add some SvTRUE() benchmarks

[perl5.git] / pp_ctl.c

/*    pp_ctl.c
 *
 *    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
 *    2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 *      Now far ahead the Road has gone,
 *          And I must follow, if I can,
 *      Pursuing it with eager feet,
 *          Until it joins some larger way
 *      Where many paths and errands meet.
 *          And whither then?  I cannot say.
 *
 *     [Bilbo on p.35 of _The Lord of the Rings_, I/i: "A Long-Expected Party"]
 */

/* This file contains control-oriented pp ("push/pop") functions that
 * execute the opcodes that make up a perl program. A typical pp function
 * expects to find its arguments on the stack, and usually pushes its
 * results onto the stack, hence the 'pp' terminology. Each OP structure
 * contains a pointer to the relevant pp_foo() function.
 *
 * Control-oriented means things like pp_enteriter() and pp_next(), which
 * alter the flow of control of the program.
 */


#include "EXTERN.h"
#define PERL_IN_PP_CTL_C
#include "perl.h"

#define RUN_PP_CATCHABLY(thispp) \
    STMT_START { if (CATCH_GET) return docatch(thispp); } STMT_END

#define dopoptosub(plop)	dopoptosub_at(cxstack, (plop))

PP(pp_wantarray)
{
    dSP;
    I32 cxix;
    const PERL_CONTEXT *cx;
    EXTEND(SP, 1);

    if (PL_op->op_private & OPpOFFBYONE) {
	if (!(cx = caller_cx(1,NULL))) RETPUSHUNDEF;
    }
    else {
      cxix = dopoptosub(cxstack_ix);
      if (cxix < 0)
	RETPUSHUNDEF;
      cx = &cxstack[cxix];
    }

    switch (cx->blk_gimme) {
    case G_ARRAY:
	RETPUSHYES;
    case G_SCALAR:
	RETPUSHNO;
    default:
	RETPUSHUNDEF;
    }
}

PP(pp_regcreset)
{
    TAINT_NOT;
    return NORMAL;
}

PP(pp_regcomp)
{
    dSP;
    PMOP *pm = (PMOP*)cLOGOP->op_other;
    SV **args;
    int nargs;
    REGEXP *re = NULL;
    REGEXP *new_re;
    const regexp_engine *eng;
    bool is_bare_re= FALSE;

    if (PL_op->op_flags & OPf_STACKED) {
	dMARK;
	nargs = SP - MARK;
	args  = ++MARK;
    }
    else {
	nargs = 1;
	args  = SP;
    }

    /* prevent recompiling under /o and ithreads. */
#if defined(USE_ITHREADS)
    if (pm->op_pmflags & PMf_KEEP && PM_GETRE(pm)) {
	SP = args-1;
	RETURN;
    }
#endif

    re = PM_GETRE(pm);
    assert (re != (REGEXP*) &PL_sv_undef);
    eng = re ? RX_ENGINE(re) : current_re_engine();

    new_re = (eng->op_comp
		    ? eng->op_comp
		    : &Perl_re_op_compile
	    )(aTHX_ args, nargs, pm->op_code_list, eng, re,
		&is_bare_re,
                (pm->op_pmflags & RXf_PMf_FLAGCOPYMASK),
		pm->op_pmflags |
		    (PL_op->op_flags & OPf_SPECIAL ? PMf_USE_RE_EVAL : 0));

    if (pm->op_pmflags & PMf_HAS_CV)
	ReANY(new_re)->qr_anoncv
			= (CV*) SvREFCNT_inc(PAD_SV(PL_op->op_targ));

    if (is_bare_re) {
	REGEXP *tmp;
	/* The match's LHS's get-magic might need to access this op's regexp
	   (e.g. $' =~ /$re/ while foo; see bug 70764).  So we must call
	   get-magic now before we replace the regexp. Hopefully this hack can
	   be replaced with the approach described at
	   http://www.nntp.perl.org/group/perl.perl5.porters/2007/03/msg122415.html
	   some day. */
	if (pm->op_type == OP_MATCH) {
	    SV *lhs;
	    const bool was_tainted = TAINT_get;
	    if (pm->op_flags & OPf_STACKED)
		lhs = args[-1];
	    else if (pm->op_targ)
		lhs = PAD_SV(pm->op_targ);
	    else lhs = DEFSV;
	    SvGETMAGIC(lhs);
	    /* Restore the previous value of PL_tainted (which may have been
	       modified by get-magic), to avoid incorrectly setting the
	       RXf_TAINTED flag with RX_TAINT_on further down. */
	    TAINT_set(was_tainted);
#ifdef NO_TAINT_SUPPORT
            PERL_UNUSED_VAR(was_tainted);
#endif
	}
	tmp = reg_temp_copy(NULL, new_re);
	ReREFCNT_dec(new_re);
	new_re = tmp;
    }

    if (re != new_re) {
	ReREFCNT_dec(re);
	PM_SETRE(pm, new_re);
    }


    assert(TAINTING_get || !TAINT_get);
    if (TAINT_get) {
	SvTAINTED_on((SV*)new_re);
        RX_TAINT_on(new_re);
    }

    /* handle the empty pattern */
    if (!RX_PRELEN(PM_GETRE(pm)) && PL_curpm) {
        if (PL_curpm == PL_reg_curpm) {
            if (PL_curpm_under) {
                if (PL_curpm_under == PL_reg_curpm) {
                    Perl_croak(aTHX_ "Infinite recursion via empty pattern");
                } else {
                    pm = PL_curpm_under;
                }
            }
        } else {
            pm = PL_curpm;
        }
    }

#if !defined(USE_ITHREADS)
    /* can't change the optree at runtime either */
    /* PMf_KEEP is handled differently under threads to avoid these problems */
    if (pm->op_pmflags & PMf_KEEP) {
	cLOGOP->op_first->op_next = PL_op->op_next;
    }
#endif

    SP = args-1;
    RETURN;
}


PP(pp_substcont)
{
    dSP;
    PERL_CONTEXT *cx = CX_CUR();
    PMOP * const pm = (PMOP*) cLOGOP->op_other;
    SV * const dstr = cx->sb_dstr;
    char *s = cx->sb_s;
    char *m = cx->sb_m;
    char *orig = cx->sb_orig;
    REGEXP * const rx = cx->sb_rx;
    SV *nsv = NULL;
    REGEXP *old = PM_GETRE(pm);

    PERL_ASYNC_CHECK();

    if(old != rx) {
	if(old)
	    ReREFCNT_dec(old);
	PM_SETRE(pm,ReREFCNT_inc(rx));
    }

    rxres_restore(&cx->sb_rxres, rx);

    if (cx->sb_iters++) {
	const SSize_t saviters = cx->sb_iters;
	if (cx->sb_iters > cx->sb_maxiters)
	    DIE(aTHX_ "Substitution loop");

	SvGETMAGIC(TOPs); /* possibly clear taint on $1 etc: #67962 */

    	/* See "how taint works" above pp_subst() */
	if (SvTAINTED(TOPs))
	    cx->sb_rxtainted |= SUBST_TAINT_REPL;
	sv_catsv_nomg(dstr, POPs);
	if (CxONCE(cx) || s < orig ||
                !CALLREGEXEC(rx, s, cx->sb_strend, orig,
			     (s == m), cx->sb_targ, NULL,
                    (REXEC_IGNOREPOS|REXEC_NOT_FIRST|REXEC_FAIL_ON_UNDERFLOW)))
	{
	    SV *targ = cx->sb_targ;

	    assert(cx->sb_strend >= s);
	    if(cx->sb_strend > s) {
		 if (DO_UTF8(dstr) && !SvUTF8(targ))
		      sv_catpvn_nomg_utf8_upgrade(dstr, s, cx->sb_strend - s, nsv);
		 else
		      sv_catpvn_nomg(dstr, s, cx->sb_strend - s);
	    }
	    if (RX_MATCH_TAINTED(rx)) /* run time pattern taint, eg locale */
		cx->sb_rxtainted |= SUBST_TAINT_PAT;

	    if (pm->op_pmflags & PMf_NONDESTRUCT) {
		PUSHs(dstr);
		/* From here on down we're using the copy, and leaving the
		   original untouched.  */
		targ = dstr;
	    }
	    else {
		SV_CHECK_THINKFIRST_COW_DROP(targ);
		if (isGV(targ)) Perl_croak_no_modify();
		SvPV_free(targ);
		SvPV_set(targ, SvPVX(dstr));
		SvCUR_set(targ, SvCUR(dstr));
		SvLEN_set(targ, SvLEN(dstr));
		if (DO_UTF8(dstr))
		    SvUTF8_on(targ);
		SvPV_set(dstr, NULL);

		PL_tainted = 0;
		mPUSHi(saviters - 1);

		(void)SvPOK_only_UTF8(targ);
	    }

	    /* update the taint state of various various variables in
	     * preparation for final exit.
	     * See "how taint works" above pp_subst() */
	    if (TAINTING_get) {
		if ((cx->sb_rxtainted & SUBST_TAINT_PAT) ||
		    ((cx->sb_rxtainted & (SUBST_TAINT_STR|SUBST_TAINT_RETAINT))
				    == (SUBST_TAINT_STR|SUBST_TAINT_RETAINT))
		)
		    (RX_MATCH_TAINTED_on(rx)); /* taint $1 et al */

		if (!(cx->sb_rxtainted & SUBST_TAINT_BOOLRET)
		    && (cx->sb_rxtainted & (SUBST_TAINT_STR|SUBST_TAINT_PAT))
		)
		    SvTAINTED_on(TOPs);  /* taint return value */
		/* needed for mg_set below */
		TAINT_set(
                    cBOOL(cx->sb_rxtainted &
			  (SUBST_TAINT_STR|SUBST_TAINT_PAT|SUBST_TAINT_REPL))
                );
		SvTAINT(TARG);
	    }
	    /* PL_tainted must be correctly set for this mg_set */
	    SvSETMAGIC(TARG);
	    TAINT_NOT;

	    CX_LEAVE_SCOPE(cx);
	    CX_POPSUBST(cx);
            CX_POP(cx);

	    PERL_ASYNC_CHECK();
	    RETURNOP(pm->op_next);
	    NOT_REACHED; /* NOTREACHED */
	}
	cx->sb_iters = saviters;
    }
    if (RX_MATCH_COPIED(rx) && RX_SUBBEG(rx) != orig) {
	m = s;
	s = orig;
        assert(!RX_SUBOFFSET(rx));
	cx->sb_orig = orig = RX_SUBBEG(rx);
	s = orig + (m - s);
	cx->sb_strend = s + (cx->sb_strend - m);
    }
    cx->sb_m = m = RX_OFFS(rx)[0].start + orig;
    if (m > s) {
	if (DO_UTF8(dstr) && !SvUTF8(cx->sb_targ))
	    sv_catpvn_nomg_utf8_upgrade(dstr, s, m - s, nsv);
	else
	    sv_catpvn_nomg(dstr, s, m-s);
    }
    cx->sb_s = RX_OFFS(rx)[0].end + orig;
    { /* Update the pos() information. */
	SV * const sv
	    = (pm->op_pmflags & PMf_NONDESTRUCT) ? cx->sb_dstr : cx->sb_targ;
	MAGIC *mg;

        /* the string being matched against may no longer be a string,
         * e.g. $_=0; s/.../$_++/ge */

        if (!SvPOK(sv))
            SvPV_force_nomg_nolen(sv);

	if (!(mg = mg_find_mglob(sv))) {
	    mg = sv_magicext_mglob(sv);
	}
	MgBYTEPOS_set(mg, sv, SvPVX(sv), m - orig);
    }
    if (old != rx)
	(void)ReREFCNT_inc(rx);
    /* update the taint state of various various variables in preparation
     * for calling the code block.
     * See "how taint works" above pp_subst() */
    if (TAINTING_get) {
	if (RX_MATCH_TAINTED(rx)) /* run time pattern taint, eg locale */
	    cx->sb_rxtainted |= SUBST_TAINT_PAT;

	if ((cx->sb_rxtainted & SUBST_TAINT_PAT) ||
	    ((cx->sb_rxtainted & (SUBST_TAINT_STR|SUBST_TAINT_RETAINT))
			    == (SUBST_TAINT_STR|SUBST_TAINT_RETAINT))
	)
	    (RX_MATCH_TAINTED_on(rx)); /* taint $1 et al */

	if (cx->sb_iters > 1 && (cx->sb_rxtainted & 
			(SUBST_TAINT_STR|SUBST_TAINT_PAT|SUBST_TAINT_REPL)))
	    SvTAINTED_on((pm->op_pmflags & PMf_NONDESTRUCT)
			 ? cx->sb_dstr : cx->sb_targ);
	TAINT_NOT;
    }
    rxres_save(&cx->sb_rxres, rx);
    PL_curpm = pm;
    RETURNOP(pm->op_pmstashstartu.op_pmreplstart);
}

void
Perl_rxres_save(pTHX_ void **rsp, REGEXP *rx)
{
    UV *p = (UV*)*rsp;
    U32 i;

    PERL_ARGS_ASSERT_RXRES_SAVE;
    PERL_UNUSED_CONTEXT;

    if (!p || p[1] < RX_NPARENS(rx)) {
#ifdef PERL_ANY_COW
	i = 7 + (RX_NPARENS(rx)+1) * 2;
#else
	i = 6 + (RX_NPARENS(rx)+1) * 2;
#endif
	if (!p)
	    Newx(p, i, UV);
	else
	    Renew(p, i, UV);
	*rsp = (void*)p;
    }

    /* what (if anything) to free on croak */
    *p++ = PTR2UV(RX_MATCH_COPIED(rx) ? RX_SUBBEG(rx) : NULL);
    RX_MATCH_COPIED_off(rx);
    *p++ = RX_NPARENS(rx);

#ifdef PERL_ANY_COW
    *p++ = PTR2UV(RX_SAVED_COPY(rx));
    RX_SAVED_COPY(rx) = NULL;
#endif

    *p++ = PTR2UV(RX_SUBBEG(rx));
    *p++ = (UV)RX_SUBLEN(rx);
    *p++ = (UV)RX_SUBOFFSET(rx);
    *p++ = (UV)RX_SUBCOFFSET(rx);
    for (i = 0; i <= RX_NPARENS(rx); ++i) {
	*p++ = (UV)RX_OFFS(rx)[i].start;
	*p++ = (UV)RX_OFFS(rx)[i].end;
    }
}

static void
S_rxres_restore(pTHX_ void **rsp, REGEXP *rx)
{
    UV *p = (UV*)*rsp;
    U32 i;

    PERL_ARGS_ASSERT_RXRES_RESTORE;
    PERL_UNUSED_CONTEXT;

    RX_MATCH_COPY_FREE(rx);
    RX_MATCH_COPIED_set(rx, *p);
    *p++ = 0;
    RX_NPARENS(rx) = *p++;

#ifdef PERL_ANY_COW
    if (RX_SAVED_COPY(rx))
	SvREFCNT_dec (RX_SAVED_COPY(rx));
    RX_SAVED_COPY(rx) = INT2PTR(SV*,*p);
    *p++ = 0;
#endif

    RX_SUBBEG(rx) = INT2PTR(char*,*p++);
    RX_SUBLEN(rx) = (I32)(*p++);
    RX_SUBOFFSET(rx) = (I32)*p++;
    RX_SUBCOFFSET(rx) = (I32)*p++;
    for (i = 0; i <= RX_NPARENS(rx); ++i) {
	RX_OFFS(rx)[i].start = (I32)(*p++);
	RX_OFFS(rx)[i].end = (I32)(*p++);
    }
}

static void
S_rxres_free(pTHX_ void **rsp)
{
    UV * const p = (UV*)*rsp;

    PERL_ARGS_ASSERT_RXRES_FREE;
    PERL_UNUSED_CONTEXT;

    if (p) {
	void *tmp = INT2PTR(char*,*p);
#ifdef PERL_POISON
#ifdef PERL_ANY_COW
	U32 i = 9 + p[1] * 2;
#else
	U32 i = 8 + p[1] * 2;
#endif
#endif

#ifdef PERL_ANY_COW
        SvREFCNT_dec (INT2PTR(SV*,p[2]));
#endif
#ifdef PERL_POISON
        PoisonFree(p, i, sizeof(UV));
#endif

	Safefree(tmp);
	Safefree(p);
	*rsp = NULL;
    }
}

#define FORM_NUM_BLANK (1<<30)
#define FORM_NUM_POINT (1<<29)

PP(pp_formline)
{
    dSP; dMARK; dORIGMARK;
    SV * const tmpForm = *++MARK;
    SV *formsv;		    /* contains text of original format */
    U32 *fpc;	    /* format ops program counter */
    char *t;	    /* current append position in target string */
    const char *f;	    /* current position in format string */
    I32 arg;
    SV *sv = NULL; /* current item */
    const char *item = NULL;/* string value of current item */
    I32 itemsize  = 0;	    /* length (chars) of item, possibly truncated */
    I32 itembytes = 0;	    /* as itemsize, but length in bytes */
    I32 fieldsize = 0;	    /* width of current field */
    I32 lines = 0;	    /* number of lines that have been output */
    bool chopspace = (strchr(PL_chopset, ' ') != NULL); /* does $: have space */
    const char *chophere = NULL; /* where to chop current item */
    STRLEN linemark = 0;    /* pos of start of line in output */
    NV value;
    bool gotsome = FALSE;   /* seen at least one non-blank item on this line */
    STRLEN len;             /* length of current sv */
    STRLEN linemax;	    /* estimate of output size in bytes */
    bool item_is_utf8 = FALSE;
    bool targ_is_utf8 = FALSE;
    const char *fmt;
    MAGIC *mg = NULL;
    U8 *source;		    /* source of bytes to append */
    STRLEN to_copy;	    /* how may bytes to append */
    char trans;		    /* what chars to translate */
    bool copied_form = FALSE; /* have we duplicated the form? */

    mg = doparseform(tmpForm);

    fpc = (U32*)mg->mg_ptr;
    /* the actual string the format was compiled from.
     * with overload etc, this may not match tmpForm */
    formsv = mg->mg_obj;


    SvPV_force(PL_formtarget, len);
    if (SvTAINTED(tmpForm) || SvTAINTED(formsv))
	SvTAINTED_on(PL_formtarget);
    if (DO_UTF8(PL_formtarget))
	targ_is_utf8 = TRUE;
    /* this is an initial estimate of how much output buffer space
     * to allocate. It may be exceeded later */
    linemax = (SvCUR(formsv) * (IN_BYTES ? 1 : 3) + 1);
    t = SvGROW(PL_formtarget, len + linemax + 1);
    /* XXX from now onwards, SvCUR(PL_formtarget) is invalid */
    t += len;
    f = SvPV_const(formsv, len);

    for (;;) {
	DEBUG_f( {
	    const char *name = "???";
	    arg = -1;
	    switch (*fpc) {
	    case FF_LITERAL:	arg = fpc[1]; name = "LITERAL";	break;
	    case FF_BLANK:	arg = fpc[1]; name = "BLANK";	break;
	    case FF_SKIP:	arg = fpc[1]; name = "SKIP";	break;
	    case FF_FETCH:	arg = fpc[1]; name = "FETCH";	break;
	    case FF_DECIMAL:	arg = fpc[1]; name = "DECIMAL";	break;

	    case FF_CHECKNL:	name = "CHECKNL";	break;
	    case FF_CHECKCHOP:	name = "CHECKCHOP";	break;
	    case FF_SPACE:	name = "SPACE";		break;
	    case FF_HALFSPACE:	name = "HALFSPACE";	break;
	    case FF_ITEM:	name = "ITEM";		break;
	    case FF_CHOP:	name = "CHOP";		break;
	    case FF_LINEGLOB:	name = "LINEGLOB";	break;
	    case FF_NEWLINE:	name = "NEWLINE";	break;
	    case FF_MORE:	name = "MORE";		break;
	    case FF_LINEMARK:	name = "LINEMARK";	break;
	    case FF_END:	name = "END";		break;
	    case FF_0DECIMAL:	name = "0DECIMAL";	break;
	    case FF_LINESNGL:	name = "LINESNGL";	break;
	    }
	    if (arg >= 0)
		PerlIO_printf(Perl_debug_log, "%-16s%ld\n", name, (long) arg);
	    else
		PerlIO_printf(Perl_debug_log, "%-16s\n", name);
	} );
	switch (*fpc++) {
	case FF_LINEMARK: /* start (or end) of a line */
	    linemark = t - SvPVX(PL_formtarget);
	    lines++;
	    gotsome = FALSE;
	    break;

	case FF_LITERAL: /* append <arg> literal chars */
	    to_copy = *fpc++;
	    source = (U8 *)f;
	    f += to_copy;
	    trans = '~';
	    item_is_utf8 = targ_is_utf8 ? !!DO_UTF8(formsv) : !!SvUTF8(formsv);
	    goto append;

	case FF_SKIP: /* skip <arg> chars in format */
	    f += *fpc++;
	    break;

	case FF_FETCH: /* get next item and set field size to <arg> */
	    arg = *fpc++;
	    f += arg;
	    fieldsize = arg;

	    if (MARK < SP)
		sv = *++MARK;
	    else {
		sv = &PL_sv_no;
		Perl_ck_warner(aTHX_ packWARN(WARN_SYNTAX), "Not enough format arguments");
	    }
	    if (SvTAINTED(sv))
		SvTAINTED_on(PL_formtarget);
	    break;

	case FF_CHECKNL: /* find max len of item (up to \n) that fits field */
	    {
		const char *s = item = SvPV_const(sv, len);
		const char *send = s + len;

                itemsize = 0;
		item_is_utf8 = DO_UTF8(sv);
                while (s < send) {
                    if (!isCNTRL(*s))
                        gotsome = TRUE;
                    else if (*s == '\n')
                        break;

                    if (item_is_utf8)
                        s += UTF8SKIP(s);
                    else
                        s++;
                    itemsize++;
                    if (itemsize == fieldsize)
                        break;
                }
                itembytes = s - item;
                chophere = s;
		break;
	    }

	case FF_CHECKCHOP: /* like CHECKNL, but up to highest split point */
	    {
		const char *s = item = SvPV_const(sv, len);
		const char *send = s + len;
                I32 size = 0;

                chophere = NULL;
		item_is_utf8 = DO_UTF8(sv);
                while (s < send) {
                    /* look for a legal split position */
                    if (isSPACE(*s)) {
                        if (*s == '\r') {
                            chophere = s;
                            itemsize = size;
                            break;
                        }
                        if (chopspace) {
                            /* provisional split point */
                            chophere = s;
                            itemsize = size;
                        }
                        /* we delay testing fieldsize until after we've
                         * processed the possible split char directly
                         * following the last field char; so if fieldsize=3
                         * and item="a b cdef", we consume "a b", not "a".
                         * Ditto further down.
                         */
                        if (size == fieldsize)
                            break;
                    }
                    else {
                        if (strchr(PL_chopset, *s)) {
                            /* provisional split point */
                            /* for a non-space split char, we include
                             * the split char; hence the '+1' */
                            chophere = s + 1;
                            itemsize = size;
                        }
                        if (size == fieldsize)
                            break;
                        if (!isCNTRL(*s))
                            gotsome = TRUE;
                    }

                    if (item_is_utf8)
                        s += UTF8SKIP(s);
                    else
                        s++;
                    size++;
                }
                if (!chophere || s == send) {
                    chophere = s;
                    itemsize = size;
                }
                itembytes = chophere - item;

		break;
	    }

	case FF_SPACE: /* append padding space (diff of field, item size) */
	    arg = fieldsize - itemsize;
	    if (arg) {
		fieldsize -= arg;
		while (arg-- > 0)
		    *t++ = ' ';
	    }
	    break;

	case FF_HALFSPACE: /* like FF_SPACE, but only append half as many */
	    arg = fieldsize - itemsize;
	    if (arg) {
		arg /= 2;
		fieldsize -= arg;
		while (arg-- > 0)
		    *t++ = ' ';
	    }
	    break;

	case FF_ITEM: /* append a text item, while blanking ctrl chars */
	    to_copy = itembytes;
	    source = (U8 *)item;
	    trans = 1;
	    goto append;

	case FF_CHOP: /* (for ^*) chop the current item */
	    if (sv != &PL_sv_no) {
		const char *s = chophere;
                if (!copied_form &&
                    ((sv == tmpForm || SvSMAGICAL(sv))
                     || (SvGMAGICAL(tmpForm) && !sv_only_taint_gmagic(tmpForm))) ) {
                    /* sv and tmpForm are either the same SV, or magic might allow modification
                       of tmpForm when sv is modified, so copy */
                    SV *newformsv = sv_mortalcopy(formsv);
                    U32 *new_compiled;

                    f = SvPV_nolen(newformsv) + (f - SvPV_nolen(formsv));
                    Newx(new_compiled, mg->mg_len / sizeof(U32), U32);
                    memcpy(new_compiled, mg->mg_ptr, mg->mg_len);
                    SAVEFREEPV(new_compiled);
                    fpc = new_compiled + (fpc - (U32*)mg->mg_ptr);
                    formsv = newformsv;

                    copied_form = TRUE;
                }
		if (chopspace) {
		    while (isSPACE(*s))
			s++;
		}
                if (SvPOKp(sv))
                    sv_chop(sv,s);
                else
                    /* tied, overloaded or similar strangeness.
                     * Do it the hard way */
                    sv_setpvn(sv, s, len - (s-item));
		SvSETMAGIC(sv);
		break;
	    }

	case FF_LINESNGL: /* process ^*  */
	    chopspace = 0;
            /* FALLTHROUGH */

	case FF_LINEGLOB: /* process @*  */
	    {
		const bool oneline = fpc[-1] == FF_LINESNGL;
		const char *s = item = SvPV_const(sv, len);
		const char *const send = s + len;

		item_is_utf8 = DO_UTF8(sv);
		chophere = s + len;
		if (!len)
		    break;
		trans = 0;
		gotsome = TRUE;
		source = (U8 *) s;
		to_copy = len;
		while (s < send) {
		    if (*s++ == '\n') {
			if (oneline) {
			    to_copy = s - item - 1;
			    chophere = s;
			    break;
			} else {
			    if (s == send) {
				to_copy--;
			    } else
				lines++;
			}
		    }
		}
	    }

	append:
	    /* append to_copy bytes from source to PL_formstring.
	     * item_is_utf8 implies source is utf8.
	     * if trans, translate certain characters during the copy */
	    {
		U8 *tmp = NULL;
		STRLEN grow = 0;

		SvCUR_set(PL_formtarget,
			  t - SvPVX_const(PL_formtarget));

		if (targ_is_utf8 && !item_is_utf8) {
		    source = tmp = bytes_to_utf8(source, &to_copy);
                    grow = to_copy;
		} else {
		    if (item_is_utf8 && !targ_is_utf8) {
			U8 *s;
			/* Upgrade targ to UTF8, and then we reduce it to
			   a problem we have a simple solution for.
			   Don't need get magic.  */
			sv_utf8_upgrade_nomg(PL_formtarget);
			targ_is_utf8 = TRUE;
			/* re-calculate linemark */
			s = (U8*)SvPVX(PL_formtarget);
			/* the bytes we initially allocated to append the
			 * whole line may have been gobbled up during the
			 * upgrade, so allocate a whole new line's worth
			 * for safety */
			grow = linemax;
			while (linemark--)
			    s += UTF8SKIP(s);
			linemark = s - (U8*)SvPVX(PL_formtarget);
		    }
		    /* Easy. They agree.  */
		    assert (item_is_utf8 == targ_is_utf8);
		}
		if (!trans)
		    /* @* and ^* are the only things that can exceed
		     * the linemax, so grow by the output size, plus
		     * a whole new form's worth in case of any further
		     * output */
		    grow = linemax + to_copy;
		if (grow)
		    SvGROW(PL_formtarget, SvCUR(PL_formtarget) + grow + 1);
		t = SvPVX(PL_formtarget) + SvCUR(PL_formtarget);

		Copy(source, t, to_copy, char);
		if (trans) {
		    /* blank out ~ or control chars, depending on trans.
		     * works on bytes not chars, so relies on not
		     * matching utf8 continuation bytes */
		    U8 *s = (U8*)t;
		    U8 *send = s + to_copy;
		    while (s < send) {
			const int ch = *s;
			if (trans == '~' ? (ch == '~') : isCNTRL(ch))
			    *s = ' ';
			s++;
		    }
		}

		t += to_copy;
		SvCUR_set(PL_formtarget, SvCUR(PL_formtarget) + to_copy);
		if (tmp)
		    Safefree(tmp);
		break;
	    }

	case FF_0DECIMAL: /* like FF_DECIMAL but for 0### */
	    arg = *fpc++;
	    fmt = (const char *)
		((arg & FORM_NUM_POINT) ? "%#0*.*" NVff : "%0*.*" NVff);
	    goto ff_dec;

	case FF_DECIMAL: /* do @##, ^##, where <arg>=(precision|flags) */
	    arg = *fpc++;
 	    fmt = (const char *)
		((arg & FORM_NUM_POINT) ? "%#*.*" NVff : "%*.*" NVff);
	ff_dec:
	    /* If the field is marked with ^ and the value is undefined,
	       blank it out. */
	    if ((arg & FORM_NUM_BLANK) && !SvOK(sv)) {
		arg = fieldsize;
		while (arg--)
		    *t++ = ' ';
		break;
	    }
	    gotsome = TRUE;
	    value = SvNV(sv);
	    /* overflow evidence */
	    if (num_overflow(value, fieldsize, arg)) {
	        arg = fieldsize;
		while (arg--)
		    *t++ = '#';
		break;
	    }
	    /* Formats aren't yet marked for locales, so assume "yes". */
	    {
                Size_t max = SvLEN(PL_formtarget) - (t - SvPVX(PL_formtarget));
                int len;
                DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                STORE_LC_NUMERIC_SET_TO_NEEDED();
                arg &= ~(FORM_NUM_POINT|FORM_NUM_BLANK);
#ifdef USE_QUADMATH
                {
                    const char* qfmt = quadmath_format_single(fmt);
                    int len;
                    if (!qfmt)
                        Perl_croak_nocontext("panic: quadmath invalid format \"%s\"", fmt);
                    len = quadmath_snprintf(t, max, qfmt, (int) fieldsize, (int) arg, value);
                    if (len == -1)
                        Perl_croak_nocontext("panic: quadmath_snprintf failed, format \"%s\"", qfmt);
                    if (qfmt != fmt)
                        Safefree(fmt);
                }
#else
                /* we generate fmt ourselves so it is safe */
                GCC_DIAG_IGNORE(-Wformat-nonliteral);
                len = my_snprintf(t, max, fmt, (int) fieldsize, (int) arg, value);
                GCC_DIAG_RESTORE;
#endif
                PERL_MY_SNPRINTF_POST_GUARD(len, max);
                RESTORE_LC_NUMERIC();
	    }
	    t += fieldsize;
	    break;

	case FF_NEWLINE: /* delete trailing spaces, then append \n */
	    f++;
	    while (t-- > (SvPVX(PL_formtarget) + linemark) && *t == ' ') ;
	    t++;
	    *t++ = '\n';
	    break;

	case FF_BLANK: /* for arg==0: do '~'; for arg>0 : do '~~' */
	    arg = *fpc++;
	    if (gotsome) {
		if (arg) {		/* repeat until fields exhausted? */
		    fpc--;
		    goto end;
		}
	    }
	    else {
		t = SvPVX(PL_formtarget) + linemark;
		lines--;
	    }
	    break;

	case FF_MORE: /* replace long end of string with '...' */
	    {
		const char *s = chophere;
		const char *send = item + len;
		if (chopspace) {
		    while (isSPACE(*s) && (s < send))
			s++;
		}
		if (s < send) {
		    char *s1;
		    arg = fieldsize - itemsize;
		    if (arg) {
			fieldsize -= arg;
			while (arg-- > 0)
			    *t++ = ' ';
		    }
		    s1 = t - 3;
		    if (strnEQ(s1,"   ",3)) {
			while (s1 > SvPVX_const(PL_formtarget) && isSPACE(s1[-1]))
			    s1--;
		    }
		    *s1++ = '.';
		    *s1++ = '.';
		    *s1++ = '.';
		}
		break;
	    }

	case FF_END: /* tidy up, then return */
	end:
	    assert(t < SvPVX_const(PL_formtarget) + SvLEN(PL_formtarget));
	    *t = '\0';
	    SvCUR_set(PL_formtarget, t - SvPVX_const(PL_formtarget));
	    if (targ_is_utf8)
		SvUTF8_on(PL_formtarget);
	    FmLINES(PL_formtarget) += lines;
	    SP = ORIGMARK;
	    if (fpc[-1] == FF_BLANK)
		RETURNOP(cLISTOP->op_first);
	    else
		RETPUSHYES;
	}
    }
}

/* also used for: pp_mapstart() */
PP(pp_grepstart)
{
    dSP;
    SV *src;

    if (PL_stack_base + TOPMARK == SP) {
	(void)POPMARK;
	if (GIMME_V == G_SCALAR)
	    XPUSHs(&PL_sv_zero);
	RETURNOP(PL_op->op_next->op_next);
    }
    PL_stack_sp = PL_stack_base + TOPMARK + 1;
    Perl_pp_pushmark(aTHX);				/* push dst */
    Perl_pp_pushmark(aTHX);				/* push src */
    ENTER_with_name("grep");					/* enter outer scope */

    SAVETMPS;
    SAVE_DEFSV;
    ENTER_with_name("grep_item");					/* enter inner scope */
    SAVEVPTR(PL_curpm);

    src = PL_stack_base[TOPMARK];
    if (SvPADTMP(src)) {
	src = PL_stack_base[TOPMARK] = sv_mortalcopy(src);
	PL_tmps_floor++;
    }
    SvTEMP_off(src);
    DEFSV_set(src);

    PUTBACK;
    if (PL_op->op_type == OP_MAPSTART)
	Perl_pp_pushmark(aTHX);			/* push top */
    return ((LOGOP*)PL_op->op_next)->op_other;
}

PP(pp_mapwhile)
{
    dSP;
    const U8 gimme = GIMME_V;
    I32 items = (SP - PL_stack_base) - TOPMARK; /* how many new items */
    I32 count;
    I32 shift;
    SV** src;
    SV** dst;

    /* first, move source pointer to the next item in the source list */
    ++PL_markstack_ptr[-1];

    /* if there are new items, push them into the destination list */
    if (items && gimme != G_VOID) {
	/* might need to make room back there first */
	if (items > PL_markstack_ptr[-1] - PL_markstack_ptr[-2]) {
	    /* XXX this implementation is very pessimal because the stack
	     * is repeatedly extended for every set of items.  Is possible
	     * to do this without any stack extension or copying at all
	     * by maintaining a separate list over which the map iterates
	     * (like foreach does). --gsar */

	    /* everything in the stack after the destination list moves
	     * towards the end the stack by the amount of room needed */
	    shift = items - (PL_markstack_ptr[-1] - PL_markstack_ptr[-2]);

	    /* items to shift up (accounting for the moved source pointer) */
	    count = (SP - PL_stack_base) - (PL_markstack_ptr[-1] - 1);

	    /* This optimization is by Ben Tilly and it does
	     * things differently from what Sarathy (gsar)
	     * is describing.  The downside of this optimization is
	     * that leaves "holes" (uninitialized and hopefully unused areas)
	     * to the Perl stack, but on the other hand this
	     * shouldn't be a problem.  If Sarathy's idea gets
	     * implemented, this optimization should become
	     * irrelevant.  --jhi */
            if (shift < count)
                shift = count; /* Avoid shifting too often --Ben Tilly */

	    EXTEND(SP,shift);
	    src = SP;
	    dst = (SP += shift);
	    PL_markstack_ptr[-1] += shift;
	    *PL_markstack_ptr += shift;
	    while (count--)
		*dst-- = *src--;
	}
	/* copy the new items down to the destination list */
	dst = PL_stack_base + (PL_markstack_ptr[-2] += items) - 1;
	if (gimme == G_ARRAY) {
	    /* add returned items to the collection (making mortal copies
	     * if necessary), then clear the current temps stack frame
	     * *except* for those items. We do this splicing the items
	     * into the start of the tmps frame (so some items may be on
	     * the tmps stack twice), then moving PL_tmps_floor above
	     * them, then freeing the frame. That way, the only tmps that
	     * accumulate over iterations are the return values for map.
	     * We have to do to this way so that everything gets correctly
	     * freed if we die during the map.
	     */
	    I32 tmpsbase;
	    I32 i = items;
	    /* make space for the slice */
	    EXTEND_MORTAL(items);
	    tmpsbase = PL_tmps_floor + 1;
	    Move(PL_tmps_stack + tmpsbase,
		 PL_tmps_stack + tmpsbase + items,
		 PL_tmps_ix - PL_tmps_floor,
		 SV*);
	    PL_tmps_ix += items;

	    while (i-- > 0) {
		SV *sv = POPs;
		if (!SvTEMP(sv))
		    sv = sv_mortalcopy(sv);
		*dst-- = sv;
		PL_tmps_stack[tmpsbase++] = SvREFCNT_inc_simple(sv);
	    }
	    /* clear the stack frame except for the items */
	    PL_tmps_floor += items;
	    FREETMPS;
	    /* FREETMPS may have cleared the TEMP flag on some of the items */
	    i = items;
	    while (i-- > 0)
		SvTEMP_on(PL_tmps_stack[--tmpsbase]);
	}
	else {
	    /* scalar context: we don't care about which values map returns
	     * (we use undef here). And so we certainly don't want to do mortal
	     * copies of meaningless values. */
	    while (items-- > 0) {
		(void)POPs;
		*dst-- = &PL_sv_undef;
	    }
	    FREETMPS;
	}
    }
    else {
	FREETMPS;
    }
    LEAVE_with_name("grep_item");					/* exit inner scope */

    /* All done yet? */
    if (PL_markstack_ptr[-1] > TOPMARK) {

	(void)POPMARK;				/* pop top */
	LEAVE_with_name("grep");					/* exit outer scope */
	(void)POPMARK;				/* pop src */
	items = --*PL_markstack_ptr - PL_markstack_ptr[-1];
	(void)POPMARK;				/* pop dst */
	SP = PL_stack_base + POPMARK;		/* pop original mark */
	if (gimme == G_SCALAR) {
		dTARGET;
		XPUSHi(items);
	}
	else if (gimme == G_ARRAY)
	    SP += items;
	RETURN;
    }
    else {
	SV *src;

	ENTER_with_name("grep_item");					/* enter inner scope */
	SAVEVPTR(PL_curpm);

	/* set $_ to the new source item */
	src = PL_stack_base[PL_markstack_ptr[-1]];
	if (SvPADTMP(src)) {
            src = sv_mortalcopy(src);
        }
	SvTEMP_off(src);
	DEFSV_set(src);

	RETURNOP(cLOGOP->op_other);
    }
}

/* Range stuff. */

PP(pp_range)
{
    if (GIMME_V == G_ARRAY)
	return NORMAL;
    if (SvTRUEx(PAD_SV(PL_op->op_targ)))
	return cLOGOP->op_other;
    else
	return NORMAL;
}

PP(pp_flip)
{
    dSP;

    if (GIMME_V == G_ARRAY) {
	RETURNOP(((LOGOP*)cUNOP->op_first)->op_other);
    }
    else {
	dTOPss;
	SV * const targ = PAD_SV(PL_op->op_targ);
	int flip = 0;

	if (PL_op->op_private & OPpFLIP_LINENUM) {
	    if (GvIO(PL_last_in_gv)) {
		flip = SvIV(sv) == (IV)IoLINES(GvIOp(PL_last_in_gv));
	    }
	    else {
		GV * const gv = gv_fetchpvs(".", GV_ADD|GV_NOTQUAL, SVt_PV);
		if (gv && GvSV(gv))
		    flip = SvIV(sv) == SvIV(GvSV(gv));
	    }
	} else {
	    flip = SvTRUE(sv);
	}
	if (flip) {
	    sv_setiv(PAD_SV(cUNOP->op_first->op_targ), 1);
	    if (PL_op->op_flags & OPf_SPECIAL) {
		sv_setiv(targ, 1);
		SETs(targ);
		RETURN;
	    }
	    else {
		sv_setiv(targ, 0);
		SP--;
		RETURNOP(((LOGOP*)cUNOP->op_first)->op_other);
	    }
	}
        SvPVCLEAR(TARG);
	SETs(targ);
	RETURN;
    }
}

/* This code tries to decide if "$left .. $right" should use the
   magical string increment, or if the range is numeric (we make
   an exception for .."0" [#18165]). AMS 20021031. */

#define RANGE_IS_NUMERIC(left,right) ( \
	SvNIOKp(left)  || (SvOK(left)  && !SvPOKp(left))  || \
	SvNIOKp(right) || (SvOK(right) && !SvPOKp(right)) || \
	(((!SvOK(left) && SvOK(right)) || ((!SvOK(left) || \
          looks_like_number(left)) && SvPOKp(left) && *SvPVX_const(left) != '0')) \
         && (!SvOK(right) || looks_like_number(right))))

PP(pp_flop)
{
    dSP;

    if (GIMME_V == G_ARRAY) {
	dPOPPOPssrl;

	SvGETMAGIC(left);
	SvGETMAGIC(right);

	if (RANGE_IS_NUMERIC(left,right)) {
	    IV i, j, n;
	    if ((SvOK(left) && !SvIOK(left) && SvNV_nomg(left) < IV_MIN) ||
		(SvOK(right) && (SvIOK(right)
				 ? SvIsUV(right) && SvUV(right) > IV_MAX
				 : SvNV_nomg(right) > IV_MAX)))
		DIE(aTHX_ "Range iterator outside integer range");
	    i = SvIV_nomg(left);
	    j = SvIV_nomg(right);
	    if (j >= i) {
                /* Dance carefully around signed max. */
                bool overflow = (i <= 0 && j > SSize_t_MAX + i - 1);
                if (!overflow) {
                    n = j - i + 1;
                    /* The wraparound of signed integers is undefined
                     * behavior, but here we aim for count >=1, and
                     * negative count is just wrong. */
                    if (n < 1
#if IVSIZE > Size_t_size
                        || n > SSize_t_MAX
#endif
                        )
                        overflow = TRUE;
                }
                if (overflow)
                    Perl_croak(aTHX_ "Out of memory during list extend");
		EXTEND_MORTAL(n);
		EXTEND(SP, n);
	    }
	    else
		n = 0;
	    while (n--) {
		SV * const sv = sv_2mortal(newSViv(i));
		PUSHs(sv);
                if (n) /* avoid incrementing above IV_MAX */
                    i++;
	    }
	}
	else {
	    STRLEN len, llen;
	    const char * const lpv = SvPV_nomg_const(left, llen);
	    const char * const tmps = SvPV_nomg_const(right, len);

	    SV *sv = newSVpvn_flags(lpv, llen, SvUTF8(left)|SVs_TEMP);
            if (DO_UTF8(right) && IN_UNI_8_BIT)
                len = sv_len_utf8_nomg(right);
	    while (!SvNIOKp(sv) && SvCUR(sv) <= len) {
		XPUSHs(sv);
	        if (strEQ(SvPVX_const(sv),tmps))
	            break;
		sv = sv_2mortal(newSVsv(sv));
		sv_inc(sv);
	    }
	}
    }
    else {
	dTOPss;
	SV * const targ = PAD_SV(cUNOP->op_first->op_targ);
	int flop = 0;
	sv_inc(targ);

	if (PL_op->op_private & OPpFLIP_LINENUM) {
	    if (GvIO(PL_last_in_gv)) {
		flop = SvIV(sv) == (IV)IoLINES(GvIOp(PL_last_in_gv));
	    }
	    else {
		GV * const gv = gv_fetchpvs(".", GV_ADD|GV_NOTQUAL, SVt_PV);
		if (gv && GvSV(gv)) flop = SvIV(sv) == SvIV(GvSV(gv));
	    }
	}
	else {
	    flop = SvTRUE(sv);
	}

	if (flop) {
	    sv_setiv(PAD_SV(((UNOP*)cUNOP->op_first)->op_first->op_targ), 0);
	    sv_catpvs(targ, "E0");
	}
	SETs(targ);
    }

    RETURN;
}

/* Control. */

static const char * const context_name[] = {
    "pseudo-block",
    NULL, /* CXt_WHEN never actually needs "block" */
    NULL, /* CXt_BLOCK never actually needs "block" */
    NULL, /* CXt_GIVEN never actually needs "block" */
    NULL, /* CXt_LOOP_PLAIN never actually needs "loop" */
    NULL, /* CXt_LOOP_LAZYIV never actually needs "loop" */
    NULL, /* CXt_LOOP_LAZYSV never actually needs "loop" */
    NULL, /* CXt_LOOP_LIST never actually needs "loop" */
    NULL, /* CXt_LOOP_ARY never actually needs "loop" */
    "subroutine",
    "format",
    "eval",
    "substitution",
};

STATIC I32
S_dopoptolabel(pTHX_ const char *label, STRLEN len, U32 flags)
{
    I32 i;

    PERL_ARGS_ASSERT_DOPOPTOLABEL;

    for (i = cxstack_ix; i >= 0; i--) {
	const PERL_CONTEXT * const cx = &cxstack[i];
	switch (CxTYPE(cx)) {
	case CXt_SUBST:
	case CXt_SUB:
	case CXt_FORMAT:
	case CXt_EVAL:
	case CXt_NULL:
	    /* diag_listed_as: Exiting subroutine via %s */
	    Perl_ck_warner(aTHX_ packWARN(WARN_EXITING), "Exiting %s via %s",
			   context_name[CxTYPE(cx)], OP_NAME(PL_op));
	    if (CxTYPE(cx) == CXt_NULL) /* sort BLOCK */
		return -1;
	    break;
	case CXt_LOOP_PLAIN:
	case CXt_LOOP_LAZYIV:
	case CXt_LOOP_LAZYSV:
	case CXt_LOOP_LIST:
	case CXt_LOOP_ARY:
	  {
            STRLEN cx_label_len = 0;
            U32 cx_label_flags = 0;
	    const char *cx_label = CxLABEL_len_flags(cx, &cx_label_len, &cx_label_flags);
	    if (!cx_label || !(
                    ( (cx_label_flags & SVf_UTF8) != (flags & SVf_UTF8) ) ?
                        (flags & SVf_UTF8)
                            ? (bytes_cmp_utf8(
                                        (const U8*)cx_label, cx_label_len,
                                        (const U8*)label, len) == 0)
                            : (bytes_cmp_utf8(
                                        (const U8*)label, len,
                                        (const U8*)cx_label, cx_label_len) == 0)
                    : (len == cx_label_len && ((cx_label == label)
                                    || memEQ(cx_label, label, len))) )) {
		DEBUG_l(Perl_deb(aTHX_ "(poptolabel(): skipping label at cx=%ld %s)\n",
			(long)i, cx_label));
		continue;
	    }
	    DEBUG_l( Perl_deb(aTHX_ "(poptolabel(): found label at cx=%ld %s)\n", (long)i, label));
	    return i;
	  }
	}
    }
    return i;
}



U8
Perl_dowantarray(pTHX)
{
    const U8 gimme = block_gimme();
    return (gimme == G_VOID) ? G_SCALAR : gimme;
}

U8
Perl_block_gimme(pTHX)
{
    const I32 cxix = dopoptosub(cxstack_ix);
    U8 gimme;
    if (cxix < 0)
	return G_VOID;

    gimme = (cxstack[cxix].blk_gimme & G_WANT);
    if (!gimme)
	Perl_croak(aTHX_ "panic: bad gimme: %d\n", gimme);
    return gimme;
}


I32
Perl_is_lvalue_sub(pTHX)
{
    const I32 cxix = dopoptosub(cxstack_ix);
    assert(cxix >= 0);  /* We should only be called from inside subs */

    if (CxLVAL(cxstack + cxix) && CvLVALUE(cxstack[cxix].blk_sub.cv))
	return CxLVAL(cxstack + cxix);
    else
	return 0;
}

/* only used by cx_pushsub() */
I32
Perl_was_lvalue_sub(pTHX)
{
    const I32 cxix = dopoptosub(cxstack_ix-1);
    assert(cxix >= 0);  /* We should only be called from inside subs */

    if (CxLVAL(cxstack + cxix) && CvLVALUE(cxstack[cxix].blk_sub.cv))
	return CxLVAL(cxstack + cxix);
    else
	return 0;
}

STATIC I32
S_dopoptosub_at(pTHX_ const PERL_CONTEXT *cxstk, I32 startingblock)
{
    I32 i;

    PERL_ARGS_ASSERT_DOPOPTOSUB_AT;
#ifndef DEBUGGING
    PERL_UNUSED_CONTEXT;
#endif

    for (i = startingblock; i >= 0; i--) {
	const PERL_CONTEXT * const cx = &cxstk[i];
	switch (CxTYPE(cx)) {
	default:
	    continue;
	case CXt_SUB:
            /* in sub foo { /(?{...})/ }, foo ends up on the CX stack
             * twice; the first for the normal foo() call, and the second
             * for a faked up re-entry into the sub to execute the
             * code block. Hide this faked entry from the world. */
            if (cx->cx_type & CXp_SUB_RE_FAKE)
                continue;
            /* FALLTHROUGH */
	case CXt_EVAL:
	case CXt_FORMAT:
	    DEBUG_l( Perl_deb(aTHX_ "(dopoptosub_at(): found sub at cx=%ld)\n", (long)i));
	    return i;
	}
    }
    return i;
}

STATIC I32
S_dopoptoeval(pTHX_ I32 startingblock)
{
    I32 i;
    for (i = startingblock; i >= 0; i--) {
	const PERL_CONTEXT *cx = &cxstack[i];
	switch (CxTYPE(cx)) {
	default:
	    continue;
	case CXt_EVAL:
	    DEBUG_l( Perl_deb(aTHX_ "(dopoptoeval(): found eval at cx=%ld)\n", (long)i));
	    return i;
	}
    }
    return i;
}

STATIC I32
S_dopoptoloop(pTHX_ I32 startingblock)
{
    I32 i;
    for (i = startingblock; i >= 0; i--) {
	const PERL_CONTEXT * const cx = &cxstack[i];
	switch (CxTYPE(cx)) {
	case CXt_SUBST:
	case CXt_SUB:
	case CXt_FORMAT:
	case CXt_EVAL:
	case CXt_NULL:
	    /* diag_listed_as: Exiting subroutine via %s */
	    Perl_ck_warner(aTHX_ packWARN(WARN_EXITING), "Exiting %s via %s",
			   context_name[CxTYPE(cx)], OP_NAME(PL_op));
	    if ((CxTYPE(cx)) == CXt_NULL) /* sort BLOCK */
		return -1;
	    break;
	case CXt_LOOP_PLAIN:
	case CXt_LOOP_LAZYIV:
	case CXt_LOOP_LAZYSV:
	case CXt_LOOP_LIST:
	case CXt_LOOP_ARY:
	    DEBUG_l( Perl_deb(aTHX_ "(dopoptoloop(): found loop at cx=%ld)\n", (long)i));
	    return i;
	}
    }
    return i;
}

/* find the next GIVEN or FOR (with implicit $_) loop context block */

STATIC I32
S_dopoptogivenfor(pTHX_ I32 startingblock)
{
    I32 i;
    for (i = startingblock; i >= 0; i--) {
	const PERL_CONTEXT *cx = &cxstack[i];
	switch (CxTYPE(cx)) {
	default:
	    continue;
	case CXt_GIVEN:
	    DEBUG_l( Perl_deb(aTHX_ "(dopoptogivenfor(): found given at cx=%ld)\n", (long)i));
	    return i;
	case CXt_LOOP_PLAIN:
            assert(!(cx->cx_type & CXp_FOR_DEF));
	    break;
	case CXt_LOOP_LAZYIV:
	case CXt_LOOP_LAZYSV:
	case CXt_LOOP_LIST:
	case CXt_LOOP_ARY:
            if (cx->cx_type & CXp_FOR_DEF) {
		DEBUG_l( Perl_deb(aTHX_ "(dopoptogivenfor(): found foreach at cx=%ld)\n", (long)i));
		return i;
	    }
	}
    }
    return i;
}

STATIC I32
S_dopoptowhen(pTHX_ I32 startingblock)
{
    I32 i;
    for (i = startingblock; i >= 0; i--) {
	const PERL_CONTEXT *cx = &cxstack[i];
	switch (CxTYPE(cx)) {
	default:
	    continue;
	case CXt_WHEN:
	    DEBUG_l( Perl_deb(aTHX_ "(dopoptowhen(): found when at cx=%ld)\n", (long)i));
	    return i;
	}
    }
    return i;
}

/* dounwind(): pop all contexts above (but not including) cxix.
 * Note that it clears the savestack frame associated with each popped
 * context entry, but doesn't free any temps.
 * It does a cx_popblock() of the last frame that it pops, and leaves
 * cxstack_ix equal to cxix.
 */

void
Perl_dounwind(pTHX_ I32 cxix)
{
    if (!PL_curstackinfo) /* can happen if die during thread cloning */
	return;

    while (cxstack_ix > cxix) {
        PERL_CONTEXT *cx = CX_CUR();

	CX_DEBUG(cx, "UNWIND");
	/* Note: we don't need to restore the base context info till the end. */

        CX_LEAVE_SCOPE(cx);

	switch (CxTYPE(cx)) {
	case CXt_SUBST:
	    CX_POPSUBST(cx);
            /* CXt_SUBST is not a block context type, so skip the
             * cx_popblock(cx) below */
            if (cxstack_ix == cxix + 1) {
                cxstack_ix--;
                return;
            }
	    break;
	case CXt_SUB:
	    cx_popsub(cx);
	    break;
	case CXt_EVAL:
	    cx_popeval(cx);
	    break;
	case CXt_LOOP_PLAIN:
	case CXt_LOOP_LAZYIV:
	case CXt_LOOP_LAZYSV:
	case CXt_LOOP_LIST:
	case CXt_LOOP_ARY:
	    cx_poploop(cx);
	    break;
	case CXt_WHEN:
	    cx_popwhen(cx);
	    break;
	case CXt_GIVEN:
	    cx_popgiven(cx);
	    break;
	case CXt_BLOCK:
	case CXt_NULL:
            /* these two don't have a POPFOO() */
	    break;
	case CXt_FORMAT:
	    cx_popformat(cx);
	    break;
	}
        if (cxstack_ix == cxix + 1) {
            cx_popblock(cx);
        }
	cxstack_ix--;
    }

}

void
Perl_qerror(pTHX_ SV *err)
{
    PERL_ARGS_ASSERT_QERROR;

    if (PL_in_eval) {
	if (PL_in_eval & EVAL_KEEPERR) {
		Perl_ck_warner(aTHX_ packWARN(WARN_MISC), "\t(in cleanup) %" SVf,
                                                    SVfARG(err));
	}
	else
	    sv_catsv(ERRSV, err);
    }
    else if (PL_errors)
	sv_catsv(PL_errors, err);
    else
	Perl_warn(aTHX_ "%" SVf, SVfARG(err));
    if (PL_parser)
	++PL_parser->error_count;
}



/* pop a CXt_EVAL context and in addition, if it was a require then
 * based on action:
 *     0: do nothing extra;
 *     1: undef  $INC{$name}; croak "$name did not return a true value";
 *     2: delete $INC{$name}; croak "$errsv: Compilation failed in require"
 */

static void
S_pop_eval_context_maybe_croak(pTHX_ PERL_CONTEXT *cx, SV *errsv, int action)
{
    SV  *namesv = NULL; /* init to avoid dumb compiler warning */
    bool do_croak;

    CX_LEAVE_SCOPE(cx);
    do_croak = action && (CxOLD_OP_TYPE(cx) == OP_REQUIRE);
    if (do_croak) {
        /* keep namesv alive after cx_popeval() */
        namesv = cx->blk_eval.old_namesv;
        cx->blk_eval.old_namesv = NULL;
        sv_2mortal(namesv);
    }
    cx_popeval(cx);
    cx_popblock(cx);
    CX_POP(cx);

    if (do_croak) {
        const char *fmt;
        HV *inc_hv = GvHVn(PL_incgv);
        I32  klen  = SvUTF8(namesv) ? -(I32)SvCUR(namesv) : (I32)SvCUR(namesv);
        const char *key = SvPVX_const(namesv);

        if (action == 1) {
            (void)hv_delete(inc_hv, key, klen, G_DISCARD);
            fmt = "%" SVf " did not return a true value";
            errsv = namesv;
        }
        else {
            (void)hv_store(inc_hv, key, klen, &PL_sv_undef, 0);
            fmt = "%" SVf "Compilation failed in require";
            if (!errsv)
                errsv = newSVpvs_flags("Unknown error\n", SVs_TEMP);
        }

        Perl_croak(aTHX_ fmt, SVfARG(errsv));
    }
}


/* die_unwind(): this is the final destination for the various croak()
 * functions. If we're in an eval, unwind the context and other stacks
 * back to the top-most CXt_EVAL and set $@ to msv; otherwise print msv
 * to STDERR and initiate an exit. Note that if the CXt_EVAL popped back
 * to is a require the exception will be rethrown, as requires don't
 * actually trap exceptions.
 */

void
Perl_die_unwind(pTHX_ SV *msv)
{
    SV *exceptsv = msv;
    U8 in_eval = PL_in_eval;
    PERL_ARGS_ASSERT_DIE_UNWIND;

    if (in_eval) {
	I32 cxix;

        /* We need to keep this SV alive through all the stack unwinding
         * and FREETMPSing below, while ensuing that it doesn't leak
         * if we call out to something which then dies (e.g. sub STORE{die}
         * when unlocalising a tied var). So we do a dance with
         * mortalising and SAVEFREEing.
         */
        sv_2mortal(SvREFCNT_inc_simple_NN(exceptsv));

	/*
	 * Historically, perl used to set ERRSV ($@) early in the die
	 * process and rely on it not getting clobbered during unwinding.
	 * That sucked, because it was liable to get clobbered, so the
	 * setting of ERRSV used to emit the exception from eval{} has
	 * been moved to much later, after unwinding (see just before
	 * JMPENV_JUMP below).	However, some modules were relying on the
	 * early setting, by examining $@ during unwinding to use it as
	 * a flag indicating whether the current unwinding was caused by
	 * an exception.  It was never a reliable flag for that purpose,
	 * being totally open to false positives even without actual
	 * clobberage, but was useful enough for production code to
	 * semantically rely on it.
	 *
	 * We'd like to have a proper introspective interface that
	 * explicitly describes the reason for whatever unwinding
	 * operations are currently in progress, so that those modules
	 * work reliably and $@ isn't further overloaded.  But we don't
	 * have one yet.  In its absence, as a stopgap measure, ERRSV is
	 * now *additionally* set here, before unwinding, to serve as the
	 * (unreliable) flag that it used to.
	 *
	 * This behaviour is temporary, and should be removed when a
	 * proper way to detect exceptional unwinding has been developed.
	 * As of 2010-12, the authors of modules relying on the hack
	 * are aware of the issue, because the modules failed on
	 * perls 5.13.{1..7} which had late setting of $@ without this
	 * early-setting hack.
	 */
	if (!(in_eval & EVAL_KEEPERR))
	    sv_setsv_flags(ERRSV, exceptsv,
                        (SV_GMAGIC|SV_DO_COW_SVSETSV|SV_NOSTEAL));

	if (in_eval & EVAL_KEEPERR) {
	    Perl_ck_warner(aTHX_ packWARN(WARN_MISC), "\t(in cleanup) %" SVf,
			   SVfARG(exceptsv));
	}

	while ((cxix = dopoptoeval(cxstack_ix)) < 0
	       && PL_curstackinfo->si_prev)
	{
	    dounwind(-1);
	    POPSTACK;
	}

	if (cxix >= 0) {
	    PERL_CONTEXT *cx;
	    SV **oldsp;
            U8 gimme;
	    JMPENV *restartjmpenv;
	    OP *restartop;

	    if (cxix < cxstack_ix)
		dounwind(cxix);

            cx = CX_CUR();
            assert(CxTYPE(cx) == CXt_EVAL);

            /* return false to the caller of eval */
            oldsp = PL_stack_base + cx->blk_oldsp;
            gimme = cx->blk_gimme;
	    if (gimme == G_SCALAR)
		*++oldsp = &PL_sv_undef;
	    PL_stack_sp = oldsp;

	    restartjmpenv = cx->blk_eval.cur_top_env;
	    restartop     = cx->blk_eval.retop;

            /* We need a FREETMPS here to avoid late-called destructors
             * clobbering $@ *after* we set it below, e.g.
             *    sub DESTROY { eval { die "X" } }
             *    eval { my $x = bless []; die $x = 0, "Y" };
             *    is($@, "Y")
             * Here the clearing of the $x ref mortalises the anon array,
             * which needs to be freed *before* $& is set to "Y",
             * otherwise it gets overwritten with "X".
             *
             * However, the FREETMPS will clobber exceptsv, so preserve it
             * on the savestack for now.
             */
            SAVEFREESV(SvREFCNT_inc_simple_NN(exceptsv));
            FREETMPS;
            /* now we're about to pop the savestack, so re-mortalise it */
            sv_2mortal(SvREFCNT_inc_simple_NN(exceptsv));

            /* Note that unlike pp_entereval, pp_require isn't supposed to
             * trap errors. So if we're a require, after we pop the
             * CXt_EVAL that pp_require pushed, rethrow the error with
             * croak(exceptsv). This is all handled by the call below when
             * action == 2.
             */
            S_pop_eval_context_maybe_croak(aTHX_ cx, exceptsv, 2);

	    if (!(in_eval & EVAL_KEEPERR))
		sv_setsv(ERRSV, exceptsv);
	    PL_restartjmpenv = restartjmpenv;
	    PL_restartop = restartop;
	    JMPENV_JUMP(3);
	    NOT_REACHED; /* NOTREACHED */
	}
    }

    write_to_stderr(exceptsv);
    my_failure_exit();
    NOT_REACHED; /* NOTREACHED */
}

PP(pp_xor)
{
    dSP; dPOPTOPssrl;
    if (SvTRUE(left) != SvTRUE(right))
	RETSETYES;
    else
	RETSETNO;
}

/*

=head1 CV Manipulation Functions

=for apidoc caller_cx

The XSUB-writer's equivalent of L<caller()|perlfunc/caller>.  The
returned C<PERL_CONTEXT> structure can be interrogated to find all the
information returned to Perl by C<caller>.  Note that XSUBs don't get a
stack frame, so C<caller_cx(0, NULL)> will return information for the
immediately-surrounding Perl code.

This function skips over the automatic calls to C<&DB::sub> made on the
behalf of the debugger.  If the stack frame requested was a sub called by
C<DB::sub>, the return value will be the frame for the call to
C<DB::sub>, since that has the correct line number/etc. for the call
site.  If I<dbcxp> is non-C<NULL>, it will be set to a pointer to the
frame for the sub call itself.

=cut
*/

const PERL_CONTEXT *
Perl_caller_cx(pTHX_ I32 count, const PERL_CONTEXT **dbcxp)
{
    I32 cxix = dopoptosub(cxstack_ix);
    const PERL_CONTEXT *cx;
    const PERL_CONTEXT *ccstack = cxstack;
    const PERL_SI *top_si = PL_curstackinfo;

    for (;;) {
	/* we may be in a higher stacklevel, so dig down deeper */
	while (cxix < 0 && top_si->si_type != PERLSI_MAIN) {
	    top_si = top_si->si_prev;
	    ccstack = top_si->si_cxstack;
	    cxix = dopoptosub_at(ccstack, top_si->si_cxix);
	}
	if (cxix < 0)
	    return NULL;
	/* caller() should not report the automatic calls to &DB::sub */
	if (PL_DBsub && GvCV(PL_DBsub) && cxix >= 0 &&
		ccstack[cxix].blk_sub.cv == GvCV(PL_DBsub))
	    count++;
	if (!count--)
	    break;
	cxix = dopoptosub_at(ccstack, cxix - 1);
    }

    cx = &ccstack[cxix];
    if (dbcxp) *dbcxp = cx;

    if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT) {
        const I32 dbcxix = dopoptosub_at(ccstack, cxix - 1);
	/* We expect that ccstack[dbcxix] is CXt_SUB, anyway, the
	   field below is defined for any cx. */
	/* caller() should not report the automatic calls to &DB::sub */
	if (PL_DBsub && GvCV(PL_DBsub) && dbcxix >= 0 && ccstack[dbcxix].blk_sub.cv == GvCV(PL_DBsub))
	    cx = &ccstack[dbcxix];
    }

    return cx;
}

PP(pp_caller)
{
    dSP;
    const PERL_CONTEXT *cx;
    const PERL_CONTEXT *dbcx;
    U8 gimme = GIMME_V;
    const HEK *stash_hek;
    I32 count = 0;
    bool has_arg = MAXARG && TOPs;
    const COP *lcop;

    if (MAXARG) {
      if (has_arg)
	count = POPi;
      else (void)POPs;
    }

    cx = caller_cx(count + !!(PL_op->op_private & OPpOFFBYONE), &dbcx);
    if (!cx) {
	if (gimme != G_ARRAY) {
	    EXTEND(SP, 1);
	    RETPUSHUNDEF;
	}
	RETURN;
    }

    CX_DEBUG(cx, "CALLER");
    assert(CopSTASH(cx->blk_oldcop));
    stash_hek = SvTYPE(CopSTASH(cx->blk_oldcop)) == SVt_PVHV
      ? HvNAME_HEK((HV*)CopSTASH(cx->blk_oldcop))
      : NULL;
    if (gimme != G_ARRAY) {
        EXTEND(SP, 1);
	if (!stash_hek)
	    PUSHs(&PL_sv_undef);
	else {
	    dTARGET;
	    sv_sethek(TARG, stash_hek);
	    PUSHs(TARG);
	}
	RETURN;
    }

    EXTEND(SP, 11);

    if (!stash_hek)
	PUSHs(&PL_sv_undef);
    else {
	dTARGET;
	sv_sethek(TARG, stash_hek);
	PUSHTARG;
    }
    mPUSHs(newSVpv(OutCopFILE(cx->blk_oldcop), 0));
    lcop = closest_cop(cx->blk_oldcop, OpSIBLING(cx->blk_oldcop),
		       cx->blk_sub.retop, TRUE);
    if (!lcop)
	lcop = cx->blk_oldcop;
    mPUSHu(CopLINE(lcop));
    if (!has_arg)
	RETURN;
    if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT) {
	/* So is ccstack[dbcxix]. */
	if (CvHASGV(dbcx->blk_sub.cv)) {
	    PUSHs(cv_name(dbcx->blk_sub.cv, 0, 0));
	    PUSHs(boolSV(CxHASARGS(cx)));
	}
	else {
	    PUSHs(newSVpvs_flags("(unknown)", SVs_TEMP));
	    PUSHs(boolSV(CxHASARGS(cx)));
	}
    }
    else {
	PUSHs(newSVpvs_flags("(eval)", SVs_TEMP));
	PUSHs(&PL_sv_zero);
    }
    gimme = cx->blk_gimme;
    if (gimme == G_VOID)
	PUSHs(&PL_sv_undef);
    else
	PUSHs(boolSV((gimme & G_WANT) == G_ARRAY));
    if (CxTYPE(cx) == CXt_EVAL) {
	/* eval STRING */
	if (CxOLD_OP_TYPE(cx) == OP_ENTEREVAL) {
            SV *cur_text = cx->blk_eval.cur_text;
            if (SvCUR(cur_text) >= 2) {
                PUSHs(newSVpvn_flags(SvPVX(cur_text), SvCUR(cur_text)-2,
                                     SvUTF8(cur_text)|SVs_TEMP));
            }
            else {
                /* I think this is will always be "", but be sure */
                PUSHs(sv_2mortal(newSVsv(cur_text)));
            }

	    PUSHs(&PL_sv_no);
	}
	/* require */
	else if (cx->blk_eval.old_namesv) {
	    mPUSHs(newSVsv(cx->blk_eval.old_namesv));
	    PUSHs(&PL_sv_yes);
	}
	/* eval BLOCK (try blocks have old_namesv == 0) */
	else {
	    PUSHs(&PL_sv_undef);
	    PUSHs(&PL_sv_undef);
	}
    }
    else {
	PUSHs(&PL_sv_undef);
	PUSHs(&PL_sv_undef);
    }
    if (CxTYPE(cx) == CXt_SUB && CxHASARGS(cx)
	&& CopSTASH_eq(PL_curcop, PL_debstash))
    {
        /* slot 0 of the pad contains the original @_ */
	AV * const ary = MUTABLE_AV(AvARRAY(MUTABLE_AV(
                            PadlistARRAY(CvPADLIST(cx->blk_sub.cv))[
                                cx->blk_sub.olddepth+1]))[0]);
	const SSize_t off = AvARRAY(ary) - AvALLOC(ary);

	Perl_init_dbargs(aTHX);

	if (AvMAX(PL_dbargs) < AvFILLp(ary) + off)
	    av_extend(PL_dbargs, AvFILLp(ary) + off);
	Copy(AvALLOC(ary), AvARRAY(PL_dbargs), AvFILLp(ary) + 1 + off, SV*);
	AvFILLp(PL_dbargs) = AvFILLp(ary) + off;
    }
    mPUSHi(CopHINTS_get(cx->blk_oldcop));
    {
	SV * mask ;
	STRLEN * const old_warnings = cx->blk_oldcop->cop_warnings ;

	if  (old_warnings == pWARN_NONE)
            mask = newSVpvn(WARN_NONEstring, WARNsize) ;
	else if (old_warnings == pWARN_STD && (PL_dowarn & G_WARN_ON) == 0)
            mask = &PL_sv_undef ;
        else if (old_warnings == pWARN_ALL ||
		  (old_warnings == pWARN_STD && PL_dowarn & G_WARN_ON)) {
	    /* Get the bit mask for $warnings::Bits{all}, because
	     * it could have been extended by warnings::register */
	    SV **bits_all;
	    HV * const bits = get_hv("warnings::Bits", 0);
	    if (bits && (bits_all=hv_fetchs(bits, "all", FALSE))) {
		mask = newSVsv(*bits_all);
	    }
	    else {
		mask = newSVpvn(WARN_ALLstring, WARNsize) ;
	    }
	}
        else
            mask = newSVpvn((char *) (old_warnings + 1), old_warnings[0]);
        mPUSHs(mask);
    }

    PUSHs(cx->blk_oldcop->cop_hints_hash ?
	  sv_2mortal(newRV_noinc(MUTABLE_SV(cop_hints_2hv(cx->blk_oldcop, 0))))
	  : &PL_sv_undef);
    RETURN;
}

PP(pp_reset)
{
    dSP;
    const char * tmps;
    STRLEN len = 0;
    if (MAXARG < 1 || (!TOPs && !POPs)) {
        EXTEND(SP, 1);
	tmps = NULL, len = 0;
    }
    else
	tmps = SvPVx_const(POPs, len);
    sv_resetpvn(tmps, len, CopSTASH(PL_curcop));
    PUSHs(&PL_sv_yes);
    RETURN;
}

/* like pp_nextstate, but used instead when the debugger is active */

PP(pp_dbstate)
{
    PL_curcop = (COP*)PL_op;
    TAINT_NOT;		/* Each statement is presumed innocent */
    PL_stack_sp = PL_stack_base + CX_CUR()->blk_oldsp;
    FREETMPS;

    PERL_ASYNC_CHECK();

    if (PL_op->op_flags & OPf_SPECIAL /* breakpoint */
	    || PL_DBsingle_iv || PL_DBsignal_iv || PL_DBtrace_iv)
    {
	dSP;
	PERL_CONTEXT *cx;
	const U8 gimme = G_ARRAY;
	GV * const gv = PL_DBgv;
	CV * cv = NULL;

        if (gv && isGV_with_GP(gv))
            cv = GvCV(gv);

	if (!cv || (!CvROOT(cv) && !CvXSUB(cv)))
	    DIE(aTHX_ "No DB::DB routine defined");

	if (CvDEPTH(cv) >= 1 && !(PL_debug & DEBUG_DB_RECURSE_FLAG))
	    /* don't do recursive DB::DB call */
	    return NORMAL;

	if (CvISXSUB(cv)) {
            ENTER;
            SAVEI32(PL_debug);
            PL_debug = 0;
            SAVESTACK_POS();
            SAVETMPS;
	    PUSHMARK(SP);
	    (void)(*CvXSUB(cv))(aTHX_ cv);
	    FREETMPS;
	    LEAVE;
	    return NORMAL;
	}
	else {
	    cx = cx_pushblock(CXt_SUB, gimme, SP, PL_savestack_ix);
	    cx_pushsub(cx, cv, PL_op->op_next, 0);
            /* OP_DBSTATE's op_private holds hint bits rather than
             * the lvalue-ish flags seen in OP_ENTERSUB. So cancel
             * any CxLVAL() flags that have now been mis-calculated */
            cx->blk_u16 = 0;

            SAVEI32(PL_debug);
            PL_debug = 0;
            SAVESTACK_POS();
	    CvDEPTH(cv)++;
	    if (CvDEPTH(cv) >= 2)
		pad_push(CvPADLIST(cv), CvDEPTH(cv));
	    PAD_SET_CUR_NOSAVE(CvPADLIST(cv), CvDEPTH(cv));
	    RETURNOP(CvSTART(cv));
	}
    }
    else
	return NORMAL;
}


PP(pp_enter)
{
    U8 gimme = GIMME_V;

    (void)cx_pushblock(CXt_BLOCK, gimme, PL_stack_sp, PL_savestack_ix);
    return NORMAL;
}


PP(pp_leave)
{
    PERL_CONTEXT *cx;
    SV **oldsp;
    U8 gimme;

    cx = CX_CUR();
    assert(CxTYPE(cx) == CXt_BLOCK);

    if (PL_op->op_flags & OPf_SPECIAL)
        /* fake block should preserve $1 et al; e.g.  /(...)/ while ...; */
	cx->blk_oldpm = PL_curpm;

    oldsp = PL_stack_base + cx->blk_oldsp;
    gimme = cx->blk_gimme;

    if (gimme == G_VOID)
        PL_stack_sp = oldsp;
    else
        leave_adjust_stacks(oldsp, oldsp, gimme,
                                PL_op->op_private & OPpLVALUE ? 3 : 1);

    CX_LEAVE_SCOPE(cx);
    cx_popblock(cx);
    CX_POP(cx);

    return NORMAL;
}

static bool
S_outside_integer(pTHX_ SV *sv)
{
  if (SvOK(sv)) {
    const NV nv = SvNV_nomg(sv);
    if (Perl_isinfnan(nv))
      return TRUE;
#ifdef NV_PRESERVES_UV
    if (nv < (NV)IV_MIN || nv > (NV)IV_MAX)
      return TRUE;
#else
    if (nv <= (NV)IV_MIN)
      return TRUE;
    if ((nv > 0) &&
        ((nv > (NV)UV_MAX ||
          SvUV_nomg(sv) > (UV)IV_MAX)))
      return TRUE;
#endif
  }
  return FALSE;
}

PP(pp_enteriter)
{
    dSP; dMARK;
    PERL_CONTEXT *cx;
    const U8 gimme = GIMME_V;
    void *itervarp; /* GV or pad slot of the iteration variable */
    SV   *itersave; /* the old var in the iterator var slot */
    U8 cxflags = 0;

    if (PL_op->op_targ) {			 /* "my" variable */
	itervarp = &PAD_SVl(PL_op->op_targ);
        itersave = *(SV**)itervarp;
        assert(itersave);
	if (PL_op->op_private & OPpLVAL_INTRO) {        /* for my $x (...) */
            /* the SV currently in the pad slot is never live during
             * iteration (the slot is always aliased to one of the items)
             * so it's always stale */
	    SvPADSTALE_on(itersave);
	}
        SvREFCNT_inc_simple_void_NN(itersave);
	cxflags = CXp_FOR_PAD;
    }
    else {
	SV * const sv = POPs;
	itervarp = (void *)sv;
        if (LIKELY(isGV(sv))) {		/* symbol table variable */
            itersave = GvSV(sv);
            SvREFCNT_inc_simple_void(itersave);
            cxflags = CXp_FOR_GV;
            if (PL_op->op_private & OPpITER_DEF)
                cxflags |= CXp_FOR_DEF;
        }
        else {                          /* LV ref: for \$foo (...) */
            assert(SvTYPE(sv) == SVt_PVMG);
            assert(SvMAGIC(sv));
            assert(SvMAGIC(sv)->mg_type == PERL_MAGIC_lvref);
            itersave = NULL;
            cxflags = CXp_FOR_LVREF;
        }
    }
    /* OPpITER_DEF (implicit $_) should only occur with a GV iter var */
    assert((cxflags & CXp_FOR_GV) || !(PL_op->op_private & OPpITER_DEF));

    /* Note that this context is initially set as CXt_NULL. Further on
     * down it's changed to one of the CXt_LOOP_*. Before it's changed,
     * there mustn't be anything in the blk_loop substruct that requires
     * freeing or undoing, in case we die in the meantime. And vice-versa.
     */
    cx = cx_pushblock(cxflags, gimme, MARK, PL_savestack_ix);
    cx_pushloop_for(cx, itervarp, itersave);

    if (PL_op->op_flags & OPf_STACKED) {
        /* OPf_STACKED implies either a single array: for(@), with a
         * single AV on the stack, or a range: for (1..5), with 1 and 5 on
         * the stack */
	SV *maybe_ary = POPs;
	if (SvTYPE(maybe_ary) != SVt_PVAV) {
            /* range */
	    dPOPss;
	    SV * const right = maybe_ary;
	    if (UNLIKELY(cxflags & CXp_FOR_LVREF))
		DIE(aTHX_ "Assigned value is not a reference");
	    SvGETMAGIC(sv);
	    SvGETMAGIC(right);
	    if (RANGE_IS_NUMERIC(sv,right)) {
		cx->cx_type |= CXt_LOOP_LAZYIV;
		if (S_outside_integer(aTHX_ sv) ||
                    S_outside_integer(aTHX_ right))
		    DIE(aTHX_ "Range iterator outside integer range");
		cx->blk_loop.state_u.lazyiv.cur = SvIV_nomg(sv);
		cx->blk_loop.state_u.lazyiv.end = SvIV_nomg(right);
	    }
	    else {
		cx->cx_type |= CXt_LOOP_LAZYSV;
		cx->blk_loop.state_u.lazysv.cur = newSVsv(sv);
		cx->blk_loop.state_u.lazysv.end = right;
		SvREFCNT_inc_simple_void_NN(right);
		(void) SvPV_force_nolen(cx->blk_loop.state_u.lazysv.cur);
		/* This will do the upgrade to SVt_PV, and warn if the value
		   is uninitialised.  */
		(void) SvPV_nolen_const(right);
		/* Doing this avoids a check every time in pp_iter in pp_hot.c
		   to replace !SvOK() with a pointer to "".  */
		if (!SvOK(right)) {
		    SvREFCNT_dec(right);
		    cx->blk_loop.state_u.lazysv.end = &PL_sv_no;
		}
	    }
	}
	else /* SvTYPE(maybe_ary) == SVt_PVAV */ {
            /* for (@array) {} */
            cx->cx_type |= CXt_LOOP_ARY;
	    cx->blk_loop.state_u.ary.ary = MUTABLE_AV(maybe_ary);
	    SvREFCNT_inc_simple_void_NN(maybe_ary);
	    cx->blk_loop.state_u.ary.ix =
		(PL_op->op_private & OPpITER_REVERSED) ?
		AvFILL(cx->blk_loop.state_u.ary.ary) + 1 :
		-1;
	}
        /* EXTEND(SP, 1) not needed in this branch because we just did POPs */
    }
    else { /* iterating over items on the stack */
        cx->cx_type |= CXt_LOOP_LIST;
        cx->blk_oldsp = SP - PL_stack_base;
	cx->blk_loop.state_u.stack.basesp = MARK - PL_stack_base;
        cx->blk_loop.state_u.stack.ix =
            (PL_op->op_private & OPpITER_REVERSED)
                ? cx->blk_oldsp + 1
                : cx->blk_loop.state_u.stack.basesp;
        /* pre-extend stack so pp_iter doesn't have to check every time
         * it pushes yes/no */
        EXTEND(SP, 1);
    }

    RETURN;
}

PP(pp_enterloop)
{
    PERL_CONTEXT *cx;
    const U8 gimme = GIMME_V;

    cx = cx_pushblock(CXt_LOOP_PLAIN, gimme, PL_stack_sp, PL_savestack_ix);
    cx_pushloop_plain(cx);
    return NORMAL;
}


PP(pp_leaveloop)
{
    PERL_CONTEXT *cx;
    U8 gimme;
    SV **base;
    SV **oldsp;

    cx = CX_CUR();
    assert(CxTYPE_is_LOOP(cx));
    oldsp = PL_stack_base + cx->blk_oldsp;
    base = CxTYPE(cx) == CXt_LOOP_LIST
                ? PL_stack_base + cx->blk_loop.state_u.stack.basesp
                : oldsp;
    gimme = cx->blk_gimme;

    if (gimme == G_VOID)
        PL_stack_sp = base;
    else
        leave_adjust_stacks(oldsp, base, gimme,
                                PL_op->op_private & OPpLVALUE ? 3 : 1);

    CX_LEAVE_SCOPE(cx);
    cx_poploop(cx);	/* Stack values are safe: release loop vars ... */
    cx_popblock(cx);
    CX_POP(cx);

    return NORMAL;
}


/* This duplicates most of pp_leavesub, but with additional code to handle
 * return args in lvalue context. It was forked from pp_leavesub to
 * avoid slowing down that function any further.
 *
 * Any changes made to this function may need to be copied to pp_leavesub
 * and vice-versa.
 *
 * also tail-called by pp_return
 */

PP(pp_leavesublv)
{
    U8 gimme;
    PERL_CONTEXT *cx;
    SV **oldsp;
    OP *retop;

    cx = CX_CUR();
    assert(CxTYPE(cx) == CXt_SUB);

    if (CxMULTICALL(cx)) {
        /* entry zero of a stack is always PL_sv_undef, which
         * simplifies converting a '()' return into undef in scalar context */
        assert(PL_stack_sp > PL_stack_base || *PL_stack_base == &PL_sv_undef);
	return 0;
    }

    gimme = cx->blk_gimme;
    oldsp = PL_stack_base + cx->blk_oldsp; /* last arg of previous frame */

    if (gimme == G_VOID)
        PL_stack_sp = oldsp;
    else {
        U8   lval    = CxLVAL(cx);
        bool is_lval = (lval && !(lval & OPpENTERSUB_INARGS));
        const char *what = NULL;

        if (gimme == G_SCALAR) {
            if (is_lval) {
                /* check for bad return arg */
                if (oldsp < PL_stack_sp) {
                    SV *sv = *PL_stack_sp;
                    if ((SvPADTMP(sv) || SvREADONLY(sv))) {
                        what =
                            SvREADONLY(sv) ? (sv == &PL_sv_undef) ? "undef"
                            : "a readonly value" : "a temporary";
                    }
                    else goto ok;
                }
                else {
                    /* sub:lvalue{} will take us here. */
                    what = "undef";
                }
              croak:
                Perl_croak(aTHX_
                          "Can't return %s from lvalue subroutine", what);
            }

          ok:
            leave_adjust_stacks(oldsp, oldsp, gimme, is_lval ? 3 : 2);

            if (lval & OPpDEREF) {
                /* lval_sub()->{...} and similar */
                dSP;
                SvGETMAGIC(TOPs);
                if (!SvOK(TOPs)) {
                    TOPs = vivify_ref(TOPs, CxLVAL(cx) & OPpDEREF);
                }
                PUTBACK;
            }
        }
        else {
            assert(gimme == G_ARRAY);
            assert (!(lval & OPpDEREF));

            if (is_lval) {
                /* scan for bad return args */
                SV **p;
                for (p = PL_stack_sp; p > oldsp; p--) {
                    SV *sv = *p;
                    /* the PL_sv_undef exception is to allow things like
                     * this to work, where PL_sv_undef acts as 'skip'
                     * placeholder on the LHS of list assigns:
                     *    sub foo :lvalue { undef }
                     *    ($a, undef, foo(), $b) = 1..4;
                     */
                    if (sv != &PL_sv_undef && (SvPADTMP(sv) || SvREADONLY(sv)))
                    {
                        /* Might be flattened array after $#array =  */
                        what = SvREADONLY(sv)
                                ? "a readonly value" : "a temporary";
                        goto croak;
                    }
                }
            }

            leave_adjust_stacks(oldsp, oldsp, gimme, is_lval ? 3 : 2);
        }
    }

    CX_LEAVE_SCOPE(cx);
    cx_popsub(cx);	/* Stack values are safe: release CV and @_ ... */
    cx_popblock(cx);
    retop =  cx->blk_sub.retop;
    CX_POP(cx);

    return retop;
}


PP(pp_return)
{
    dSP; dMARK;
    PERL_CONTEXT *cx;
    const I32 cxix = dopoptosub(cxstack_ix);

    assert(cxstack_ix >= 0);
    if (cxix < cxstack_ix) {
        if (cxix < 0) {
            if (!(       PL_curstackinfo->si_type == PERLSI_SORT
                  || (   PL_curstackinfo->si_type == PERLSI_MULTICALL
                      && (cxstack[0].cx_type & CXp_SUB_RE_FAKE))
                 )
            )
                DIE(aTHX_ "Can't return outside a subroutine");
            /* We must be in:
             *  a sort block, which is a CXt_NULL not a CXt_SUB;
             *  or a /(?{...})/ block.
             * Handle specially. */
            assert(CxTYPE(&cxstack[0]) == CXt_NULL
                    || (   CxTYPE(&cxstack[0]) == CXt_SUB
                        && (cxstack[0].cx_type & CXp_SUB_RE_FAKE)));
            if (cxstack_ix > 0) {
                /* See comment below about context popping. Since we know
                 * we're scalar and not lvalue, we can preserve the return
                 * value in a simpler fashion than there. */
                SV *sv = *SP;
                assert(cxstack[0].blk_gimme == G_SCALAR);
                if (   (sp != PL_stack_base)
                    && !(SvFLAGS(sv) & (SVs_TEMP|SVs_PADTMP))
                )
                    *SP = sv_mortalcopy(sv);
                dounwind(0);
            }
            /* caller responsible for popping cxstack[0] */
            return 0;
        }

        /* There are contexts that need popping. Doing this may free the
         * return value(s), so preserve them first: e.g. popping the plain
         * loop here would free $x:
         *     sub f {  { my $x = 1; return $x } }
         * We may also need to shift the args down; for example,
         *    for (1,2) { return 3,4 }
         * leaves 1,2,3,4 on the stack. Both these actions will be done by
         * leave_adjust_stacks(), along with freeing any temps. Note that
         * whoever we tail-call (e.g. pp_leaveeval) will also call
         * leave_adjust_stacks(); however, the second call is likely to
         * just see a bunch of SvTEMPs with a ref count of 1, and so just
         * pass them through, rather than copying them again. So this
         * isn't as inefficient as it sounds.
         */
        cx = &cxstack[cxix];
        PUTBACK;
        if (cx->blk_gimme != G_VOID)
            leave_adjust_stacks(MARK, PL_stack_base + cx->blk_oldsp,
                    cx->blk_gimme,
                    CxTYPE(cx) == CXt_SUB && CvLVALUE(cx->blk_sub.cv)
                        ? 3 : 0);
        SPAGAIN;
	dounwind(cxix);
        cx = &cxstack[cxix]; /* CX stack may have been realloced */
    }
    else {
        /* Like in the branch above, we need to handle any extra junk on
         * the stack. But because we're not also popping extra contexts, we
         * don't have to worry about prematurely freeing args. So we just
         * need to do the bare minimum to handle junk, and leave the main
         * arg processing in the function we tail call, e.g. pp_leavesub.
         * In list context we have to splice out the junk; in scalar
         * context we can leave as-is (pp_leavesub will later return the
         * top stack element). But for an  empty arg list, e.g.
         *    for (1,2) { return }
         * we need to set sp = oldsp so that pp_leavesub knows to push
         * &PL_sv_undef onto the stack.
         */
        SV **oldsp;
        cx = &cxstack[cxix];
        oldsp = PL_stack_base + cx->blk_oldsp;
        if (oldsp != MARK) {
            SSize_t nargs = SP - MARK;
            if (nargs) {
                if (cx->blk_gimme == G_ARRAY) {
                    /* shift return args to base of call stack frame */
                    Move(MARK + 1, oldsp + 1, nargs, SV*);
                    PL_stack_sp  = oldsp + nargs;
                }
            }
            else
                PL_stack_sp  = oldsp;
        }
    }

    /* fall through to a normal exit */
    switch (CxTYPE(cx)) {
    case CXt_EVAL:
        return CxTRYBLOCK(cx)
            ? Perl_pp_leavetry(aTHX)
            : Perl_pp_leaveeval(aTHX);
    case CXt_SUB:
        return CvLVALUE(cx->blk_sub.cv)
            ? Perl_pp_leavesublv(aTHX)
            : Perl_pp_leavesub(aTHX);
    case CXt_FORMAT:
        return Perl_pp_leavewrite(aTHX);
    default:
	DIE(aTHX_ "panic: return, type=%u", (unsigned) CxTYPE(cx));
    }
}

/* find the enclosing loop or labelled loop and dounwind() back to it. */

static PERL_CONTEXT *
S_unwind_loop(pTHX)
{
    I32 cxix;
    if (PL_op->op_flags & OPf_SPECIAL) {
	cxix = dopoptoloop(cxstack_ix);
	if (cxix < 0)
	    /* diag_listed_as: Can't "last" outside a loop block */
	    Perl_croak(aTHX_ "Can't \"%s\" outside a loop block",
                OP_NAME(PL_op));
    }
    else {
	dSP;
	STRLEN label_len;
	const char * const label =
	    PL_op->op_flags & OPf_STACKED
		? SvPV(TOPs,label_len)
		: (label_len = strlen(cPVOP->op_pv), cPVOP->op_pv);
	const U32 label_flags =
	    PL_op->op_flags & OPf_STACKED
		? SvUTF8(POPs)
		: (cPVOP->op_private & OPpPV_IS_UTF8) ? SVf_UTF8 : 0;
	PUTBACK;
        cxix = dopoptolabel(label, label_len, label_flags);
	if (cxix < 0)
	    /* diag_listed_as: Label not found for "last %s" */
	    Perl_croak(aTHX_ "Label not found for \"%s %" SVf "\"",
				       OP_NAME(PL_op),
                                       SVfARG(PL_op->op_flags & OPf_STACKED
                                              && !SvGMAGICAL(TOPp1s)
                                              ? TOPp1s
                                              : newSVpvn_flags(label,
                                                    label_len,
                                                    label_flags | SVs_TEMP)));
    }
    if (cxix < cxstack_ix)
	dounwind(cxix);
    return &cxstack[cxix];
}


PP(pp_last)
{
    PERL_CONTEXT *cx;
    OP* nextop;

    cx = S_unwind_loop(aTHX);

    assert(CxTYPE_is_LOOP(cx));
    PL_stack_sp = PL_stack_base
                + (CxTYPE(cx) == CXt_LOOP_LIST
                    ?  cx->blk_loop.state_u.stack.basesp
                    : cx->blk_oldsp
                );

    TAINT_NOT;

    /* Stack values are safe: */
    CX_LEAVE_SCOPE(cx);
    cx_poploop(cx);	/* release loop vars ... */
    cx_popblock(cx);
    nextop = cx->blk_loop.my_op->op_lastop->op_next;
    CX_POP(cx);

    return nextop;
}

PP(pp_next)
{
    PERL_CONTEXT *cx;

    /* if not a bare 'next' in the main scope, search for it */
    cx = CX_CUR();
    if (!((PL_op->op_flags & OPf_SPECIAL) && CxTYPE_is_LOOP(cx)))
        cx = S_unwind_loop(aTHX);

    cx_topblock(cx);
    PL_curcop = cx->blk_oldcop;
    PERL_ASYNC_CHECK();
    return (cx)->blk_loop.my_op->op_nextop;
}

PP(pp_redo)
{
    PERL_CONTEXT *cx = S_unwind_loop(aTHX);
    OP* redo_op = cx->blk_loop.my_op->op_redoop;

    if (redo_op->op_type == OP_ENTER) {
	/* pop one less context to avoid $x being freed in while (my $x..) */
	cxstack_ix++;
        cx = CX_CUR();
	assert(CxTYPE(cx) == CXt_BLOCK);
	redo_op = redo_op->op_next;
    }

    FREETMPS;
    CX_LEAVE_SCOPE(cx);
    cx_topblock(cx);
    PL_curcop = cx->blk_oldcop;
    PERL_ASYNC_CHECK();
    return redo_op;
}

STATIC OP *
S_dofindlabel(pTHX_ OP *o, const char *label, STRLEN len, U32 flags, OP **opstack, OP **oplimit)
{
    OP **ops = opstack;
    static const char* const too_deep = "Target of goto is too deeply nested";

    PERL_ARGS_ASSERT_DOFINDLABEL;

    if (ops >= oplimit)
	Perl_croak(aTHX_ "%s", too_deep);
    if (o->op_type == OP_LEAVE ||
	o->op_type == OP_SCOPE ||
	o->op_type == OP_LEAVELOOP ||
	o->op_type == OP_LEAVESUB ||
	o->op_type == OP_LEAVETRY)
    {
	*ops++ = cUNOPo->op_first;
	if (ops >= oplimit)
	    Perl_croak(aTHX_ "%s", too_deep);
    }
    *ops = 0;
    if (o->op_flags & OPf_KIDS) {
	OP *kid;
	/* First try all the kids at this level, since that's likeliest. */
	for (kid = cUNOPo->op_first; kid; kid = OpSIBLING(kid)) {
	    if (kid->op_type == OP_NEXTSTATE || kid->op_type == OP_DBSTATE) {
                STRLEN kid_label_len;
                U32 kid_label_flags;
		const char *kid_label = CopLABEL_len_flags(kCOP,
                                                    &kid_label_len, &kid_label_flags);
		if (kid_label && (
                    ( (kid_label_flags & SVf_UTF8) != (flags & SVf_UTF8) ) ?
                        (flags & SVf_UTF8)
                            ? (bytes_cmp_utf8(
                                        (const U8*)kid_label, kid_label_len,
                                        (const U8*)label, len) == 0)
                            : (bytes_cmp_utf8(
                                        (const U8*)label, len,
                                        (const U8*)kid_label, kid_label_len) == 0)
                    : ( len == kid_label_len && ((kid_label == label)
                                    || memEQ(kid_label, label, len)))))
		    return kid;
	    }
	}
	for (kid = cUNOPo->op_first; kid; kid = OpSIBLING(kid)) {
	    if (kid == PL_lastgotoprobe)
		continue;
	    if (kid->op_type == OP_NEXTSTATE || kid->op_type == OP_DBSTATE) {
	        if (ops == opstack)
		    *ops++ = kid;
		else if (ops[-1]->op_type == OP_NEXTSTATE ||
		         ops[-1]->op_type == OP_DBSTATE)
		    ops[-1] = kid;
		else
		    *ops++ = kid;
	    }
	    if ((o = dofindlabel(kid, label, len, flags, ops, oplimit)))
		return o;
	}
    }
    *ops = 0;
    return 0;
}


/* also used for: pp_dump() */

PP(pp_goto)
{
    dVAR; dSP;
    OP *retop = NULL;
    I32 ix;
    PERL_CONTEXT *cx;
#define GOTO_DEPTH 64
    OP *enterops[GOTO_DEPTH];
    const char *label = NULL;
    STRLEN label_len = 0;
    U32 label_flags = 0;
    const bool do_dump = (PL_op->op_type == OP_DUMP);
    static const char* const must_have_label = "goto must have label";

    if (PL_op->op_flags & OPf_STACKED) {
        /* goto EXPR  or  goto &foo */

	SV * const sv = POPs;
	SvGETMAGIC(sv);

	if (SvROK(sv) && SvTYPE(SvRV(sv)) == SVt_PVCV) {
            /* This egregious kludge implements goto &subroutine */
	    I32 cxix;
	    PERL_CONTEXT *cx;
	    CV *cv = MUTABLE_CV(SvRV(sv));
	    AV *arg = GvAV(PL_defgv);

	    while (!CvROOT(cv) && !CvXSUB(cv)) {
		const GV * const gv = CvGV(cv);
		if (gv) {
		    GV *autogv;
		    SV *tmpstr;
		    /* autoloaded stub? */
		    if (cv != GvCV(gv) && (cv = GvCV(gv)))
			continue;
		    autogv = gv_autoload_pvn(GvSTASH(gv), GvNAME(gv),
					  GvNAMELEN(gv),
                                          GvNAMEUTF8(gv) ? SVf_UTF8 : 0);
		    if (autogv && (cv = GvCV(autogv)))
			continue;
		    tmpstr = sv_newmortal();
		    gv_efullname3(tmpstr, gv, NULL);
		    DIE(aTHX_ "Goto undefined subroutine &%" SVf, SVfARG(tmpstr));
		}
		DIE(aTHX_ "Goto undefined subroutine");
	    }

	    cxix = dopoptosub(cxstack_ix);
            if (cxix < 0) {
                DIE(aTHX_ "Can't goto subroutine outside a subroutine");
            }
            cx  = &cxstack[cxix];
	    /* ban goto in eval: see <20050521150056.GC20213@iabyn.com> */
	    if (CxTYPE(cx) == CXt_EVAL) {
		if (CxREALEVAL(cx))
		/* diag_listed_as: Can't goto subroutine from an eval-%s */
		    DIE(aTHX_ "Can't goto subroutine from an eval-string");
		else
		/* diag_listed_as: Can't goto subroutine from an eval-%s */
		    DIE(aTHX_ "Can't goto subroutine from an eval-block");
	    }
	    else if (CxMULTICALL(cx))
		DIE(aTHX_ "Can't goto subroutine from a sort sub (or similar callback)");

	    /* First do some returnish stuff. */

	    SvREFCNT_inc_simple_void(cv); /* avoid premature free during unwind */
	    FREETMPS;
	    if (cxix < cxstack_ix) {
		dounwind(cxix);
            }
            cx = CX_CUR();
	    cx_topblock(cx);
	    SPAGAIN;

            /* protect @_ during save stack unwind. */
            if (arg)
                SvREFCNT_inc_NN(sv_2mortal(MUTABLE_SV(arg)));

	    assert(PL_scopestack_ix == cx->blk_oldscopesp);
            CX_LEAVE_SCOPE(cx);

	    if (CxTYPE(cx) == CXt_SUB && CxHASARGS(cx)) {
                /* this is part of cx_popsub_args() */
		AV* av = MUTABLE_AV(PAD_SVl(0));
                assert(AvARRAY(MUTABLE_AV(
                    PadlistARRAY(CvPADLIST(cx->blk_sub.cv))[
                            CvDEPTH(cx->blk_sub.cv)])) == PL_curpad);

                /* we are going to donate the current @_ from the old sub
                 * to the new sub. This first part of the donation puts a
                 * new empty AV in the pad[0] slot of the old sub,
                 * unless pad[0] and @_ differ (e.g. if the old sub did
                 * local *_ = []); in which case clear the old pad[0]
                 * array in the usual way */
		if (av == arg || AvREAL(av))
                    clear_defarray(av, av == arg);
		else CLEAR_ARGARRAY(av);
	    }

            /* don't restore PL_comppad here. It won't be needed if the
             * sub we're going to is non-XS, but restoring it early then
             * croaking (e.g. the "Goto undefined subroutine" below)
             * means the CX block gets processed again in dounwind,
             * but this time with the wrong PL_comppad */

	    /* A destructor called during LEAVE_SCOPE could have undefined
	     * our precious cv.  See bug #99850. */
	    if (!CvROOT(cv) && !CvXSUB(cv)) {
		const GV * const gv = CvGV(cv);
		if (gv) {
		    SV * const tmpstr = sv_newmortal();
		    gv_efullname3(tmpstr, gv, NULL);
		    DIE(aTHX_ "Goto undefined subroutine &%" SVf,
			       SVfARG(tmpstr));
		}
		DIE(aTHX_ "Goto undefined subroutine");
	    }

	    if (CxTYPE(cx) == CXt_SUB) {
		CvDEPTH(cx->blk_sub.cv) = cx->blk_sub.olddepth;
                SvREFCNT_dec_NN(cx->blk_sub.cv);
            }

	    /* Now do some callish stuff. */
	    if (CvISXSUB(cv)) {
		const SSize_t items = arg ? AvFILL(arg) + 1 : 0;
		const bool m = arg ? cBOOL(SvRMAGICAL(arg)) : 0;
		SV** mark;

                ENTER;
                SAVETMPS;
                SAVEFREESV(cv); /* later, undo the 'avoid premature free' hack */

		/* put GvAV(defgv) back onto stack */
		if (items) {
		    EXTEND(SP, items+1); /* @_ could have been extended. */
		}
		mark = SP;
		if (items) {
		    SSize_t index;
		    bool r = cBOOL(AvREAL(arg));
		    for (index=0; index<items; index++)
		    {
			SV *sv;
			if (m) {
			    SV ** const svp = av_fetch(arg, index, 0);
			    sv = svp ? *svp : NULL;
			}
			else sv = AvARRAY(arg)[index];
			SP[index+1] = sv
			    ? r ? SvREFCNT_inc_NN(sv_2mortal(sv)) : sv
			    : sv_2mortal(newSVavdefelem(arg, index, 1));
		    }
		}
		SP += items;
		if (CxTYPE(cx) == CXt_SUB && CxHASARGS(cx)) {
		    /* Restore old @_ */
                    CX_POP_SAVEARRAY(cx);
		}

		retop = cx->blk_sub.retop;
                PL_comppad = cx->blk_sub.prevcomppad;
                PL_curpad = LIKELY(PL_comppad) ? AvARRAY(PL_comppad) : NULL;

		/* XS subs don't have a CXt_SUB, so pop it;
                 * this is a cx_popblock(), less all the stuff we already did
                 * for cx_topblock() earlier */
                PL_curcop = cx->blk_oldcop;
                CX_POP(cx);

		/* Push a mark for the start of arglist */
		PUSHMARK(mark);
		PUTBACK;
		(void)(*CvXSUB(cv))(aTHX_ cv);
		LEAVE;
		goto _return;
	    }
	    else {
		PADLIST * const padlist = CvPADLIST(cv);

                SAVEFREESV(cv); /* later, undo the 'avoid premature free' hack */

                /* partial unrolled cx_pushsub(): */

		cx->blk_sub.cv = cv;
		cx->blk_sub.olddepth = CvDEPTH(cv);

		CvDEPTH(cv)++;
                SvREFCNT_inc_simple_void_NN(cv);
		if (CvDEPTH(cv) > 1) {
		    if (CvDEPTH(cv) == PERL_SUB_DEPTH_WARN && ckWARN(WARN_RECURSION))
			sub_crush_depth(cv);
		    pad_push(padlist, CvDEPTH(cv));
		}
		PL_curcop = cx->blk_oldcop;
		PAD_SET_CUR_NOSAVE(padlist, CvDEPTH(cv));
		if (CxHASARGS(cx))
		{
                    /* second half of donating @_ from the old sub to the
                     * new sub: abandon the original pad[0] AV in the
                     * new sub, and replace it with the donated @_.
                     * pad[0] takes ownership of the extra refcount
                     * we gave arg earlier */
		    if (arg) {
			SvREFCNT_dec(PAD_SVl(0));
			PAD_SVl(0) = (SV *)arg;
                        SvREFCNT_inc_simple_void_NN(arg);
		    }

		    /* GvAV(PL_defgv) might have been modified on scope
		       exit, so point it at arg again. */
		    if (arg != GvAV(PL_defgv)) {
			AV * const av = GvAV(PL_defgv);
			GvAV(PL_defgv) = (AV *)SvREFCNT_inc_simple(arg);
			SvREFCNT_dec(av);
		    }
		}

		if (PERLDB_SUB) {	/* Checking curstash breaks DProf. */
		    Perl_get_db_sub(aTHX_ NULL, cv);
		    if (PERLDB_GOTO) {
			CV * const gotocv = get_cvs("DB::goto", 0);
			if (gotocv) {
			    PUSHMARK( PL_stack_sp );
			    call_sv(MUTABLE_SV(gotocv), G_SCALAR | G_NODEBUG);
			    PL_stack_sp--;
			}
		    }
		}
		retop = CvSTART(cv);
		goto putback_return;
	    }
	}
	else {
            /* goto EXPR */
	    label       = SvPV_nomg_const(sv, label_len);
            label_flags = SvUTF8(sv);
	}
    }
    else if (!(PL_op->op_flags & OPf_SPECIAL)) {
        /* goto LABEL  or  dump LABEL */
 	label       = cPVOP->op_pv;
        label_flags = (cPVOP->op_private & OPpPV_IS_UTF8) ? SVf_UTF8 : 0;
        label_len   = strlen(label);
    }
    if (!(do_dump || label_len)) DIE(aTHX_ "%s", must_have_label);

    PERL_ASYNC_CHECK();

    if (label_len) {
	OP *gotoprobe = NULL;
	bool leaving_eval = FALSE;
	bool in_block = FALSE;
	bool pseudo_block = FALSE;
	PERL_CONTEXT *last_eval_cx = NULL;

	/* find label */

	PL_lastgotoprobe = NULL;
	*enterops = 0;
	for (ix = cxstack_ix; ix >= 0; ix--) {
	    cx = &cxstack[ix];
	    switch (CxTYPE(cx)) {
	    case CXt_EVAL:
		leaving_eval = TRUE;
                if (!CxTRYBLOCK(cx)) {
		    gotoprobe = (last_eval_cx ?
				last_eval_cx->blk_eval.old_eval_root :
				PL_eval_root);
		    last_eval_cx = cx;
		    break;
                }
                /* else fall through */
            case CXt_LOOP_PLAIN:
            case CXt_LOOP_LAZYIV:
            case CXt_LOOP_LAZYSV:
            case CXt_LOOP_LIST:
            case CXt_LOOP_ARY:
	    case CXt_GIVEN:
	    case CXt_WHEN:
		gotoprobe = OpSIBLING(cx->blk_oldcop);
		break;
	    case CXt_SUBST:
		continue;
	    case CXt_BLOCK:
		if (ix) {
		    gotoprobe = OpSIBLING(cx->blk_oldcop);
		    in_block = TRUE;
		} else
		    gotoprobe = PL_main_root;
		break;
	    case CXt_SUB:
		gotoprobe = CvROOT(cx->blk_sub.cv);
		pseudo_block = cBOOL(CxMULTICALL(cx));
		break;
	    case CXt_FORMAT:
	    case CXt_NULL:
		DIE(aTHX_ "Can't \"goto\" out of a pseudo block");
	    default:
		if (ix)
		    DIE(aTHX_ "panic: goto, type=%u, ix=%ld",
			CxTYPE(cx), (long) ix);
		gotoprobe = PL_main_root;
		break;
	    }
	    if (gotoprobe) {
                OP *sibl1, *sibl2;

		retop = dofindlabel(gotoprobe, label, label_len, label_flags,
				    enterops, enterops + GOTO_DEPTH);
		if (retop)
		    break;
		if ( (sibl1 = OpSIBLING(gotoprobe)) &&
		     sibl1->op_type == OP_UNSTACK &&
		     (sibl2 = OpSIBLING(sibl1)))
                {
		    retop = dofindlabel(sibl2,
					label, label_len, label_flags, enterops,
					enterops + GOTO_DEPTH);
		    if (retop)
			break;
		}
	    }
	    if (pseudo_block)
		DIE(aTHX_ "Can't \"goto\" out of a pseudo block");
	    PL_lastgotoprobe = gotoprobe;
	}
	if (!retop)
	    DIE(aTHX_ "Can't find label %" UTF8f,
		       UTF8fARG(label_flags, label_len, label));

	/* if we're leaving an eval, check before we pop any frames
           that we're not going to punt, otherwise the error
	   won't be caught */

	if (leaving_eval && *enterops && enterops[1]) {
	    I32 i;
            for (i = 1; enterops[i]; i++)
                if (enterops[i]->op_type == OP_ENTERITER)
                    DIE(aTHX_ "Can't \"goto\" into the middle of a foreach loop");
	}

	if (*enterops && enterops[1]) {
	    I32 i = enterops[1]->op_type == OP_ENTER && in_block ? 2 : 1;
	    if (enterops[i])
		deprecate("\"goto\" to jump into a construct");
	}

	/* pop unwanted frames */

	if (ix < cxstack_ix) {
	    if (ix < 0)
		DIE(aTHX_ "panic: docatch: illegal ix=%ld", (long)ix);
	    dounwind(ix);
            cx = CX_CUR();
	    cx_topblock(cx);
	}

	/* push wanted frames */

	if (*enterops && enterops[1]) {
	    OP * const oldop = PL_op;
	    ix = enterops[1]->op_type == OP_ENTER && in_block ? 2 : 1;
	    for (; enterops[ix]; ix++) {
		PL_op = enterops[ix];
		/* Eventually we may want to stack the needed arguments
		 * for each op.  For now, we punt on the hard ones. */
		if (PL_op->op_type == OP_ENTERITER)
		    DIE(aTHX_ "Can't \"goto\" into the middle of a foreach loop");
		PL_op->op_ppaddr(aTHX);
	    }
	    PL_op = oldop;
	}
    }

    if (do_dump) {
#ifdef VMS
	if (!retop) retop = PL_main_start;
#endif
	PL_restartop = retop;
	PL_do_undump = TRUE;

	my_unexec();

	PL_restartop = 0;		/* hmm, must be GNU unexec().. */
	PL_do_undump = FALSE;
    }

    putback_return:
    PL_stack_sp = sp;
    _return:
    PERL_ASYNC_CHECK();
    return retop;
}

PP(pp_exit)
{
    dSP;
    I32 anum;

    if (MAXARG < 1)
	anum = 0;
    else if (!TOPs) {
	anum = 0; (void)POPs;
    }
    else {
	anum = SvIVx(POPs);
#ifdef VMS
	if (anum == 1
	 && SvTRUE(cop_hints_fetch_pvs(PL_curcop, "vmsish_exit", 0)))
	    anum = 0;
        VMSISH_HUSHED  =
            VMSISH_HUSHED || (PL_curcop->op_private & OPpHUSH_VMSISH);
#endif
    }
    PL_exit_flags |= PERL_EXIT_EXPECTED;
    my_exit(anum);
    PUSHs(&PL_sv_undef);
    RETURN;
}

/* Eval. */

STATIC void
S_save_lines(pTHX_ AV *array, SV *sv)
{
    const char *s = SvPVX_const(sv);
    const char * const send = SvPVX_const(sv) + SvCUR(sv);
    I32 line = 1;

    PERL_ARGS_ASSERT_SAVE_LINES;

    while (s && s < send) {
	const char *t;
	SV * const tmpstr = newSV_type(SVt_PVMG);

	t = (const char *)memchr(s, '\n', send - s);
	if (t)
	    t++;
	else
	    t = send;

	sv_setpvn(tmpstr, s, t - s);
	av_store(array, line++, tmpstr);
	s = t;
    }
}

/*
=for apidoc docatch

Check for the cases 0 or 3 of cur_env.je_ret, only used inside an eval context.

0 is used as continue inside eval,

3 is used for a die caught by an inner eval - continue inner loop

See F<cop.h>: je_mustcatch, when set at any runlevel to TRUE, means eval ops must
establish a local jmpenv to handle exception traps.

=cut
*/
STATIC OP *
S_docatch(pTHX_ Perl_ppaddr_t firstpp)
{
    int ret;
    OP * const oldop = PL_op;
    dJMPENV;

    assert(CATCH_GET == TRUE);

    JMPENV_PUSH(ret);
    switch (ret) {
    case 0:
	PL_op = firstpp(aTHX);
 redo_body:
	CALLRUNOPS(aTHX);
	break;
    case 3:
	/* die caught by an inner eval - continue inner loop */
	if (PL_restartop && PL_restartjmpenv == PL_top_env) {
	    PL_restartjmpenv = NULL;
	    PL_op = PL_restartop;
	    PL_restartop = 0;
	    goto redo_body;
	}
	/* FALLTHROUGH */
    default:
	JMPENV_POP;
	PL_op = oldop;
	JMPENV_JUMP(ret);
	NOT_REACHED; /* NOTREACHED */
    }
    JMPENV_POP;
    PL_op = oldop;
    return NULL;
}


/*
=for apidoc find_runcv

Locate the CV corresponding to the currently executing sub or eval.
If C<db_seqp> is non_null, skip CVs that are in the DB package and populate
C<*db_seqp> with the cop sequence number at the point that the DB:: code was
entered.  (This allows debuggers to eval in the scope of the breakpoint
rather than in the scope of the debugger itself.)

=cut
*/

CV*
Perl_find_runcv(pTHX_ U32 *db_seqp)
{
    return Perl_find_runcv_where(aTHX_ 0, 0, db_seqp);
}

/* If this becomes part of the API, it might need a better name. */
CV *
Perl_find_runcv_where(pTHX_ U8 cond, IV arg, U32 *db_seqp)
{
    PERL_SI	 *si;
    int		 level = 0;

    if (db_seqp)
	*db_seqp =
            PL_curcop == &PL_compiling
                ? PL_cop_seqmax
                : PL_curcop->cop_seq;

    for (si = PL_curstackinfo; si; si = si->si_prev) {
        I32 ix;
	for (ix = si->si_cxix; ix >= 0; ix--) {
	    const PERL_CONTEXT *cx = &(si->si_cxstack[ix]);
	    CV *cv = NULL;
	    if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT) {
		cv = cx->blk_sub.cv;
		/* skip DB:: code */
		if (db_seqp && PL_debstash && CvSTASH(cv) == PL_debstash) {
		    *db_seqp = cx->blk_oldcop->cop_seq;
		    continue;
		}
                if (cx->cx_type & CXp_SUB_RE)
                    continue;
	    }
	    else if (CxTYPE(cx) == CXt_EVAL && !CxTRYBLOCK(cx))
		cv = cx->blk_eval.cv;
	    if (cv) {
		switch (cond) {
		case FIND_RUNCV_padid_eq:
		    if (!CvPADLIST(cv)
		     || CvPADLIST(cv)->xpadl_id != (U32)arg)
			continue;
		    return cv;
		case FIND_RUNCV_level_eq:
		    if (level++ != arg) continue;
		    /* GERONIMO! */
		default:
		    return cv;
		}
	    }
	}
    }
    return cond == FIND_RUNCV_padid_eq ? NULL : PL_main_cv;
}


/* Run yyparse() in a setjmp wrapper. Returns:
 *   0: yyparse() successful
 *   1: yyparse() failed
 *   3: yyparse() died
 */
STATIC int
S_try_yyparse(pTHX_ int gramtype)
{
    int ret;
    dJMPENV;

    assert(CxTYPE(CX_CUR()) == CXt_EVAL);
    JMPENV_PUSH(ret);
    switch (ret) {
    case 0:
	ret = yyparse(gramtype) ? 1 : 0;
	break;
    case 3:
	break;
    default:
	JMPENV_POP;
	JMPENV_JUMP(ret);
	NOT_REACHED; /* NOTREACHED */
    }
    JMPENV_POP;
    return ret;
}


/* Compile a require/do or an eval ''.
 *
 * outside is the lexically enclosing CV (if any) that invoked us.
 * seq     is the current COP scope value.
 * hh      is the saved hints hash, if any.
 *
 * Returns a bool indicating whether the compile was successful; if so,
 * PL_eval_start contains the first op of the compiled code; otherwise,
 * pushes undef.
 *
 * This function is called from two places: pp_require and pp_entereval.
 * These can be distinguished by whether PL_op is entereval.
 */

STATIC bool
S_doeval_compile(pTHX_ U8 gimme, CV* outside, U32 seq, HV *hh)
{
    dSP;
    OP * const saveop = PL_op;
    bool clear_hints = saveop->op_type != OP_ENTEREVAL;
    COP * const oldcurcop = PL_curcop;
    bool in_require = (saveop->op_type == OP_REQUIRE);
    int yystatus;
    CV *evalcv;

    PL_in_eval = (in_require
		  ? (EVAL_INREQUIRE | (PL_in_eval & EVAL_INEVAL))
		  : (EVAL_INEVAL |
                        ((PL_op->op_private & OPpEVAL_RE_REPARSING)
                            ? EVAL_RE_REPARSING : 0)));

    PUSHMARK(SP);

    evalcv = MUTABLE_CV(newSV_type(SVt_PVCV));
    CvEVAL_on(evalcv);
    assert(CxTYPE(CX_CUR()) == CXt_EVAL);
    CX_CUR()->blk_eval.cv = evalcv;
    CX_CUR()->blk_gimme = gimme;

    CvOUTSIDE_SEQ(evalcv) = seq;
    CvOUTSIDE(evalcv) = MUTABLE_CV(SvREFCNT_inc_simple(outside));

    /* set up a scratch pad */

    CvPADLIST_set(evalcv, pad_new(padnew_SAVE));
    PL_op = NULL; /* avoid PL_op and PL_curpad referring to different CVs */


    SAVEMORTALIZESV(evalcv);	/* must remain until end of current statement */

    /* make sure we compile in the right package */

    if (CopSTASH_ne(PL_curcop, PL_curstash)) {
	SAVEGENERICSV(PL_curstash);
	PL_curstash = (HV *)CopSTASH(PL_curcop);
	if (SvTYPE(PL_curstash) != SVt_PVHV) PL_curstash = NULL;
	else SvREFCNT_inc_simple_void(PL_curstash);
    }
    /* XXX:ajgo do we really need to alloc an AV for begin/checkunit */
    SAVESPTR(PL_beginav);
    PL_beginav = newAV();
    SAVEFREESV(PL_beginav);
    SAVESPTR(PL_unitcheckav);
    PL_unitcheckav = newAV();