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pp_return: avoid potential CX stack realloc prob
[perl5.git] / cop.h
diff --git a/cop.h b/cop.h
index 37980f0..525f546 100644 (file)
--- a/cop.h
+++ b/cop.h
@@ -7,7 +7,7 @@
  *    License or the Artistic License, as specified in the README file.
  *
  * Control ops (cops) are one of the two ops OP_NEXTSTATE and OP_DBSTATE,
- * that (loosely speaking) are separate statements.
+ * that (loosely speaking) are statement separators.
  * They hold information important for lexical state and error reporting.
  * At run time, PL_curcop is set to point to the most recently executed cop,
  * and thus can be used to determine our current state.
@@ -34,6 +34,7 @@ struct jmpenv {
     Sigjmp_buf         je_buf;         /* uninit if je_prev is NULL */
     int                        je_ret;         /* last exception thrown */
     bool               je_mustcatch;   /* need to call longjmp()? */
+    U16                 je_old_delaymagic; /* saved PL_delaymagic */
 };
 
 typedef struct jmpenv JMPENV;
@@ -55,6 +56,7 @@ typedef struct jmpenv JMPENV;
        PL_start_env.je_prev = NULL;            \
        PL_start_env.je_ret = -1;               \
        PL_start_env.je_mustcatch = TRUE;       \
+       PL_start_env.je_old_delaymagic = 0;     \
     } STMT_END
 
 /*
@@ -103,6 +105,7 @@ typedef struct jmpenv JMPENV;
        cur_env.je_ret = PerlProc_setjmp(cur_env.je_buf, SCOPE_SAVES_SIGNAL_MASK);              \
        PL_top_env = &cur_env;                                          \
        cur_env.je_mustcatch = FALSE;                                   \
+       cur_env.je_old_delaymagic = PL_delaymagic;                      \
        (v) = cur_env.je_ret;                                           \
     } STMT_END
 
@@ -114,6 +117,7 @@ typedef struct jmpenv JMPENV;
            Perl_deb(aTHX_ "JUMPENV_POP level=%d at %s:%d\n",           \
                         i, __FILE__, __LINE__);})                      \
        assert(PL_top_env == &cur_env);                                 \
+       PL_delaymagic = cur_env.je_old_delaymagic;                      \
        PL_top_env = cur_env.je_prev;                                   \
     } STMT_END
 
@@ -154,10 +158,10 @@ typedef struct refcounted_he COPHH;
 /*
 =for apidoc Amx|SV *|cophh_fetch_pvn|const COPHH *cophh|const char *keypv|STRLEN keylen|U32 hash|U32 flags
 
-Look up the entry in the cop hints hash I<cophh> with the key specified by
-I<keypv> and I<keylen>.  If I<flags> has the C<COPHH_KEY_UTF8> bit set,
+Look up the entry in the cop hints hash C<cophh> with the key specified by
+C<keypv> and C<keylen>.  If C<flags> has the C<COPHH_KEY_UTF8> bit set,
 the key octets are interpreted as UTF-8, otherwise they are interpreted
-as Latin-1.  I<hash> is a precomputed hash of the key string, or zero if
+as Latin-1.  C<hash> is a precomputed hash of the key string, or zero if
 it has not been precomputed.  Returns a mortal scalar copy of the value
 associated with the key, or C<&PL_sv_placeholder> if there is no value
 associated with the key.
@@ -208,7 +212,7 @@ string/length pair.
 =for apidoc Amx|HV *|cophh_2hv|const COPHH *cophh|U32 flags
 
 Generates and returns a standard Perl hash representing the full set of
-key/value pairs in the cop hints hash I<cophh>.  I<flags> is currently
+key/value pairs in the cop hints hash C<cophh>.  C<flags> is currently
 unused and must be zero.
 
 =cut
@@ -220,7 +224,7 @@ unused and must be zero.
 /*
 =for apidoc Amx|COPHH *|cophh_copy|COPHH *cophh
 
-Make and return a complete copy of the cop hints hash I<cophh>.
+Make and return a complete copy of the cop hints hash C<cophh>.
 
 =cut
 */
@@ -230,7 +234,7 @@ Make and return a complete copy of the cop hints hash I<cophh>.
 /*
 =for apidoc Amx|void|cophh_free|COPHH *cophh
 
-Discard the cop hints hash I<cophh>, freeing all resources associated
+Discard the cop hints hash C<cophh>, freeing all resources associated
 with it.
 
 =cut
@@ -251,18 +255,18 @@ Generate and return a fresh cop hints hash containing no entries.
 /*
 =for apidoc Amx|COPHH *|cophh_store_pvn|COPHH *cophh|const char *keypv|STRLEN keylen|U32 hash|SV *value|U32 flags
 
-Stores a value, associated with a key, in the cop hints hash I<cophh>,
+Stores a value, associated with a key, in the cop hints hash C<cophh>,
 and returns the modified hash.  The returned hash pointer is in general
 not the same as the hash pointer that was passed in.  The input hash is
 consumed by the function, and the pointer to it must not be subsequently
 used.  Use L</cophh_copy> if you need both hashes.
 
-The key is specified by I<keypv> and I<keylen>.  If I<flags> has the
+The key is specified by C<keypv> and C<keylen>.  If C<flags> has the
 C<COPHH_KEY_UTF8> bit set, the key octets are interpreted as UTF-8,
-otherwise they are interpreted as Latin-1.  I<hash> is a precomputed
+otherwise they are interpreted as Latin-1.  C<hash> is a precomputed
 hash of the key string, or zero if it has not been precomputed.
 
-I<value> is the scalar value to store for this key.  I<value> is copied
+C<value> is the scalar value to store for this key.  C<value> is copied
 by this function, which thus does not take ownership of any reference
 to it, and later changes to the scalar will not be reflected in the
 value visible in the cop hints hash.  Complex types of scalar will not
@@ -313,15 +317,15 @@ string/length pair.
 /*
 =for apidoc Amx|COPHH *|cophh_delete_pvn|COPHH *cophh|const char *keypv|STRLEN keylen|U32 hash|U32 flags
 
-Delete a key and its associated value from the cop hints hash I<cophh>,
+Delete a key and its associated value from the cop hints hash C<cophh>,
 and returns the modified hash.  The returned hash pointer is in general
 not the same as the hash pointer that was passed in.  The input hash is
 consumed by the function, and the pointer to it must not be subsequently
 used.  Use L</cophh_copy> if you need both hashes.
 
-The key is specified by I<keypv> and I<keylen>.  If I<flags> has the
+The key is specified by C<keypv> and C<keylen>.  If C<flags> has the
 C<COPHH_KEY_UTF8> bit set, the key octets are interpreted as UTF-8,
-otherwise they are interpreted as Latin-1.  I<hash> is a precomputed
+otherwise they are interpreted as Latin-1.  C<hash> is a precomputed
 hash of the key string, or zero if it has not been precomputed.
 
 =cut
@@ -457,10 +461,10 @@ struct cop {
 /*
 =for apidoc Am|SV *|cop_hints_fetch_pvn|const COP *cop|const char *keypv|STRLEN keylen|U32 hash|U32 flags
 
-Look up the hint entry in the cop I<cop> with the key specified by
-I<keypv> and I<keylen>.  If I<flags> has the C<COPHH_KEY_UTF8> bit set,
+Look up the hint entry in the cop C<cop> with the key specified by
+C<keypv> and C<keylen>.  If C<flags> has the C<COPHH_KEY_UTF8> bit set,
 the key octets are interpreted as UTF-8, otherwise they are interpreted
-as Latin-1.  I<hash> is a precomputed hash of the key string, or zero if
+as Latin-1.  C<hash> is a precomputed hash of the key string, or zero if
 it has not been precomputed.  Returns a mortal scalar copy of the value
 associated with the key, or C<&PL_sv_placeholder> if there is no value
 associated with the key.
@@ -511,7 +515,7 @@ string/length pair.
 =for apidoc Am|HV *|cop_hints_2hv|const COP *cop|U32 flags
 
 Generates and returns a standard Perl hash representing the full set of
-hint entries in the cop I<cop>.  I<flags> is currently unused and must
+hint entries in the cop C<cop>.  C<flags> is currently unused and must
 be zero.
 
 =cut
@@ -547,12 +551,11 @@ be zero.
 struct block_sub {
     OP *       retop;  /* op to execute on exit from sub */
     /* Above here is the same for sub, format and eval.  */
+    PAD                *prevcomppad; /* the caller's PL_comppad */
     CV *       cv;
     /* Above here is the same for sub and format.  */
-    AV *       savearray;
-    AV *       argarray;
     I32                olddepth;
-    PAD                *oldcomppad;
+    AV         *savearray;
 };
 
 
@@ -560,15 +563,33 @@ struct block_sub {
 struct block_format {
     OP *       retop;  /* op to execute on exit from sub */
     /* Above here is the same for sub, format and eval.  */
+    PAD                *prevcomppad; /* the caller's PL_comppad */
     CV *       cv;
     /* Above here is the same for sub and format.  */
     GV *       gv;
     GV *       dfoutgv;
 };
 
+/* free all savestack items back to the watermark of the specified context */
+
+#define CX_LEAVE_SCOPE(cx) LEAVE_SCOPE(cx->cx_old_savestack_ix)
+
+#ifdef DEBUGGING
+/* on debugging builds, poison cx afterwards so we know no code
+ * uses it - because after doing cxstack_ix--, any ties, exceptions etc
+ * may overwrite the current stack frame */
+#  define CX_POP(cx)                                                   \
+        assert(&cxstack[cxstack_ix] == cx);                            \
+        cxstack_ix--;                                                  \
+        cx = NULL;
+#else
+#  define CX_POP(cx) cxstack_ix--;
+#endif
+
+
 /* base for the next two macros. Don't use directly.
- * Note that the refcnt of the cv is incremented twice;  The CX one is
- * decremented by LEAVESUB, the other by LEAVE. */
+ * The context frame holds a reference to the CV so that it can't be
+ * freed while we're executing it */
 
 #define PUSHSUB_BASE(cx)                                               \
        ENTRY_PROBE(CvNAMED(cv)                                         \
@@ -580,13 +601,10 @@ struct block_format {
                                                                        \
        cx->blk_sub.cv = cv;                                            \
        cx->blk_sub.olddepth = CvDEPTH(cv);                             \
+       cx->blk_sub.prevcomppad = PL_comppad;                           \
        cx->cx_type |= (hasargs) ? CXp_HASARGS : 0;                     \
        cx->blk_sub.retop = NULL;                                       \
-       if (!CvDEPTH(cv)) {                                             \
-           SvREFCNT_inc_simple_void_NN(cv);                            \
-           SvREFCNT_inc_simple_void_NN(cv);                            \
-           SAVEFREESV(cv);                                             \
-       }
+        SvREFCNT_inc_simple_void_NN(cv);
 
 #define PUSHSUB_GET_LVALUE_MASK(func) \
        /* If the context is indeterminate, then only the lvalue */     \
@@ -617,14 +635,19 @@ struct block_format {
        cx->blk_format.gv = gv;                                         \
        cx->blk_format.retop = (retop);                                 \
        cx->blk_format.dfoutgv = PL_defoutgv;                           \
-       if (!CvDEPTH(cv)) SvREFCNT_inc_simple_void_NN(cv);              \
+       cx->blk_format.prevcomppad = PL_comppad;                        \
+       cx->blk_u16 = 0;                                                \
+        cx->cx_old_savestack_ix = PL_savestack_ix;                      \
+       SvREFCNT_inc_simple_void_NN(cv);                                \
        CvDEPTH(cv)++;                                                  \
        SvREFCNT_inc_void(cx->blk_format.dfoutgv)
 
+/* Restore old @_ */
 #define POP_SAVEARRAY()                                                \
     STMT_START {                                                       \
-       SvREFCNT_dec(GvAV(PL_defgv));                                   \
+        AV *av = GvAV(PL_defgv);                                        \
        GvAV(PL_defgv) = cx->blk_sub.savearray;                         \
+        SvREFCNT_dec(av);                                              \
     } STMT_END
 
 /* junk in @_ spells trouble when cloning CVs and in pp_caller(), so don't
@@ -636,9 +659,37 @@ struct block_format {
        AvFILLp(ary) = -1;                                              \
     } STMT_END
 
-#define POPSUB(cx,sv)                                                  \
+
+/* subsets of POPSUB */
+
+#define POPSUB_COMMON(cx) \
+    PL_comppad = cx->blk_sub.prevcomppad;                               \
+    PL_curpad = LIKELY(PL_comppad) ? AvARRAY(PL_comppad) : NULL;        \
+    CvDEPTH((const CV*)cx->blk_sub.cv) = cx->blk_sub.olddepth;          \
+    SvREFCNT_dec_NN(cx->blk_sub.cv);
+
+/* handle the @_ part of leaving a sub */
+
+#define POPSUB_ARGS(cx) \
     STMT_START {                                                       \
-       const I32 olddepth = cx->blk_sub.olddepth;                      \
+        AV *av;                                                         \
+        assert(AvARRAY(MUTABLE_AV(                                      \
+            PadlistARRAY(CvPADLIST(cx->blk_sub.cv))[                    \
+                    CvDEPTH(cx->blk_sub.cv)])) == PL_curpad);           \
+        POP_SAVEARRAY();                                               \
+        /* abandon @_ if it got reified */                             \
+        av = MUTABLE_AV(PAD_SVl(0));                                    \
+        if (UNLIKELY(AvREAL(av)))                                      \
+            clear_defarray(av, 0);                                      \
+        else {                                                         \
+            CLEAR_ARGARRAY(av);                                                \
+        }                                                              \
+    } STMT_END
+
+#define POPSUB(cx)                                                     \
+    STMT_START {                                                       \
+        if (!(cx->blk_u16 & CxPOPSUB_DONE)) {                           \
+        cx->blk_u16 |= CxPOPSUB_DONE;                                   \
        RETURN_PROBE(CvNAMED(cx->blk_sub.cv)                            \
                        ? HEK_KEY(CvNAME_HEK(cx->blk_sub.cv))           \
                        : GvENAME(CvGV(cx->blk_sub.cv)),                \
@@ -647,40 +698,25 @@ struct block_format {
                CopSTASHPV((COP*)CvSTART((const CV*)cx->blk_sub.cv)));  \
                                                                        \
        if (CxHASARGS(cx)) {                                            \
-           POP_SAVEARRAY();                                            \
-           /* abandon @_ if it got reified */                          \
-           if (AvREAL(cx->blk_sub.argarray)) {                         \
-               const SSize_t fill = AvFILLp(cx->blk_sub.argarray);     \
-               SvREFCNT_dec_NN(cx->blk_sub.argarray);                  \
-               cx->blk_sub.argarray = newAV();                         \
-               av_extend(cx->blk_sub.argarray, fill);                  \
-               AvREIFY_only(cx->blk_sub.argarray);                     \
-               CX_CURPAD_SV(cx->blk_sub, 0) = MUTABLE_SV(cx->blk_sub.argarray); \
-           }                                                           \
-           else {                                                      \
-               CLEAR_ARGARRAY(cx->blk_sub.argarray);                   \
-           }                                                           \
+            POPSUB_ARGS(cx);                                            \
        }                                                               \
-       sv = MUTABLE_SV(cx->blk_sub.cv);                                \
-       LEAVE_SCOPE(PL_scopestack[cx->blk_oldscopesp-1]);               \
-       if (sv && (CvDEPTH((const CV*)sv) = olddepth))                  \
-           sv = NULL;                                          \
-    } STMT_END
-
-#define LEAVESUB(sv)                                                   \
-    STMT_START {                                                       \
-       SvREFCNT_dec(sv);                                               \
+        }                                                               \
+        POPSUB_COMMON(cx);                                              \
     } STMT_END
 
 #define POPFORMAT(cx)                                                  \
     STMT_START {                                                       \
+        if (!(cx->blk_u16 & CxPOPSUB_DONE)) {                           \
        CV * const cv = cx->blk_format.cv;                              \
        GV * const dfuot = cx->blk_format.dfoutgv;                      \
+        cx->blk_u16 |= CxPOPSUB_DONE;                                   \
        setdefout(dfuot);                                               \
-       LEAVE_SCOPE(PL_scopestack[cx->blk_oldscopesp-1]);               \
-       if (!--CvDEPTH(cv))                                             \
-           SvREFCNT_dec_NN(cx->blk_format.cv);                         \
+        PL_comppad = cx->blk_format.prevcomppad;                        \
+        PL_curpad = LIKELY(PL_comppad) ? AvARRAY(PL_comppad) : NULL;    \
+       --CvDEPTH(cv);                                                  \
+       SvREFCNT_dec_NN(cx->blk_format.cv);                             \
        SvREFCNT_dec_NN(dfuot);                                         \
+        }                                                               \
     } STMT_END
 
 /* eval context */
@@ -717,7 +753,6 @@ struct block_eval {
 #define POPEVAL(cx)                                                    \
     STMT_START {                                                       \
        PL_in_eval = CxOLD_IN_EVAL(cx);                                 \
-       optype = CxOLD_OP_TYPE(cx);                                     \
        PL_eval_root = cx->blk_eval.old_eval_root;                      \
        if (cx->blk_eval.cur_text && SvSCREAM(cx->blk_eval.cur_text))   \
            SvREFCNT_dec_NN(cx->blk_eval.cur_text);                     \
@@ -730,10 +765,10 @@ struct block_loop {
     I32                resetsp;
     LOOP *     my_op;  /* My op, that contains redo, next and last ops.  */
     union {    /* different ways of locating the iteration variable */
-       SV      **svp;
-       GV      *gv;
-       PAD     *oldcomppad; /* only used in ITHREADS */
+       SV      **svp; /* for lexicals: address of pad slot */
+       GV      *gv;   /* for package vars */
     } itervar_u;
+    SV          *itersave; /* the original iteration var */
     union {
        struct { /* valid if type is LOOP_FOR or LOOP_PLAIN (but {NULL,0})*/
            AV * ary; /* use the stack if this is NULL */
@@ -748,59 +783,99 @@ struct block_loop {
            SV * end; /* maxiumum value (or minimum in reverse) */
        } lazysv;
     } state_u;
-};
-
 #ifdef USE_ITHREADS
-#  define CxITERVAR_PADSV(c) \
-       &CX_CURPAD_SV( (c)->blk_loop.itervar_u, (c)->blk_loop.my_op->op_targ)
-#else
-#  define CxITERVAR_PADSV(c) ((c)->blk_loop.itervar_u.svp)
+    PAD *oldcomppad; /* needed to map itervar_u.svp during thread clone */
 #endif
+};
 
-#define CxITERVAR(c)                                                   \
-       ((c)->blk_loop.itervar_u.oldcomppad                             \
-        ? (CxPADLOOP(c)                                                \
-           ? CxITERVAR_PADSV(c)                                        \
-           : &GvSV((c)->blk_loop.itervar_u.gv))                        \
-        : (SV**)NULL)
+#define CxITERVAR(c)                                    \
+        (CxPADLOOP(c)                                   \
+            ? (c)->blk_loop.itervar_u.svp               \
+            : ((c)->cx_type & CXp_FOR_GV)               \
+                ? &GvSV((c)->blk_loop.itervar_u.gv)     \
+                : (SV **)&(c)->blk_loop.itervar_u.gv)
 
 #define CxLABEL(c)     (0 + CopLABEL((c)->blk_oldcop))
 #define CxLABEL_len(c,len)     (0 + CopLABEL_len((c)->blk_oldcop, len))
 #define CxLABEL_len_flags(c,len,flags) (0 + CopLABEL_len_flags((c)->blk_oldcop, len, flags))
 #define CxHASARGS(c)   (((c)->cx_type & CXp_HASARGS) == CXp_HASARGS)
-#define CxLVAL(c)      (0 + (c)->blk_u16)
+#define CxLVAL(c)      (0 + ((c)->blk_u16 & 0xff))
+/* POPSUB has already been performed on this context frame */
+#define CxPOPSUB_DONE 0x100
+
 
 #define PUSHLOOP_PLAIN(cx, s)                                          \
        cx->blk_loop.resetsp = s - PL_stack_base;                       \
        cx->blk_loop.my_op = cLOOP;                                     \
        cx->blk_loop.state_u.ary.ary = NULL;                            \
        cx->blk_loop.state_u.ary.ix = 0;                                \
-       cx->blk_loop.itervar_u.svp = NULL;
+        cx->cx_old_savestack_ix = PL_savestack_ix;                      \
+       cx->blk_loop.itervar_u.svp = NULL;                              \
+       cx->blk_loop.itersave = NULL;
+
+#ifdef USE_ITHREADS
+#  define PUSHLOOP_FOR_setpad(c) (c)->blk_loop.oldcomppad = PL_comppad
+#else
+#  define PUSHLOOP_FOR_setpad(c) NOOP
+#endif
 
-#define PUSHLOOP_FOR(cx, ivar, s)                                      \
+#define PUSHLOOP_FOR(cx, ivar, isave, s)                               \
        cx->blk_loop.resetsp = s - PL_stack_base;                       \
        cx->blk_loop.my_op = cLOOP;                                     \
        cx->blk_loop.state_u.ary.ary = NULL;                            \
        cx->blk_loop.state_u.ary.ix = 0;                                \
-       cx->blk_loop.itervar_u.svp = (SV**)(ivar);
+       cx->blk_loop.itervar_u.svp = (SV**)(ivar);                      \
+        cx->cx_old_savestack_ix = PL_savestack_ix;                      \
+        cx->blk_loop.itersave = isave;                                  \
+        PUSHLOOP_FOR_setpad(cx);
 
 #define POPLOOP(cx)                                                    \
        if (CxTYPE(cx) == CXt_LOOP_LAZYSV) {                            \
            SvREFCNT_dec_NN(cx->blk_loop.state_u.lazysv.cur);           \
            SvREFCNT_dec_NN(cx->blk_loop.state_u.lazysv.end);           \
        }                                                               \
-       if (CxTYPE(cx) == CXt_LOOP_FOR)                                 \
-           SvREFCNT_dec(cx->blk_loop.state_u.ary.ary);
+       else if (CxTYPE(cx) == CXt_LOOP_FOR)                            \
+           SvREFCNT_dec(cx->blk_loop.state_u.ary.ary);                 \
+        if (cx->cx_type & (CXp_FOR_PAD|CXp_FOR_GV)) {                   \
+            SV *cursv;                                                  \
+            SV **svp = (cx)->blk_loop.itervar_u.svp;                    \
+            if ((cx->cx_type & CXp_FOR_GV))                             \
+                svp = &GvSV((GV*)svp);                                  \
+            cursv = *svp;                                               \
+            *svp = cx->blk_loop.itersave;                               \
+            SvREFCNT_dec(cursv);                                        \
+        }
 
 /* given/when context */
 struct block_givwhen {
        OP *leave_op;
+        SV *defsv_save; /* the original $_ */
 };
 
-#define PUSHGIVEN(cx)                                                  \
+#define PUSHWHEN(cx)                                                   \
+        cx->cx_old_savestack_ix = PL_savestack_ix;                      \
        cx->blk_givwhen.leave_op = cLOGOP->op_other;
 
-#define PUSHWHEN PUSHGIVEN
+#define PUSHGIVEN(cx, orig_var)                                         \
+        PUSHWHEN(cx);                                                   \
+        cx->blk_givwhen.defsv_save = orig_var;
+
+#define POPWHEN(cx)                                                     \
+       NOOP;
+
+#define POPGIVEN(cx)                                                    \
+        SvREFCNT_dec(GvSV(PL_defgv));                                   \
+        GvSV(PL_defgv) = cx->blk_givwhen.defsv_save;
+
+
+/* basic block, i.e. pp_enter/leave */
+
+#define PUSHBASICBLK(cx)                                                \
+        cx->cx_old_savestack_ix = PL_savestack_ix;
+
+#define POPBASICBLK(cx)                                                 \
+       NOOP;
+
 
 /* context common to subroutines, evals and loops */
 struct block {
@@ -812,6 +887,7 @@ struct block {
     I32                blku_oldmarksp; /* mark stack index */
     I32                blku_oldscopesp;        /* scope stack index */
     PMOP *     blku_oldpm;     /* values of pattern match vars */
+    SSize_t     blku_old_tmpsfloor;     /* saved PL_tmps_floor */
 
     union {
        struct block_sub        blku_sub;
@@ -836,12 +912,14 @@ struct block {
 
 #define DEBUG_CX(action)                                               \
     DEBUG_l(                                                           \
-       Perl_deb(aTHX_ "CX %ld %s %s (scope %ld,%ld) at %s:%d\n",       \
+       Perl_deb(aTHX_ "CX %ld %s %s (scope %ld,%ld) (save %ld,%ld) at %s:%d\n",\
                    (long)cxstack_ix,                                   \
                    action,                                             \
                    PL_block_type[CxTYPE(&cxstack[cxstack_ix])],        \
                    (long)PL_scopestack_ix,                             \
                    (long)(cxstack[cxstack_ix].blk_oldscopesp),         \
+                   (long)PL_savestack_ix,                              \
+                   (long)(cxstack[cxstack_ix].cx_old_savestack_ix),    \
                    __FILE__, __LINE__));
 
 /* Enter a block. */
@@ -853,18 +931,23 @@ struct block {
        cx->blk_oldscopesp      = PL_scopestack_ix,                     \
        cx->blk_oldpm           = PL_curpm,                             \
        cx->blk_gimme           = (U8)gimme;                            \
+        cx->cx_u.cx_blk.blku_old_tmpsfloor = PL_tmps_floor;             \
+        PL_tmps_floor           = PL_tmps_ix;                           \
        DEBUG_CX("PUSH");
 
 /* Exit a block (RETURN and LAST). */
-#define POPBLOCK(cx,pm)                                                        \
+#define POPBLOCK(cx)                                                   \
        DEBUG_CX("POP");                                                \
-       cx = &cxstack[cxstack_ix--],                                    \
-       newsp            = PL_stack_base + cx->blk_oldsp,               \
        PL_curcop        = cx->blk_oldcop,                              \
        PL_markstack_ptr = PL_markstack + cx->blk_oldmarksp,            \
        PL_scopestack_ix = cx->blk_oldscopesp,                          \
-       pm               = cx->blk_oldpm,                               \
-       gimme            = cx->blk_gimme;
+        /* LEAVE_SCOPE() should have made this true. /(?{})/ cheats
+         * and leaves a CX entry lying around for repeated use, so
+         * skip for multicall */                  \
+        assert(   (CxTYPE(cx) == CXt_SUB && CxMULTICALL(cx))            \
+                || PL_savestack_ix == cx->cx_old_savestack_ix);         \
+        PL_tmps_floor = cx->cx_u.cx_blk.blku_old_tmpsfloor;             \
+       PL_curpm         = cx->blk_oldpm;
 
 /* Continue a block elsewhere (NEXT and REDO). */
 #define TOPBLOCK(cx)                                                   \
@@ -880,9 +963,8 @@ struct subst {
     U8         sbu_type;       /* what kind of context this is */
     U8         sbu_rflags;
     U16                sbu_rxtainted;  /* matches struct block */
-    I32                sbu_iters;
-    I32                sbu_maxiters;
-    I32                sbu_oldsave;
+    SSize_t    sbu_iters;
+    SSize_t    sbu_maxiters;
     char *     sbu_orig;
     SV *       sbu_dstr;
     SV *       sbu_targ;
@@ -895,7 +977,6 @@ struct subst {
 #define sb_iters       cx_u.cx_subst.sbu_iters
 #define sb_maxiters    cx_u.cx_subst.sbu_maxiters
 #define sb_rflags      cx_u.cx_subst.sbu_rflags
-#define sb_oldsave     cx_u.cx_subst.sbu_oldsave
 #define sb_rxtainted   cx_u.cx_subst.sbu_rxtainted
 #define sb_orig                cx_u.cx_subst.sbu_orig
 #define sb_dstr                cx_u.cx_subst.sbu_dstr
@@ -908,10 +989,10 @@ struct subst {
 
 #ifdef PERL_CORE
 #  define PUSHSUBST(cx) CXINC, cx = &cxstack[cxstack_ix],              \
+       cx->cx_old_savestack_ix = oldsave,                              \
        cx->sb_iters            = iters,                                \
        cx->sb_maxiters         = maxiters,                             \
        cx->sb_rflags           = r_flags,                              \
-       cx->sb_oldsave          = oldsave,                              \
        cx->sb_rxtainted        = rxtainted,                            \
        cx->sb_orig             = orig,                                 \
        cx->sb_dstr             = dstr,                                 \
@@ -923,16 +1004,19 @@ struct subst {
        cx->sb_rx               = rx,                                   \
        cx->cx_type             = CXt_SUBST | (once ? CXp_ONCE : 0);    \
        rxres_save(&cx->sb_rxres, rx);                                  \
-       (void)ReREFCNT_inc(rx)
+       (void)ReREFCNT_inc(rx);                                         \
+        SvREFCNT_inc_void_NN(targ)
 
-#  define POPSUBST(cx) cx = &cxstack[cxstack_ix--];                    \
+#  define POPSUBST(cx) \
        rxres_free(&cx->sb_rxres);                                      \
-       ReREFCNT_dec(cx->sb_rx)
+       ReREFCNT_dec(cx->sb_rx);                                        \
+        SvREFCNT_dec_NN(cx->sb_targ)
 #endif
 
 #define CxONCE(cx)             ((cx)->cx_type & CXp_ONCE)
 
 struct context {
+    I32                        cx_old_savestack_ix;   /* saved PL_savestack_ix */
     union {
        struct block    cx_blk;
        struct subst    cx_subst;
@@ -943,7 +1027,7 @@ struct context {
 /* If you re-order these, there is also an array of uppercase names in perl.h
    and a static array of context names in pp_ctl.c  */
 #define CXTYPEMASK     0xf
-#define CXt_NULL       0
+#define CXt_NULL       0 /* currently only used for sort BLOCK */
 #define CXt_WHEN       1
 #define CXt_BLOCK      2
 /* When micro-optimising :-) keep GIVEN next to the LOOPs, as these 5 share a
@@ -962,14 +1046,9 @@ struct context {
 #define CXt_SUBST      11
 /* SUBST doesn't feature in all switch statements.  */
 
-/* private flags for CXt_SUB and CXt_NULL
-   However, this is checked in many places which do not check the type, so
-   this bit needs to be kept clear for most everything else. For reasons I
-   haven't investigated, it can coexist with CXp_FOR_DEF */
-#define CXp_MULTICALL  0x10    /* part of a multicall (so don't
-                                  tear down context on exit). */ 
-
 /* private flags for CXt_SUB and CXt_FORMAT */
+#define CXp_MULTICALL  0x10    /* part of a multicall (so don't tear down
+                                   context on exit). (not CXt_FORMAT) */
 #define CXp_HASARGS    0x20
 #define CXp_SUB_RE     0x40    /* code called within regex, i.e. (?{}) */
 #define CXp_SUB_RE_FAKE        0x80    /* fake sub CX for (?{}) in current scope */
@@ -980,15 +1059,17 @@ struct context {
 
 /* private flags for CXt_LOOP */
 #define CXp_FOR_DEF    0x10    /* foreach using $_ */
-#define CxPADLOOP(c)   ((c)->blk_loop.my_op->op_targ)
+#define CXp_FOR_LVREF  0x20    /* foreach using \$var */
+#define CXp_FOR_GV     0x40    /* foreach using package var */
+#define CXp_FOR_PAD    0x80    /* foreach using lexical var */
+#define CxPADLOOP(c)   ((c)->cx_type & CXp_FOR_PAD)
 
 /* private flags for CXt_SUBST */
 #define CXp_ONCE       0x10    /* What was sbu_once in struct subst */
 
 #define CxTYPE(c)      ((c)->cx_type & CXTYPEMASK)
 #define CxTYPE_is_LOOP(c)      (((c)->cx_type & 0xC) == 0x4)
-#define CxMULTICALL(c) (((c)->cx_type & CXp_MULTICALL)                 \
-                        == CXp_MULTICALL)
+#define CxMULTICALL(c) ((c)->cx_type & CXp_MULTICALL)
 #define CxREALEVAL(c)  (((c)->cx_type & (CXTYPEMASK|CXp_REAL))         \
                         == (CXt_EVAL|CXp_REAL))
 #define CxTRYBLOCK(c)  (((c)->cx_type & (CXTYPEMASK|CXp_TRYBLOCK))     \
@@ -1005,15 +1086,15 @@ struct context {
 
 /*
 =for apidoc AmU||G_SCALAR
-Used to indicate scalar context.  See C<GIMME_V>, C<GIMME>, and
+Used to indicate scalar context.  See C<L</GIMME_V>>, C<L</GIMME>>, and
 L<perlcall>.
 
 =for apidoc AmU||G_ARRAY
-Used to indicate list context.  See C<GIMME_V>, C<GIMME> and
+Used to indicate list context.  See C<L</GIMME_V>>, C<L</GIMME>> and
 L<perlcall>.
 
 =for apidoc AmU||G_VOID
-Used to indicate void context.  See C<GIMME_V> and L<perlcall>.
+Used to indicate void context.  See C<L</GIMME_V>> and L<perlcall>.
 
 =for apidoc AmU||G_DISCARD
 Indicates that arguments returned from a callback should be discarded.  See
@@ -1079,6 +1160,7 @@ L<perlcall>.
 #define PERLSI_WARNHOOK                7
 #define PERLSI_DIEHOOK         8
 #define PERLSI_REQUIRE         9
+#define PERLSI_MULTICALL       10
 
 struct stackinfo {
     AV *               si_stack;       /* stack for current runlevel */
@@ -1198,22 +1280,22 @@ See L<perlcall/LIGHTWEIGHT CALLBACKS>.
        CV * const _nOnclAshIngNamE_ = the_cv;                          \
        CV * const cv = _nOnclAshIngNamE_;                              \
        PADLIST * const padlist = CvPADLIST(cv);                        \
-       ENTER;                                                          \
        multicall_oldcatch = CATCH_GET;                                 \
-       SAVETMPS; SAVEVPTR(PL_op);                                      \
        CATCH_SET(TRUE);                                                \
-       PUSHSTACKi(PERLSI_SORT);                                        \
+       PUSHSTACKi(PERLSI_MULTICALL);                                   \
        PUSHBLOCK(cx, (CXt_SUB|CXp_MULTICALL|flags), PL_stack_sp);      \
        PUSHSUB(cx);                                                    \
+        cx->cx_old_savestack_ix = PL_savestack_ix;                      \
+       SAVEVPTR(PL_op);                                                \
         if (!(flags & CXp_SUB_RE_FAKE))                                 \
             CvDEPTH(cv)++;                                             \
        if (CvDEPTH(cv) >= 2) {                                         \
            PERL_STACK_OVERFLOW_CHECK();                                \
            Perl_pad_push(aTHX_ padlist, CvDEPTH(cv));                  \
        }                                                               \
-       SAVECOMPPAD();                                                  \
        PAD_SET_CUR_NOSAVE(padlist, CvDEPTH(cv));                       \
        multicall_cv = cv;                                              \
+        PERL_UNUSED_VAR(multicall_cv); /* for API */                    \
        multicall_cop = CvSTART(cv);                                    \
     } STMT_END
 
@@ -1226,13 +1308,16 @@ See L<perlcall/LIGHTWEIGHT CALLBACKS>.
 #define POP_MULTICALL \
     STMT_START {                                                       \
        cx = &cxstack[cxstack_ix];                                      \
-        if (! ((CvDEPTH(multicall_cv) = cx->blk_sub.olddepth)) ) {     \
-               LEAVESUB(multicall_cv);                                 \
-       }                                                               \
-       POPBLOCK(cx,PL_curpm);                                          \
+       CX_LEAVE_SCOPE(cx);                                             \
+        POPSUB_COMMON(cx);                                              \
+        newsp = PL_stack_base + cx->blk_oldsp;                          \
+        gimme = cx->blk_gimme;                                          \
+        PERL_UNUSED_VAR(newsp); /* for API */                           \
+        PERL_UNUSED_VAR(gimme); /* for API */                           \
+       POPBLOCK(cx);                                                   \
+       CX_POP(cx);                                                     \
        POPSTACK;                                                       \
        CATCH_SET(multicall_oldcatch);                                  \
-       LEAVE;                                                          \
        SPAGAIN;                                                        \
     } STMT_END
 
@@ -1245,29 +1330,20 @@ See L<perlcall/LIGHTWEIGHT CALLBACKS>.
        CV * const cv = _nOnclAshIngNamE_;                              \
        PADLIST * const padlist = CvPADLIST(cv);                        \
        cx = &cxstack[cxstack_ix];                                      \
-       assert(cx->cx_type & CXp_MULTICALL);                            \
-       if (! ((CvDEPTH(multicall_cv) = cx->blk_sub.olddepth)) ) {      \
-               LEAVESUB(multicall_cv);                                 \
-       }                                                               \
+       assert(CxMULTICALL(cx));                                        \
+        POPSUB_COMMON(cx);                                              \
        cx->cx_type = (CXt_SUB|CXp_MULTICALL|flags);                    \
-       PUSHSUB(cx);                                                    \
+        PUSHSUB(cx);                                                   \
         if (!(flags & CXp_SUB_RE_FAKE))                                 \
             CvDEPTH(cv)++;                                             \
        if (CvDEPTH(cv) >= 2) {                                         \
            PERL_STACK_OVERFLOW_CHECK();                                \
            Perl_pad_push(aTHX_ padlist, CvDEPTH(cv));                  \
        }                                                               \
-       SAVECOMPPAD();                                                  \
        PAD_SET_CUR_NOSAVE(padlist, CvDEPTH(cv));                       \
        multicall_cv = cv;                                              \
        multicall_cop = CvSTART(cv);                                    \
     } STMT_END
 /*
- * Local variables:
- * c-indentation-style: bsd
- * c-basic-offset: 4
- * indent-tabs-mode: nil
- * End:
- *
  * ex: set ts=8 sts=4 sw=4 et:
  */