud->si;
@@ -1661,7 +1882,7 @@ found_it:
    CvDEPTH(target) = sud->target_depth - levels;
    PL_curstackinfo->si_cxix = i - 1;
 
-#if !SU_HAS_PERL(5, 13, 1)
+#if !XSH_HAS_PERL(5, 13, 1)
    /* Since $@ was maybe localized between the target frame and the uplevel
     * call, we forcefully flush the save stack to get rid of it and then
     * reset $@ to its proper value. Note that the the call to
@@ -1695,28 +1916,30 @@ found_it:
   * pointer to the current context frame across this call. This means that we
   * can't free the temporary context stack we used for the uplevel call right
   * now, or that pointer upwards would point to garbage. */
-#if SU_HAS_PERL(5, 13, 7)
+#if XSH_HAS_PERL(5, 13, 7)
  /* This issue has been fixed in perl with commit 8f89e5a9, which was made
   * public in perl 5.13.7. */
  su_uplevel_storage_delete(sud);
 #else
  /* Otherwise, we just enqueue it back in the global storage list. */
  {
-  dMY_CXT;
+  dXSH_CXT;
 
-  sud->tmp_uid_storage = MY_CXT.uid_storage;
-  MY_CXT.uid_storage   = sud->old_uid_storage;
+  sud->tmp_uid_storage = XSH_CXT.uid_storage;
+  XSH_CXT.uid_storage  = sud->old_uid_storage;
 
-  MY_CXT.uplevel_storage.top  = sud->next;
-  sud->next = MY_CXT.uplevel_storage.root;
-  MY_CXT.uplevel_storage.root = sud;
-  MY_CXT.uplevel_storage.count++;
+  XSH_CXT.uplevel_storage.top  = sud->next;
+  sud->next = XSH_CXT.uplevel_storage.root;
+  XSH_CXT.uplevel_storage.root = sud;
+  XSH_CXT.uplevel_storage.count++;
  }
 #endif
 
  return;
 }
 
+#endif
+
 static CV *su_cv_clone(pTHX_ CV *proto, GV *gv) {
 #define su_cv_clone(P, G) su_cv_clone(aTHX_ (P), (G))
  dVAR;
@@ -1736,14 +1959,14 @@ static CV *su_cv_clone(pTHX_ CV *proto, GV *gv) {
 #endif
 
  CvGV_set(cv, gv);
-#if SU_RELEASE && SU_HAS_PERL_EXACT(5, 21, 4)
+#if SU_RELEASE && XSH_HAS_PERL_EXACT(5, 21, 4)
  CvNAMED_off(cv);
 #endif
  CvSTASH_set(cv, CvSTASH(proto));
  /* Commit 4c74a7df, publicized with perl 5.13.3, began to add backrefs to
   * stashes. CvSTASH_set() started to do it as well with commit c68d95645
   * (which was part of perl 5.13.7). */
-#if SU_HAS_PERL(5, 13, 3) && !SU_HAS_PERL(5, 13, 7)
+#if XSH_HAS_PERL(5, 13, 3) && !XSH_HAS_PERL(5, 13, 7)
  if (CvSTASH(proto))
   Perl_sv_add_backref(aTHX_ CvSTASH(proto), MUTABLE_SV(cv));
 #endif
@@ -1778,8 +2001,129 @@ static CV *su_cv_clone(pTHX_ CV *proto, GV *gv) {
  return cv;
 }
 
-static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
-#define su_uplevel(C, I, A) su_uplevel(aTHX_ (C), (I), (A))
+#if SU_HAS_NEW_CXT
+
+/* this one-shot runops "loop" is designed to be called just before
+ * execution of the first op following an uplevel()'s entersub. It gets a
+ * chance to fix up the args as seen by caller(), before immediately
+ * falling through to the previous runops loop. Note that pp_entersub is
+ * called directly by call_sv() rather than being called from a runops
+ * loop.
+ */
+
+static int su_uplevel_runops_hook_entersub(pTHX) {
+ OP *op = PL_op;
+ dXSH_CXT;
+ su_uplevel_ud *sud = XSH_CXT.uplevel_storage.top;
+
+ /* Create a new array containing a copy of the original sub's call args,
+  * then stick it in PL_curpad[0] of the current running sub so that
+  * thay will be seen by caller().
+  */
+ assert(sud);
+ if (sud->argarray) {
+  I32 fill;
+  AV *av = newAV();
+  AvREAL_off(av);
+  AvREIFY_on(av);
+
+  fill = AvFILLp(sud->argarray);
+  if (fill >= 0) {
+   av_extend(av, fill);
+   Copy(AvARRAY(sud->argarray), AvARRAY(av), fill + 1, SV *);
+   AvFILLp(av) = fill;
+  }
+
+#if !XSH_HAS_PERL(5, 37, 10)
+  /* should be referenced by PL_curpad[0] and *_ */
+  assert(SvREFCNT(PL_curpad[0]) > 1);
+  SvREFCNT_dec(PL_curpad[0]);
+#endif
+
+  PL_curpad[0] = (SV *) av;
+ }
+
+ /* undo the temporary runops hook and fall through to a real runops loop. */
+ assert(sud->old_runops != su_uplevel_runops_hook_entersub);
+ PL_runops = sud->old_runops;
+
+ CALLRUNOPS(aTHX);
+
+ return 0;
+}
+
+static I32 su_uplevel_new(pTHX_ CV *callback, I32 cxix, I32 args) {
+#define su_uplevel_new(CB, CX, A) su_uplevel_new(aTHX_ (CB), (CX), (A))
+ su_uplevel_ud *sud;
+ U8 *saved_cxtypes;
+ I32 i, ret;
+ I32  gimme;
+ CV *base_cv = cxstack[cxix].blk_sub.cv;
+ dSP;
+
+ assert(CxTYPE(&cxstack[cxix]) == CXt_SUB);
+
+ ENTER;
+
+ gimme = GIMME_V;
+
+ /* At this point SP points to the top arg.
+  * Shuffle the args down by one, eliminating the CV slot */
+ Move(SP - args + 1, SP - args, args, SV *);
+ SP--;
+ PUSHMARK(SP - args);
+ PUTBACK;
+
+ sud = su_uplevel_storage_new(cxix);
+
+ sud->cxix     = cxix;
+ sud->callback = (CV *) SvREFCNT_inc_simple(callback);
+ sud->renamed  = NULL;
+ sud->gap      = cxstack_ix - cxix + 1;
+ sud->argarray = NULL;
+
+ Newx(saved_cxtypes, sud->gap, U8);
+ sud->cxtypes = saved_cxtypes;
+
+ SAVEDESTRUCTOR_X(su_uplevel_restore_new, sud);
+ SU_UPLEVEL_SAVE(curcop, cxstack[cxix].blk_oldcop);
+
+/* temporarily change the type of any contexts to NULL, so they're
+ * invisible to caller() etc. */
+ for (i = 0; i < sud->gap; i++) {
+  PERL_CONTEXT *cx = cxstack + cxix + i;
+  saved_cxtypes[i] = cx->cx_type; /* save type and flags */
+  XSH_D(xsh_debug_log("su_uplevel: i=%d cxix=%d type %-11s => %s\n",
+        i, cx-cxstack, SU_CX_TYPENAME(CxTYPE(cx)), SU_CX_TYPENAME(CXt_NULL)));
+  cx->cx_type = (CXt_NULL | CXp_SU_UPLEVEL_NULLED);
+ }
+
+ /* create a copy of the callback with a doctored name (as seen by
+  * caller). It shares the padlist with callback */
+ sud->renamed    = su_cv_clone(callback, CvGV(base_cv));
+ sud->old_runops = PL_runops;
+
+ if (!CvISXSUB(sud->renamed) && CxHASARGS(&cxstack[cxix])) {
+  sud->argarray = (AV *) su_at_underscore(base_cv);
+  assert(PL_runops != su_uplevel_runops_hook_entersub);
+  /* set up a one-shot runops hook so that we can fake up the
+   * args as seen by caller() on return from pp_entersub */
+  PL_runops = su_uplevel_runops_hook_entersub;
+ }
+
+ CvDEPTH(callback)++; /* match what CvDEPTH(sud->renamed) is about to become */
+
+ ret = call_sv((SV *) sud->renamed, gimme);
+
+ LEAVE;
+
+ return ret;
+}
+
+#else
+
+static I32 su_uplevel_old(pTHX_ CV *callback, I32 cxix, I32 args) {
+#define su_uplevel_old(CB, CX, A) su_uplevel_old(aTHX_ (CB), (CX), (A))
  su_uplevel_ud *sud;
  const PERL_CONTEXT *cx = cxstack + cxix;
  PERL_SI *si;
@@ -1807,7 +2151,7 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
  sud->died     = 1;
  sud->callback = NULL;
  sud->renamed  = NULL;
- SAVEDESTRUCTOR_X(su_uplevel_restore, sud);
+ SAVEDESTRUCTOR_X(su_uplevel_restore_old, sud);
 
  si = sud->si;
 
@@ -1822,7 +2166,7 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
   * target context, plus the forthcoming arguments. */
  new_mark = cx->blk_oldsp;
  av_extend(si->si_stack, new_mark + 1 + args + 1);
- Copy(PL_curstack, AvARRAY(si->si_stack), new_mark + 1, SV *);
+ Copy(AvARRAY(PL_curstack), AvARRAY(si->si_stack), new_mark + 1, SV *);
  AvFILLp(si->si_stack) = new_mark;
  SU_POISON(AvARRAY(si->si_stack) + new_mark + 1, args + 1, SV *);
 
@@ -1892,6 +2236,7 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
 
  if ((PL_op = PL_ppaddr[OP_ENTERSUB](aTHX))) {
   PERL_CONTEXT *sub_cx = cxstack + cxstack_ix;
+  AV *argarray = cx->blk_sub.argarray;
 
   /* If pp_entersub() returns a non-null OP, it means that the callback is not
    * an XSUB. */
@@ -1899,7 +2244,7 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
   sud->callback = MUTABLE_CV(SvREFCNT_inc(callback));
   CvDEPTH(callback)++;
 
-  if (CxHASARGS(cx) && cx->blk_sub.argarray) {
+  if (CxHASARGS(cx) && argarray) {
    /* The call to pp_entersub() has saved the current @_ (in XS terms,
     * GvAV(PL_defgv)) in the savearray member, and has created a new argarray
     * with what we put on the stack. But we want to fake up the same arguments
@@ -1908,9 +2253,9 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
    AV *av = newAV();
    AvREAL_off(av);
    AvREIFY_on(av);
-   av_extend(av, AvMAX(cx->blk_sub.argarray));
-   AvFILLp(av) = AvFILLp(cx->blk_sub.argarray);
-   Copy(AvARRAY(cx->blk_sub.argarray), AvARRAY(av), AvFILLp(av) + 1, SV *);
+   av_extend(av, AvMAX(argarray));
+   AvFILLp(av) = AvFILLp(argarray);
+   Copy(AvARRAY(argarray), AvARRAY(av), AvFILLp(av) + 1, SV *);
    sub_cx->blk_sub.argarray = av;
   } else {
    SvREFCNT_inc_simple_void(sub_cx->blk_sub.argarray);
@@ -1957,94 +2302,75 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
  return ret;
 }
 
+#endif
+
 /* --- Unique context ID --------------------------------------------------- */
 
 static su_uid *su_uid_storage_fetch(pTHX_ UV depth) {
 #define su_uid_storage_fetch(D) su_uid_storage_fetch(aTHX_ (D))
- su_uid **map, *uid;
- STRLEN alloc;
- dMY_CXT;
+ su_uid *map;
+ STRLEN  alloc;
+ dXSH_CXT;
 
- map   = MY_CXT.uid_storage.map;
- alloc = MY_CXT.uid_storage.alloc;
+ map   = XSH_CXT.uid_storage.map;
+ alloc = XSH_CXT.uid_storage.alloc;
 
  if (depth >= alloc) {
   STRLEN i;
 
-  Renew(map, depth + 1, su_uid *);
-  for (i = alloc; i <= depth; ++i)
-   map[i] = NULL;
-
-  MY_CXT.uid_storage.map   = map;
-  MY_CXT.uid_storage.alloc = depth + 1;
- }
-
- uid = map[depth];
+  Renew(map, depth + 1, su_uid);
+  for (i = alloc; i <= depth; ++i) {
+   map[i].seq   = 0;
+   map[i].flags = 0;
+  }
 
- if (!uid) {
-  Newx(uid, 1, su_uid);
-  uid->seq   = 0;
-  uid->flags = 0;
-  map[depth] = uid;
+  XSH_CXT.uid_storage.map   = map;
+  XSH_CXT.uid_storage.alloc = depth + 1;
  }
 
- if (depth >= MY_CXT.uid_storage.used)
-  MY_CXT.uid_storage.used = depth + 1;
+ if (depth >= XSH_CXT.uid_storage.used)
+  XSH_CXT.uid_storage.used = depth + 1;
 
- return uid;
+ return map + depth;
 }
 
 static int su_uid_storage_check(pTHX_ UV depth, UV seq) {
 #define su_uid_storage_check(D, S) su_uid_storage_check(aTHX_ (D), (S))
  su_uid *uid;
- dMY_CXT;
+ dXSH_CXT;
 
- if (depth >= MY_CXT.uid_storage.used)
+ if (depth >= XSH_CXT.uid_storage.used)
   return 0;
 
- uid = MY_CXT.uid_storage.map[depth];
+ uid = XSH_CXT.uid_storage.map + depth;
 
- return uid && (uid->seq == seq) && (uid->flags & SU_UID_ACTIVE);
-}
-
-static void su_uid_drop(pTHX_ void *ud_) {
- su_uid *uid = ud_;
-
- uid->flags &= ~SU_UID_ACTIVE;
-}
-
-static void su_uid_bump(pTHX_ void *ud_) {
- su_ud_reap *ud  = ud_;
-
- SAVEDESTRUCTOR_X(su_uid_drop, ud->cb);
-
- SU_UD_FREE(ud);
+ return (uid->seq == seq) && (uid->flags & SU_UID_ACTIVE);
 }
 
 static SV *su_uid_get(pTHX_ I32 cxix) {
 #define su_uid_get(I) su_uid_get(aTHX_ (I))
  su_uid *uid;
- SV *uid_sv;
- UV depth;
+ SV     *uid_sv;
+ UV      depth;
 
  depth = su_uid_depth(cxix);
  uid   = su_uid_storage_fetch(depth);
 
  if (!(uid->flags & SU_UID_ACTIVE)) {
-  su_ud_reap *ud;
+  su_ud_uid *ud;
 
-  uid->seq = su_uid_seq_next(depth);
+  uid->seq    = su_uid_seq_next(depth);
   uid->flags |= SU_UID_ACTIVE;
 
-  Newx(ud, 1, su_ud_reap);
-  SU_UD_ORIGIN(ud)  = NULL;
-  SU_UD_HANDLER(ud) = su_uid_bump;
-  ud->cb = (SV *) uid;
+  Newx(ud, 1, su_ud_uid);
+  SU_UD_TYPE(ud) = SU_UD_TYPE_UID;
+  ud->idx        = depth;
   su_init(ud, cxix, SU_SAVE_DESTRUCTOR_SIZE);
  }
 
  uid_sv = sv_newmortal();
  sv_setpvf(uid_sv, "%"UVuf"-%"UVuf, depth, uid->seq);
+
  return uid_sv;
 }
 
@@ -2120,7 +2446,7 @@ static I32 su_context_skip_db(pTHX_ I32 cxix) {
   PERL_CONTEXT *cx = cxstack + i;
 
   switch (CxTYPE(cx)) {
-#if SU_HAS_PERL(5, 17, 1)
+#if XSH_HAS_PERL(5, 17, 1)
    case CXt_LOOP_PLAIN:
 #endif
    case CXt_BLOCK:
@@ -2143,6 +2469,60 @@ static I32 su_context_skip_db(pTHX_ I32 cxix) {
  return cxix;
 }
 
+#if SU_HAS_NEW_CXT
+
+/* convert a physical context stack index into the logical equivalent:
+ * one that ignores all the context frames hidden by uplevel().
+ * Perl-level functions use logical args (e.g. UP takes an optional logical
+ * value and returns a logical value), while we use and store *real*
+ * values internally.
+ */
+
+static I32 su_context_real2logical(pTHX_ I32 cxix) {
+# define su_context_real2logical(C) su_context_real2logical(aTHX_ (C))
+ PERL_CONTEXT *cx;
+ I32 i, gaps = 0;
+
+ for (i = 0; i <= cxix; i++) {
+  cx = cxstack + i;
+  if (cx->cx_type == (CXt_NULL | CXp_SU_UPLEVEL_NULLED))
+   gaps++;
+ }
+
+ XSH_D(xsh_debug_log("su_context_real2logical: %d => %d\n", cxix, cxix - gaps));
+
+ return cxix - gaps;
+}
+
+/* convert a logical context stack index (one that ignores all the context
+ * frames hidden by uplevel) into the physical equivalent
+ */
+
+static I32 su_context_logical2real(pTHX_ I32 cxix) {
+# define su_context_logical2real(C) su_context_logical2real(aTHX_ (C))
+ PERL_CONTEXT *cx;
+ I32 i, seen = -1;
+
+ for (i = 0; i <= cxstack_ix; i++) {
+  PERL_CONTEXT *cx = cxstack + i;
+  if (cx->cx_type != (CXt_NULL | CXp_SU_UPLEVEL_NULLED))
+   seen++;
+  if (seen >= cxix)
+   break;
+ }
+
+ XSH_D(xsh_debug_log("su_context_logical2real: %d => %d\n", cxix, i));
+
+ if (i > cxstack_ix)
+  i = cxstack_ix;
+
+ return i;
+}
+
+#else
+# define su_context_real2logical(C) (C)
+# define su_context_logical2real(C) (C)
+#endif
 
 static I32 su_context_normalize_up(pTHX_ I32 cxix) {
 #define su_context_normalize_up(C) su_context_normalize_up(aTHX_ (C))
@@ -2156,11 +2536,11 @@ static I32 su_context_normalize_up(pTHX_ I32 cxix) {
   PERL_CONTEXT *prev = cx - 1;
 
   switch (CxTYPE(prev)) {
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
    case CXt_GIVEN:
    case CXt_WHEN:
 #endif
-#if SU_HAS_PERL(5, 11, 0)
+#if XSH_HAS_PERL(5, 11, 0)
    /* That's the only subcategory that can cause an extra BLOCK context */
    case CXt_LOOP_PLAIN:
 #else
@@ -2192,11 +2572,11 @@ static I32 su_context_normalize_down(pTHX_ I32 cxix) {
   PERL_CONTEXT *cx = next - 1;
 
   switch (CxTYPE(cx)) {
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
    case CXt_GIVEN:
    case CXt_WHEN:
 #endif
-#if SU_HAS_PERL(5, 11, 0)
+#if XSH_HAS_PERL(5, 11, 0)
    /* That's the only subcategory that can cause an extra BLOCK context */
    case CXt_LOOP_PLAIN:
 #else
@@ -2227,8 +2607,13 @@ static I32 su_context_gimme(pTHX_ I32 cxix) {
 
   switch (CxTYPE(cx)) {
    /* gimme is always G_ARRAY for loop contexts. */
-#if SU_HAS_PERL(5, 11, 0)
+#if XSH_HAS_PERL(5, 11, 0)
+# if XSH_HAS_PERL(5, 23, 8)
+   case CXt_LOOP_ARY:
+   case CXt_LOOP_LIST:
+# else
    case CXt_LOOP_FOR:
+# endif
    case CXt_LOOP_PLAIN:
    case CXt_LOOP_LAZYSV:
    case CXt_LOOP_LAZYIV:
@@ -2260,90 +2645,61 @@ static I32 su_context_gimme(pTHX_ I32 cxix) {
  return G_VOID;
 }
 
-/* --- Global setup/teardown ----------------------------------------------- */
-
-static VOL U32 su_initialized = 0;
+/* --- Module setup/teardown ----------------------------------------------- */
 
-static void su_global_teardown(pTHX_ void *root) {
- if (!su_initialized)
-  return;
+static void xsh_user_global_setup(pTHX) {
+ HV *stash;
 
-#if SU_MULTIPLICITY
- if (aTHX != root)
-  return;
-#endif
+ MUTEX_INIT(&su_uid_seq_counter_mutex);
 
- SU_LOCK(&su_uid_seq_counter_mutex);
- PerlMemShared_free(su_uid_seq_counter.seqs);
+ XSH_LOCK(&su_uid_seq_counter_mutex);
+ su_uid_seq_counter.seqs = NULL;
  su_uid_seq_counter.size = 0;
- SU_UNLOCK(&su_uid_seq_counter_mutex);
-
- MUTEX_DESTROY(&su_uid_seq_counter_mutex);
+ XSH_UNLOCK(&su_uid_seq_counter_mutex);
 
- su_initialized = 0;
+ stash = gv_stashpv(XSH_PACKAGE, 1);
+ newCONSTSUB(stash, "TOP",           newSViv(0));
+ newCONSTSUB(stash, "SU_THREADSAFE", newSVuv(XSH_THREADSAFE));
 
  return;
 }
 
-XS(XS_Scope__Upper_unwind);
-XS(XS_Scope__Upper_yield);
-XS(XS_Scope__Upper_leave);
-
-#if SU_HAS_PERL(5, 9, 0)
-# define SU_XS_FILE_TYPE const char
-#else
-# define SU_XS_FILE_TYPE char
-#endif
-
-static void su_global_setup(pTHX_ SU_XS_FILE_TYPE *file) {
-#define su_global_setup(F) su_global_setup(aTHX_ (F))
- HV *stash;
-
- if (su_initialized)
-  return;
+static void xsh_user_local_setup(pTHX_ xsh_user_cxt_t *cxt) {
 
- MUTEX_INIT(&su_uid_seq_counter_mutex);
+ /* NewOp() calls calloc() which just zeroes the memory with memset(). */
+ Zero(&(cxt->unwind_storage.return_op), 1, LISTOP);
+ cxt->unwind_storage.return_op.op_type   = OP_RETURN;
+ cxt->unwind_storage.return_op.op_ppaddr = PL_ppaddr[OP_RETURN];
 
- SU_LOCK(&su_uid_seq_counter_mutex);
- su_uid_seq_counter.seqs = NULL;
- su_uid_seq_counter.size = 0;
- SU_UNLOCK(&su_uid_seq_counter_mutex);
+ Zero(&(cxt->unwind_storage.proxy_op), 1, OP);
+ cxt->unwind_storage.proxy_op.op_type   = OP_STUB;
+ cxt->unwind_storage.proxy_op.op_ppaddr = NULL;
 
- stash = gv_stashpv(__PACKAGE__, 1);
- newCONSTSUB(stash, "TOP",           newSViv(0));
- newCONSTSUB(stash, "SU_THREADSAFE", newSVuv(SU_THREADSAFE));
+ Zero(&(cxt->yield_storage.leave_op), 1, UNOP);
+ cxt->yield_storage.leave_op.op_type   = OP_STUB;
+ cxt->yield_storage.leave_op.op_ppaddr = NULL;
 
- newXSproto("Scope::Upper::unwind", XS_Scope__Upper_unwind, file, NULL);
- newXSproto("Scope::Upper::yield",  XS_Scope__Upper_yield,  file, NULL);
- newXSproto("Scope::Upper::leave",  XS_Scope__Upper_leave,  file, NULL);
+ Zero(&(cxt->yield_storage.proxy_op), 1, OP);
+ cxt->yield_storage.proxy_op.op_type   = OP_STUB;
+ cxt->yield_storage.proxy_op.op_ppaddr = NULL;
 
-#if SU_MULTIPLICITY
- call_atexit(su_global_teardown, aTHX);
-#else
- call_atexit(su_global_teardown, NULL);
-#endif
+ cxt->uplevel_storage.top   = NULL;
+ cxt->uplevel_storage.root  = NULL;
+ cxt->uplevel_storage.count = 0;
 
- su_initialized = 1;
+ cxt->uid_storage.map   = NULL;
+ cxt->uid_storage.used  = 0;
+ cxt->uid_storage.alloc = 0;
 
  return;
 }
 
-/* --- Interpreter setup/teardown ------------------------------------------ */
-
-static void su_local_teardown(pTHX_ void *param) {
+static void xsh_user_local_teardown(pTHX_ xsh_user_cxt_t *cxt) {
  su_uplevel_ud *cur;
- su_uid **map;
- dMY_CXT;
 
- map = MY_CXT.uid_storage.map;
- if (map) {
-  STRLEN i;
-  for (i = 0; i < MY_CXT.uid_storage.used; ++i)
-   Safefree(map[i]);
-  Safefree(map);
- }
+ Safefree(cxt->uid_storage.map);
 
- cur = MY_CXT.uplevel_storage.root;
+ cur = cxt->uplevel_storage.root;
  if (cur) {
   su_uplevel_ud *prev;
   do {
@@ -2356,44 +2712,21 @@ static void su_local_teardown(pTHX_ void *param) {
  return;
 }
 
-static void su_local_setup(pTHX) {
-#define su_local_setup() su_local_setup(aTHX)
- MY_CXT_INIT;
-
- MY_CXT.stack_placeholder = NULL;
-
- /* NewOp() calls calloc() which just zeroes the memory with memset(). */
- Zero(&(MY_CXT.unwind_storage.return_op), 1, LISTOP);
- MY_CXT.unwind_storage.return_op.op_type   = OP_RETURN;
- MY_CXT.unwind_storage.return_op.op_ppaddr = PL_ppaddr[OP_RETURN];
-
- Zero(&(MY_CXT.unwind_storage.proxy_op), 1, OP);
- MY_CXT.unwind_storage.proxy_op.op_type   = OP_STUB;
- MY_CXT.unwind_storage.proxy_op.op_ppaddr = NULL;
-
- Zero(&(MY_CXT.yield_storage.leave_op), 1, UNOP);
- MY_CXT.yield_storage.leave_op.op_type   = OP_STUB;
- MY_CXT.yield_storage.leave_op.op_ppaddr = NULL;
-
- Zero(&(MY_CXT.yield_storage.proxy_op), 1, OP);
- MY_CXT.yield_storage.proxy_op.op_type   = OP_STUB;
- MY_CXT.yield_storage.proxy_op.op_ppaddr = NULL;
-
- MY_CXT.uplevel_storage.top   = NULL;
- MY_CXT.uplevel_storage.root  = NULL;
- MY_CXT.uplevel_storage.count = 0;
-
- MY_CXT.uid_storage.map   = NULL;
- MY_CXT.uid_storage.used  = 0;
- MY_CXT.uid_storage.alloc = 0;
+static void xsh_user_global_teardown(pTHX) {
+ XSH_LOCK(&su_uid_seq_counter_mutex);
+ PerlMemShared_free(su_uid_seq_counter.seqs);
+ su_uid_seq_counter.size = 0;
+ XSH_UNLOCK(&su_uid_seq_counter_mutex);
 
- call_atexit(su_local_teardown, NULL);
+ MUTEX_DESTROY(&su_uid_seq_counter_mutex);
 
  return;
 }
 
 /* --- XS ------------------------------------------------------------------ */
 
+/* D is real; B is logical. Returns real. */
+
 #define SU_GET_CONTEXT(A, B, D) \
  STMT_START {                   \
   if (items > A) {              \
@@ -2405,6 +2738,7 @@ static void su_local_setup(pTHX) {
     cxix = 0;                   \
    else if (cxix > cxstack_ix)  \
     goto default_cx;            \
+   cxix = su_context_logical2real(cxix); \
   } else {                      \
 default_cx:                     \
    cxix = (D);                  \
@@ -2424,7 +2758,7 @@ default_cx:                     \
   }                        \
  } STMT_END
 
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
 # define SU_INFO_COUNT 11
 #else
 # define SU_INFO_COUNT 10
@@ -2436,7 +2770,7 @@ XS(XS_Scope__Upper_unwind) {
 #else
  dXSARGS;
 #endif
- dMY_CXT;
+ dXSH_CXT;
  I32 cxix;
 
  PERL_UNUSED_VAR(cv); /* -W */
@@ -2451,12 +2785,12 @@ XS(XS_Scope__Upper_unwind) {
      continue;
    case CXt_EVAL:
    case CXt_FORMAT:
-    MY_CXT.unwind_storage.cxix   = cxix;
-    MY_CXT.unwind_storage.items  = items;
-    MY_CXT.unwind_storage.savesp = PL_stack_sp;
+    XSH_CXT.unwind_storage.cxix   = cxix;
+    XSH_CXT.unwind_storage.items  = items;
+    XSH_CXT.unwind_storage.savesp = PL_stack_sp;
     if (items > 0) {
-     MY_CXT.unwind_storage.items--;
-     MY_CXT.unwind_storage.savesp--;
+     XSH_CXT.unwind_storage.items--;
+     XSH_CXT.unwind_storage.savesp--;
     }
     /* pp_entersub will want to sanitize the stack after returning from there
      * Screw that, we're insane!
@@ -2480,19 +2814,19 @@ XS(XS_Scope__Upper_yield) {
 #else
  dXSARGS;
 #endif
- dMY_CXT;
+ dXSH_CXT;
  I32 cxix;
 
  PERL_UNUSED_VAR(cv); /* -W */
  PERL_UNUSED_VAR(ax); /* -Wall */
 
  SU_GET_CONTEXT(0, items - 1, su_context_here());
- MY_CXT.yield_storage.cxix   = cxix;
- MY_CXT.yield_storage.items  = items;
- MY_CXT.yield_storage.savesp = PL_stack_sp;
+ XSH_CXT.yield_storage.cxix   = cxix;
+ XSH_CXT.yield_storage.items  = items;
+ XSH_CXT.yield_storage.savesp = PL_stack_sp;
  if (items > 0) {
-  MY_CXT.yield_storage.items--;
-  MY_CXT.yield_storage.savesp--;
+  XSH_CXT.yield_storage.items--;
+  XSH_CXT.yield_storage.savesp--;
  }
  /* See XS_Scope__Upper_unwind */
  if (GIMME_V == G_SCALAR)
@@ -2509,18 +2843,20 @@ XS(XS_Scope__Upper_leave) {
 #else
  dXSARGS;
 #endif
- dMY_CXT;
+ dXSH_CXT;
 
  PERL_UNUSED_VAR(cv); /* -W */
  PERL_UNUSED_VAR(ax); /* -Wall */
 
- MY_CXT.yield_storage.cxix   = su_context_here();
- MY_CXT.yield_storage.items  = items;
- MY_CXT.yield_storage.savesp = PL_stack_sp;
+ XSH_CXT.yield_storage.cxix   = su_context_here();
+ XSH_CXT.yield_storage.items  = items;
+ XSH_CXT.yield_storage.savesp = PL_stack_sp;
  /* See XS_Scope__Upper_unwind */
  if (GIMME_V == G_SCALAR)
   PL_stack_sp = PL_stack_base + PL_markstack_ptr[1] + 1;
+
  SAVEDESTRUCTOR_X(su_yield, su_leave_name);
+
  return;
 }
 
@@ -2530,35 +2866,22 @@ PROTOTYPES: ENABLE
 
 BOOT:
 {
- su_global_setup(file);
- su_local_setup();
+ xsh_setup();
+ newXSproto("Scope::Upper::unwind", XS_Scope__Upper_unwind, file, NULL);
+ newXSproto("Scope::Upper::yield",  XS_Scope__Upper_yield,  file, NULL);
+ newXSproto("Scope::Upper::leave",  XS_Scope__Upper_leave,  file, NULL);
 }
 
-#if SU_THREADSAFE
+#if XSH_THREADSAFE
 
 void
 CLONE(...)
 PROTOTYPE: DISABLE
-PREINIT:
- su_uid_storage new_cxt;
 PPCODE:
- {
-  dMY_CXT;
-  new_cxt.map   = NULL;
-  new_cxt.used  = 0;
-  new_cxt.alloc = 0;
-  su_uid_storage_dup(&new_cxt, &MY_CXT.uid_storage, MY_CXT.uid_storage.used);
- }
- {
-  MY_CXT_CLONE;
-  MY_CXT.uplevel_storage.top   = NULL;
-  MY_CXT.uplevel_storage.root  = NULL;
-  MY_CXT.uplevel_storage.count = 0;
-  MY_CXT.uid_storage           = new_cxt;
- }
+ xsh_clone();
  XSRETURN(0);
 
-#endif /* SU_THREADSAFE */
+#endif /* XSH_THREADSAFE */
 
 void
 HERE()
@@ -2566,7 +2889,7 @@ PROTOTYPE:
 PREINIT:
  I32 cxix;
 PPCODE:
- cxix = su_context_here();
+ cxix = su_context_real2logical(su_context_here());
  EXTEND(SP, 1);
  mPUSHi(cxix);
  XSRETURN(1);
@@ -2582,6 +2905,9 @@ PPCODE:
   --cxix;
   cxix = su_context_skip_db(cxix);
   cxix = su_context_normalize_up(cxix);
+  cxix = su_context_real2logical(cxix);
+ } else {
+  warn(su_stack_smash);
  }
  EXTEND(SP, 1);
  mPUSHi(cxix);
@@ -2603,10 +2929,12 @@ PPCODE:
    case CXt_SUB:
     if (PL_DBsub && cx->blk_sub.cv == GvCV(PL_DBsub))
      continue;
+    cxix = su_context_real2logical(cxix);
     mPUSHi(cxix);
     XSRETURN(1);
   }
  }
+ warn(su_no_such_target, "subroutine");
  XSRETURN_UNDEF;
 
 void
@@ -2623,10 +2951,12 @@ PPCODE:
    default:
     continue;
    case CXt_EVAL:
+    cxix = su_context_real2logical(cxix);
     mPUSHi(cxix);
     XSRETURN(1);
   }
  }
+ warn(su_no_such_target, "eval");
  XSRETURN_UNDEF;
 
 void
@@ -2638,11 +2968,14 @@ PPCODE:
  SU_GET_LEVEL(0, 0);
  cxix = su_context_here();
  while (--level >= 0) {
-  if (cxix <= 0)
+  if (cxix <= 0) {
+   warn(su_stack_smash);
    break;
+  }
   --cxix;
   cxix = su_context_skip_db(cxix);
   cxix = su_context_normalize_up(cxix);
+  cxix = su_context_real2logical(cxix);
  }
  EXTEND(SP, 1);
  mPUSHi(cxix);
@@ -2669,7 +3002,10 @@ PPCODE:
   }
  }
 done:
+ if (level >= 0)
+  warn(su_stack_smash);
  EXTEND(SP, 1);
+ cxix = su_context_real2logical(cxix);
  mPUSHi(cxix);
  XSRETURN(1);
 
@@ -2775,7 +3111,7 @@ PPCODE:
   case CXt_EVAL:
    if (CxOLD_OP_TYPE(cx) == OP_ENTEREVAL) {
     /* eval STRING */
-#if SU_HAS_PERL(5, 17, 4)
+#if XSH_HAS_PERL(5, 17, 4)
     PUSHs(newSVpvn_flags(SvPVX(cx->blk_eval.cur_text),
                          SvCUR(cx->blk_eval.cur_text)-2,
                          SvUTF8(cx->blk_eval.cur_text)|SVs_TEMP));
@@ -2802,7 +3138,9 @@ PPCODE:
  /* warnings (9) */
  {
   SV *mask = NULL;
-#if SU_HAS_PERL(5, 9, 4)
+#if XSH_HAS_PERL(5, 37, 6)
+  char *old_warnings = cop->cop_warnings;
+#elif XSH_HAS_PERL(5, 9, 4)
   STRLEN *old_warnings = cop->cop_warnings;
 #else
   SV *old_warnings = cop->cop_warnings;
@@ -2811,20 +3149,20 @@ PPCODE:
    if (PL_dowarn & G_WARN_ON)
     goto context_info_warnings_on;
    else
-#if SU_HAS_PERL(5, 17, 4)
+#if XSH_HAS_PERL(5, 17, 4)
     mask = &PL_sv_undef;
 #else
     goto context_info_warnings_off;
 #endif
   } else if (old_warnings == pWARN_NONE) {
-#if !SU_HAS_PERL(5, 17, 4)
+#if !XSH_HAS_PERL(5, 17, 4)
 context_info_warnings_off:
 #endif
    mask = su_newmortal_pvn(WARN_NONEstring, WARNsize);
   } else if (old_warnings == pWARN_ALL) {
    HV *bits;
 context_info_warnings_on:
-#if SU_HAS_PERL(5, 8, 7)
+#if XSH_HAS_PERL(5, 8, 7)
    bits = get_hv("warnings::Bits", 0);
    if (bits) {
     SV **bits_all = hv_fetchs(bits, "all", FALSE);
@@ -2835,7 +3173,9 @@ context_info_warnings_on:
    if (!mask)
     mask = su_newmortal_pvn(WARN_ALLstring, WARNsize);
   } else {
-#if SU_HAS_PERL(5, 9, 4)
+#if XSH_HAS_PERL(5, 37, 6)
+   mask = su_newmortal_pvn((char *) old_warnings, RCPV_LEN(old_warnings));
+#elif XSH_HAS_PERL(5, 9, 4)
    mask = su_newmortal_pvn((char *) (old_warnings + 1), old_warnings[0]);
 #else
    mask = sv_mortalcopy(old_warnings);
@@ -2843,7 +3183,7 @@ context_info_warnings_on:
   }
   PUSHs(mask);
  }
-#if SU_HAS_PERL(5, 10, 0)
+#if XSH_HAS_PERL(5, 10, 0)
  /* hints hash (10) */
  {
   COPHH *hints_hash = CopHINTHASH_get(cop);
@@ -2867,9 +3207,10 @@ CODE:
  SU_GET_CONTEXT(1, 1, su_context_skip_db(cxstack_ix));
  cxix = su_context_normalize_down(cxix);
  Newx(ud, 1, su_ud_reap);
- SU_UD_ORIGIN(ud)  = NULL;
- SU_UD_HANDLER(ud) = su_reap;
- ud->cb = newSVsv(hook);
+ SU_UD_TYPE(ud) = SU_UD_TYPE_REAP;
+ ud->cb         = (SvROK(hook) && SvTYPE(SvRV(hook)) >= SVt_PVCV)
+                  ? SvRV(hook) : hook;
+ SvREFCNT_inc_simple_void(ud->cb);
  su_init(ud, cxix, SU_SAVE_DESTRUCTOR_SIZE);
 
 void
@@ -2883,8 +3224,7 @@ CODE:
  SU_GET_CONTEXT(2, 2, su_context_skip_db(cxstack_ix));
  cxix = su_context_normalize_down(cxix);
  Newx(ud, 1, su_ud_localize);
- SU_UD_ORIGIN(ud)  = NULL;
- SU_UD_HANDLER(ud) = su_localize;
+ SU_UD_TYPE(ud) = SU_UD_TYPE_LOCALIZE;
  size = su_ud_localize_init(ud, sv, val, NULL);
  su_init(ud, cxix, size);
 
@@ -2901,10 +3241,11 @@ CODE:
  SU_GET_CONTEXT(3, 3, su_context_skip_db(cxstack_ix));
  cxix = su_context_normalize_down(cxix);
  Newx(ud, 1, su_ud_localize);
- SU_UD_ORIGIN(ud)  = NULL;
- SU_UD_HANDLER(ud) = su_localize;
+ /* Initialize SU_UD_ORIGIN(ud) in case SU_UD_LOCALIZE_FREE(ud) needs it */
+ SU_UD_ORIGIN(ud) = NULL;
+ SU_UD_TYPE(ud)   = SU_UD_TYPE_LOCALIZE;
  size = su_ud_localize_init(ud, sv, val, elem);
- if (ud->type != SVt_PVAV && ud->type != SVt_PVHV) {
+ if (SU_UD_PRIVATE(ud) != SVt_PVAV && SU_UD_PRIVATE(ud) != SVt_PVHV) {
   SU_UD_LOCALIZE_FREE(ud);
   croak("Can't localize an element of something that isn't an array or a hash");
  }
@@ -2921,8 +3262,7 @@ CODE:
  SU_GET_CONTEXT(2, 2, su_context_skip_db(cxstack_ix));
  cxix = su_context_normalize_down(cxix);
  Newx(ud, 1, su_ud_localize);
- SU_UD_ORIGIN(ud)  = NULL;
- SU_UD_HANDLER(ud) = su_localize;
+ SU_UD_TYPE(ud) = SU_UD_TYPE_LOCALIZE;
  size = su_ud_localize_init(ud, sv, NULL, elem);
  su_init(ud, cxix, size);
 
@@ -2952,7 +3292,11 @@ PPCODE:
      args = items - 2;
     }
     /* su_uplevel() takes care of extending the stack if needed. */
-    ret = su_uplevel((CV *) code, cxix, args);
+#if SU_HAS_NEW_CXT
+    ret = su_uplevel_new((CV *) code, cxix, args);
+#else
+    ret = su_uplevel_old((CV *) code, cxix, args);
+#endif
     XSRETURN(ret);
    default:
     break;