X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=Upper.xs;h=114161a4879cd4ddfe7f13162360f09ecd0ce89e;hb=70148496e0d2fce5974ae1a869f06b22bd7c119d;hp=f7698d8a3dbb282826e02aa98f528bfe8b225ba0;hpb=5736d907ca8e5e47a4c2c70564014c8b4ec4f1aa;p=perl%2Fmodules%2FScope-Upper.git

diff --git a/Upper.xs b/Upper.xs
index f7698d8..114161a 100644
--- a/Upper.xs
+++ b/Upper.xs
@@ -17,10 +17,7 @@
 /* --- Compatibility ------------------------------------------------------- */
 
 /* perl 5.23.8 onwards has a revamped context system */
-#if XSH_HAS_PERL(5, 23, 8)
-# define SU_HAS_NEW_CXT
-#endif
-
+#define SU_HAS_NEW_CXT XSH_HAS_PERL(5, 23, 8)
 
 #ifndef dVAR
 # define dVAR dNOOP
@@ -203,27 +200,6 @@ static U8 su_op_gimme_reverse(U8 gimme) {
 # define NEGATIVE_INDICES_VAR "NEGATIVE_INDICES"
 #endif
 
-/* CX_ARGARRAY(cx): the AV at pad[0] of the CV associated with CXt_SUB
- * context cx */
-
-#if XSH_HAS_PERL(5, 23, 8)
-# define CX_ARGARRAY(cx) \
-    ((AV*)(AvARRAY(MUTABLE_AV(                     \
-        PadlistARRAY(CvPADLIST(cx->blk_sub.cv))[   \
-            CvDEPTH(cx->blk_sub.cv)]))[0]))
-/* XXX is the new def ok to use in lvalue cxt? Formerly it assigned to
- * blk_sub.argarray, now to pad[0]. Does this matter?
- */
-# define CX_ARGARRAY_set(cx,ary) \
-    (AvARRAY(MUTABLE_AV(                     \
-        PadlistARRAY(CvPADLIST(cx->blk_sub.cv))[   \
-            CvDEPTH(cx->blk_sub.cv)]))[0] = (SV*)(ary))
-#else
-# define CX_ARGARRAY(cx)         (cx->blk_sub.argarray)
-# define CX_ARGARRAY_set(cx,ary) (cx->blk_sub.argarray = (ary))
-#endif
-
-
 /* --- Error messages ------------------------------------------------------ */
 
 static const char su_stack_smash[]    = "Cannot target a scope outside of the current stack";
@@ -374,27 +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;
@@ -407,6 +395,7 @@ 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);
@@ -414,17 +403,21 @@ static su_uplevel_ud *su_uplevel_ud_new(pTHX) {
  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
 
  Safefree(sud->tmp_uid_storage.map);
 
@@ -462,7 +455,6 @@ static void xsh_user_clone(pTHX_ const xsh_user_cxt_t *old_cxt, xsh_user_cxt_t *
  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;
@@ -537,7 +529,6 @@ static void xsh_user_clone(pTHX_ const xsh_user_cxt_t *old_cxt, xsh_user_cxt_t *
 # define SU_SAVE_HELEM_OR_HDELETE_SIZE SU_SAVE_HELEM_SIZE
 #endif
 
-
 #ifndef SvCANEXISTDELETE
 # define SvCANEXISTDELETE(sv) \
   (!SvRMAGICAL(sv)            \
@@ -718,19 +709,18 @@ static void su_save_gvcv(pTHX_ GV *gv) {
 /* --- Actions ------------------------------------------------------------- */
 
 typedef struct {
- I32  orig_ix; /* original savestack_ix */
- I32  offset;  /* how much we bumped this savestack index */
+ 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;
+ U8                 type;
+ U8                 private;
  /* spare */
- I32  depth;
+ 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)
@@ -910,24 +900,26 @@ static void su_localize(pTHX_ void *ud_) {
  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 */
-#ifdef SU_HAS_NEW_CXT
+#if SU_HAS_NEW_CXT
   COP *old_cop = PL_curcop;
-  PL_curcop = CX_CUR()->blk_oldcop;
+  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
-#ifdef SU_HAS_NEW_CXT
-  CX_CUR()->blk_oldcop = PL_curcop;
+
+#if SU_HAS_NEW_CXT
+  CX_CUR()->blk_oldcop = old_cop;
 #endif
  }
 
@@ -997,7 +989,7 @@ static void su_uid_drop(pTHX_ void *ud_) {
 /* --- 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 XSH_HAS_PERL(5, 23, 8)
 static const char *su_block_type[] = {
@@ -1053,9 +1045,13 @@ static const char *su_block_type[] = {
  "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 */
 
@@ -1075,7 +1071,7 @@ static const int su_cxt_enter_count[] = {
 # endif
 };
 
-
+#endif /* XSH_DEBUG */
 
 /* push at least 'size' slots worth of padding onto the savestack */
 
@@ -1090,17 +1086,13 @@ static void su_ss_push_padding(pTHX_ void *ud, I32 size) {
  save_alloc((size - SU_SAVE_ALLOC_SIZE)*sizeof(*PL_savestack), 0);
 }
 
-
 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) {
  su_ud_origin_elem *origin = SU_UD_ORIGIN(ud);
- I32 pad;
 
  assert(first || origin[depth+1].orig_ix == PL_savestack_ix);
  su_ss_push_padding(aTHX_ ud,
@@ -1113,7 +1105,6 @@ static void su_ss_push_destructor(pTHX_ void *ud, I32 depth, bool first) {
         PL_savestack_ix <= origin[depth+1].orig_ix +  origin[depth+1].offset);
 }
 
-
 /* this is called during each leave_scope() via SAVEDESTRUCTOR_X */
 
 static void su_pop(pTHX_ void *ud) {
@@ -1174,12 +1165,11 @@ static void su_pop(pTHX_ void *ud) {
  XSH_D(su_debug_log("%p:     end pop: ss_ix=%d\n", ud, PL_savestack_ix));
 }
 
-
 /* --- Initialize the stack and the action userdata ------------------------ */
 
 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, base;
+ I32 i, depth;
  su_ud_origin_elem *origin;
  I32 cur_cx_ix;
  I32 cur_scope_ix;
@@ -1187,7 +1177,7 @@ static void su_init(pTHX_ void *ud, I32 cxix, I32 size) {
  XSH_D(su_debug_log("%p: ### su_init(cxix=%d, size=%d)\n", ud, cxix, size));
 
  depth = PL_scopestack_ix - cxstack[cxix].blk_oldscopesp;
-#ifdef SU_HAS_NEW_CXT
+#if SU_HAS_NEW_CXT
  depth += (cxstack_ix - cxix); /* each context frame holds 1 scope */
 #endif
  XSH_D(su_debug_log(
@@ -1232,14 +1222,14 @@ static void su_init(pTHX_ void *ud, I32 cxix, I32 size) {
   *
   * 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. 
+  * including) that context.
   */
 
  Newx(origin, depth, su_ud_origin_elem);
 
  cur_cx_ix  = cxix;
  cur_scope_ix = cxstack[cxix].blk_oldscopesp;
-#ifdef SU_HAS_NEW_CXT
+#if SU_HAS_NEW_CXT
  XSH_D(su_debug_log("%p:     cx=%-2d %-11s\n",
       ud, cur_cx_ix, SU_CXNAME(cxstack+cur_cx_ix)));
  cur_cx_ix++;
@@ -1249,7 +1239,7 @@ static void su_init(pTHX_ void *ud, I32 cxix, I32 size) {
   I32 *ixp;
   I32 offset;
 
-#ifdef SU_HAS_NEW_CXT
+#if SU_HAS_NEW_CXT
 
   if (   cur_cx_ix <= cxstack_ix
       && cur_scope_ix == cxstack[cur_cx_ix].blk_oldscopesp
@@ -1307,7 +1297,7 @@ static void su_init(pTHX_ void *ud, I32 cxix, I32 size) {
   origin[i].orig_ix = *ixp;
   *ixp += offset;
 
-#ifdef SU_HAS_NEW_CXT
+#if SU_HAS_NEW_CXT
   XSH_D({
    if (ixp == &PL_scopestack[cur_scope_ix-1])
     su_debug_log(
@@ -1335,7 +1325,6 @@ static void su_init(pTHX_ void *ud, I32 cxix, I32 size) {
  su_ss_push_destructor(aTHX_ ud, depth-1, 1);
 }
 
-
 /* --- Unwind stack -------------------------------------------------------- */
 
 static void su_unwind(pTHX_ void *ud_) {
@@ -1655,7 +1644,7 @@ 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)
@@ -1674,7 +1663,7 @@ static int su_uplevel_goto_runops(pTHX) {
     switch (CxTYPE(cx)) {
      case CXt_SUB:
       if (CxHASARGS(cx)) {
-       argarray = CX_ARGARRAY(cx);
+       argarray = cx->blk_sub.argarray;
        goto done;
       }
       break;
@@ -1717,7 +1706,53 @@ 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(su_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;
@@ -1749,8 +1784,8 @@ static void su_uplevel_restore(pTHX_ void *sus_) {
    * reached without a goto() happening, and the old argarray member is
    * actually our fake argarray. Destroy it properly in that case. */
   if (cx->blk_sub.cv == sud->renamed) {
-   SvREFCNT_dec(CX_ARGARRAY(cx));
-   CX_ARGARRAY_set(cx, argarray);
+   SvREFCNT_dec(cx->blk_sub.argarray);
+   cx->blk_sub.argarray = argarray;
   }
 
   CvDEPTH(sud->callback)--;
@@ -1879,6 +1914,8 @@ found_it:
  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;
@@ -1940,8 +1977,118 @@ 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) {
+  AV *av = newAV();
+  AvREAL_off(av);
+  AvREIFY_on(av);
+  av_extend(av, AvMAX(sud->argarray));
+  AvFILLp(av) = AvFILLp(sud->argarray);
+  Copy(AvARRAY(sud->argarray), AvARRAY(av), AvFILLp(av) + 1, SV *);
+
+  /* should be referenced by PL_curpad[0] and *_ */
+  assert(SvREFCNT(PL_curpad[0]) > 1);
+  SvREFCNT_dec(PL_curpad[0]);
+
+  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) {
+ 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(su_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) {
  su_uplevel_ud *sud;
  const PERL_CONTEXT *cx = cxstack + cxix;
  PERL_SI *si;
@@ -1969,7 +2116,7 @@ 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;
 
@@ -2054,7 +2201,7 @@ 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_ARGARRAY(cx);
+  AV *argarray = cx->blk_sub.argarray;
 
   /* If pp_entersub() returns a non-null OP, it means that the callback is not
    * an XSUB. */
@@ -2074,9 +2221,9 @@ static I32 su_uplevel(pTHX_ CV *callback, I32 cxix, I32 args) {
    av_extend(av, AvMAX(argarray));
    AvFILLp(av) = AvFILLp(argarray);
    Copy(AvARRAY(argarray), AvARRAY(av), AvFILLp(av) + 1, SV *);
-   CX_ARGARRAY_set(sub_cx, av);
+   sub_cx->blk_sub.argarray = av;
   } else {
-   SvREFCNT_inc_simple_void(CX_ARGARRAY(sub_cx));
+   SvREFCNT_inc_simple_void(sub_cx->blk_sub.argarray);
   }
 
   if (su_uplevel_goto_static(CvROOT(renamed))) {
@@ -2120,6 +2267,8 @@ 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) {
@@ -2285,6 +2434,55 @@ 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(su_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(su_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))
@@ -2487,6 +2685,8 @@ static void xsh_user_global_teardown(pTHX) {
 
 /* --- XS ------------------------------------------------------------------ */
 
+/* D is real; B is logical. Returns real. */
+
 #define SU_GET_CONTEXT(A, B, D) \
  STMT_START {                   \
   if (items > A) {              \
@@ -2498,6 +2698,7 @@ static void xsh_user_global_teardown(pTHX) {
     cxix = 0;                   \
    else if (cxix > cxstack_ix)  \
     goto default_cx;            \
+   cxix = su_context_logical2real(cxix); \
   } else {                      \
 default_cx:                     \
    cxix = (D);                  \
@@ -2646,7 +2847,7 @@ PROTOTYPE:
 PREINIT:
  I32 cxix;
 PPCODE:
- cxix = su_context_here();
+ cxix = su_context_real2logical(su_context_here());
  EXTEND(SP, 1);
  mPUSHi(cxix);
  XSRETURN(1);
@@ -2662,6 +2863,7 @@ PPCODE:
   --cxix;
   cxix = su_context_skip_db(cxix);
   cxix = su_context_normalize_up(cxix);
+  cxix = su_context_real2logical(cxix);
  } else {
   warn(su_stack_smash);
  }
@@ -2685,6 +2887,7 @@ PPCODE:
    case CXt_SUB:
     if (PL_DBsub && cx->blk_sub.cv == GvCV(PL_DBsub))
      continue;
+    cxix = su_context_real2logical(cxix);
     mPUSHi(cxix);
     XSRETURN(1);
   }
@@ -2706,6 +2909,7 @@ PPCODE:
    default:
     continue;
    case CXt_EVAL:
+    cxix = su_context_real2logical(cxix);
     mPUSHi(cxix);
     XSRETURN(1);
   }
@@ -2729,6 +2933,7 @@ PPCODE:
   --cxix;
   cxix = su_context_skip_db(cxix);
   cxix = su_context_normalize_up(cxix);
+  cxix = su_context_real2logical(cxix);
  }
  EXTEND(SP, 1);
  mPUSHi(cxix);
@@ -2758,6 +2963,7 @@ done:
  if (level >= 0)
   warn(su_stack_smash);
  EXTEND(SP, 1);
+ cxix = su_context_real2logical(cxix);
  mPUSHi(cxix);
  XSRETURN(1);
 
@@ -3040,7 +3246,11 @@ 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(aTHX_ (CV *) code, cxix, args);
+#else
+    ret = su_uplevel_old(aTHX_ (CV *) code, cxix, args);
+#endif
     XSRETURN(ret);
    default:
     break;