[perl5.git] / sv.c

/*    sv.c
 *
 *    Copyright (c) 1991-1999, Larry Wall
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 */

/*
 * "I wonder what the Entish is for 'yes' and 'no'," he thought.
 */

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

#define FCALL *f
#define SV_CHECK_THINKFIRST(sv) if (SvTHINKFIRST(sv)) sv_force_normal(sv)

static void do_report_used(pTHXo_ SV *sv);
static void do_clean_objs(pTHXo_ SV *sv);
#ifndef DISABLE_DESTRUCTOR_KLUDGE
static void do_clean_named_objs(pTHXo_ SV *sv);
#endif
static void do_clean_all(pTHXo_ SV *sv);


#ifdef PURIFY

#define new_SV(p) \
    STMT_START {					\
	LOCK_SV_MUTEX;					\
	(p) = (SV*)safemalloc(sizeof(SV));		\
	reg_add(p);					\
	UNLOCK_SV_MUTEX;				\
	SvANY(p) = 0;					\
	SvREFCNT(p) = 1;				\
	SvFLAGS(p) = 0;					\
    } STMT_END

#define del_SV(p) \
    STMT_START {					\
	LOCK_SV_MUTEX;					\
	reg_remove(p);					\
        Safefree((char*)(p));				\
	UNLOCK_SV_MUTEX;				\
    } STMT_END

static SV **registry;
static I32 registry_size;

#define REGHASH(sv,size)  ((((U32)(sv)) >> 2) % (size))

#define REG_REPLACE(sv,a,b) \
    STMT_START {					\
	void* p = sv->sv_any;				\
	I32 h = REGHASH(sv, registry_size);		\
	I32 i = h;					\
	while (registry[i] != (a)) {			\
	    if (++i >= registry_size)			\
		i = 0;					\
	    if (i == h)					\
		Perl_die(aTHX_ "SV registry bug");			\
	}						\
	registry[i] = (b);				\
    } STMT_END

#define REG_ADD(sv)	REG_REPLACE(sv,Nullsv,sv)
#define REG_REMOVE(sv)	REG_REPLACE(sv,sv,Nullsv)

STATIC void
S_reg_add(pTHX_ SV *sv)
{
    if (PL_sv_count >= (registry_size >> 1))
    {
	SV **oldreg = registry;
	I32 oldsize = registry_size;

	registry_size = registry_size ? ((registry_size << 2) + 1) : 2037;
	Newz(707, registry, registry_size, SV*);

	if (oldreg) {
	    I32 i;

	    for (i = 0; i < oldsize; ++i) {
		SV* oldsv = oldreg[i];
		if (oldsv)
		    REG_ADD(oldsv);
	    }
	    Safefree(oldreg);
	}
    }

    REG_ADD(sv);
    ++PL_sv_count;
}

STATIC void
S_reg_remove(pTHX_ SV *sv)
{
    REG_REMOVE(sv);
    --PL_sv_count;
}

STATIC void
S_visit(pTHX_ SVFUNC_t f)
{
    I32 i;

    for (i = 0; i < registry_size; ++i) {
	SV* sv = registry[i];
	if (sv && SvTYPE(sv) != SVTYPEMASK)
	    (*f)(sv);
    }
}

void
Perl_sv_add_arena(pTHX_ char *ptr, U32 size, U32 flags)
{
    if (!(flags & SVf_FAKE))
	Safefree(ptr);
}

#else /* ! PURIFY */

/*
 * "A time to plant, and a time to uproot what was planted..."
 */

#define plant_SV(p) \
    STMT_START {					\
	SvANY(p) = (void *)PL_sv_root;			\
	SvFLAGS(p) = SVTYPEMASK;			\
	PL_sv_root = (p);				\
	--PL_sv_count;					\
    } STMT_END

/* sv_mutex must be held while calling uproot_SV() */
#define uproot_SV(p) \
    STMT_START {					\
	(p) = PL_sv_root;				\
	PL_sv_root = (SV*)SvANY(p);			\
	++PL_sv_count;					\
    } STMT_END

#define new_SV(p) \
    STMT_START {					\
	LOCK_SV_MUTEX;					\
	if (PL_sv_root)					\
	    uproot_SV(p);				\
	else						\
	    (p) = more_sv();				\
	UNLOCK_SV_MUTEX;				\
	SvANY(p) = 0;					\
	SvREFCNT(p) = 1;				\
	SvFLAGS(p) = 0;					\
    } STMT_END

#ifdef DEBUGGING

#define del_SV(p) \
    STMT_START {					\
	LOCK_SV_MUTEX;					\
	if (PL_debug & 32768)				\
	    del_sv(p);					\
	else						\
	    plant_SV(p);				\
	UNLOCK_SV_MUTEX;				\
    } STMT_END

STATIC void
S_del_sv(pTHX_ SV *p)
{
    if (PL_debug & 32768) {
	SV* sva;
	SV* sv;
	SV* svend;
	int ok = 0;
	for (sva = PL_sv_arenaroot; sva; sva = (SV *) SvANY(sva)) {
	    sv = sva + 1;
	    svend = &sva[SvREFCNT(sva)];
	    if (p >= sv && p < svend)
		ok = 1;
	}
	if (!ok) {
	    if (ckWARN_d(WARN_INTERNAL))	
	        Perl_warner(aTHX_ WARN_INTERNAL,
		       "Attempt to free non-arena SV: 0x%lx", (unsigned long)p);
	    return;
	}
    }
    plant_SV(p);
}

#else /* ! DEBUGGING */

#define del_SV(p)   plant_SV(p)

#endif /* DEBUGGING */

void
Perl_sv_add_arena(pTHX_ char *ptr, U32 size, U32 flags)
{
    SV* sva = (SV*)ptr;
    register SV* sv;
    register SV* svend;
    Zero(sva, size, char);

    /* The first SV in an arena isn't an SV. */
    SvANY(sva) = (void *) PL_sv_arenaroot;		/* ptr to next arena */
    SvREFCNT(sva) = size / sizeof(SV);		/* number of SV slots */
    SvFLAGS(sva) = flags;			/* FAKE if not to be freed */

    PL_sv_arenaroot = sva;
    PL_sv_root = sva + 1;

    svend = &sva[SvREFCNT(sva) - 1];
    sv = sva + 1;
    while (sv < svend) {
	SvANY(sv) = (void *)(SV*)(sv + 1);
	SvFLAGS(sv) = SVTYPEMASK;
	sv++;
    }
    SvANY(sv) = 0;
    SvFLAGS(sv) = SVTYPEMASK;
}

/* sv_mutex must be held while calling more_sv() */
STATIC SV*
S_more_sv(pTHX)
{
    register SV* sv;

    if (PL_nice_chunk) {
	sv_add_arena(PL_nice_chunk, PL_nice_chunk_size, 0);
	PL_nice_chunk = Nullch;
    }
    else {
	char *chunk;                /* must use New here to match call to */
	New(704,chunk,1008,char);   /* Safefree() in sv_free_arenas()     */
	sv_add_arena(chunk, 1008, 0);
    }
    uproot_SV(sv);
    return sv;
}

STATIC void
S_visit(pTHX_ SVFUNC_t f)
{
    SV* sva;
    SV* sv;
    register SV* svend;

    for (sva = PL_sv_arenaroot; sva; sva = (SV*)SvANY(sva)) {
	svend = &sva[SvREFCNT(sva)];
	for (sv = sva + 1; sv < svend; ++sv) {
	    if (SvTYPE(sv) != SVTYPEMASK)
		(FCALL)(aTHXo_ sv);
	}
    }
}

#endif /* PURIFY */

void
Perl_sv_report_used(pTHX)
{
    visit(do_report_used);
}

void
Perl_sv_clean_objs(pTHX)
{
    PL_in_clean_objs = TRUE;
    visit(do_clean_objs);
#ifndef DISABLE_DESTRUCTOR_KLUDGE
    /* some barnacles may yet remain, clinging to typeglobs */
    visit(do_clean_named_objs);
#endif
    PL_in_clean_objs = FALSE;
}

void
Perl_sv_clean_all(pTHX)
{
    PL_in_clean_all = TRUE;
    visit(do_clean_all);
    PL_in_clean_all = FALSE;
}

void
Perl_sv_free_arenas(pTHX)
{
    SV* sva;
    SV* svanext;

    /* Free arenas here, but be careful about fake ones.  (We assume
       contiguity of the fake ones with the corresponding real ones.) */

    for (sva = PL_sv_arenaroot; sva; sva = svanext) {
	svanext = (SV*) SvANY(sva);
	while (svanext && SvFAKE(svanext))
	    svanext = (SV*) SvANY(svanext);

	if (!SvFAKE(sva))
	    Safefree((void *)sva);
    }

    if (PL_nice_chunk)
	Safefree(PL_nice_chunk);
    PL_nice_chunk = Nullch;
    PL_nice_chunk_size = 0;
    PL_sv_arenaroot = 0;
    PL_sv_root = 0;
}

STATIC XPVIV*
S_new_xiv(pTHX)
{
    IV* xiv;
    LOCK_SV_MUTEX;
    if (!PL_xiv_root)
	more_xiv();
    xiv = PL_xiv_root;
    /*
     * See comment in more_xiv() -- RAM.
     */
    PL_xiv_root = *(IV**)xiv;
    UNLOCK_SV_MUTEX;
    return (XPVIV*)((char*)xiv - STRUCT_OFFSET(XPVIV, xiv_iv));
}

STATIC void
S_del_xiv(pTHX_ XPVIV *p)
{
    IV* xiv = (IV*)((char*)(p) + STRUCT_OFFSET(XPVIV, xiv_iv));
    LOCK_SV_MUTEX;
    *(IV**)xiv = PL_xiv_root;
    PL_xiv_root = xiv;
    UNLOCK_SV_MUTEX;
}

STATIC void
S_more_xiv(pTHX)
{
    register IV* xiv;
    register IV* xivend;
    XPV* ptr;
    New(705, ptr, 1008/sizeof(XPV), XPV);
    ptr->xpv_pv = (char*)PL_xiv_arenaroot;		/* linked list of xiv arenas */
    PL_xiv_arenaroot = ptr;			/* to keep Purify happy */

    xiv = (IV*) ptr;
    xivend = &xiv[1008 / sizeof(IV) - 1];
    xiv += (sizeof(XPV) - 1) / sizeof(IV) + 1;   /* fudge by size of XPV */
    PL_xiv_root = xiv;
    while (xiv < xivend) {
	*(IV**)xiv = (IV *)(xiv + 1);
	xiv++;
    }
    *(IV**)xiv = 0;
}

STATIC XPVNV*
S_new_xnv(pTHX)
{
    NV* xnv;
    LOCK_SV_MUTEX;
    if (!PL_xnv_root)
	more_xnv();
    xnv = PL_xnv_root;
    PL_xnv_root = *(NV**)xnv;
    UNLOCK_SV_MUTEX;
    return (XPVNV*)((char*)xnv - STRUCT_OFFSET(XPVNV, xnv_nv));
}

STATIC void
S_del_xnv(pTHX_ XPVNV *p)
{
    NV* xnv = (NV*)((char*)(p) + STRUCT_OFFSET(XPVNV, xnv_nv));
    LOCK_SV_MUTEX;
    *(NV**)xnv = PL_xnv_root;
    PL_xnv_root = xnv;
    UNLOCK_SV_MUTEX;
}

STATIC void
S_more_xnv(pTHX)
{
    register NV* xnv;
    register NV* xnvend;
    New(711, xnv, 1008/sizeof(NV), NV);
    xnvend = &xnv[1008 / sizeof(NV) - 1];
    xnv += (sizeof(XPVIV) - 1) / sizeof(NV) + 1; /* fudge by sizeof XPVIV */
    PL_xnv_root = xnv;
    while (xnv < xnvend) {
	*(NV**)xnv = (NV*)(xnv + 1);
	xnv++;
    }
    *(NV**)xnv = 0;
}

STATIC XRV*
S_new_xrv(pTHX)
{
    XRV* xrv;
    LOCK_SV_MUTEX;
    if (!PL_xrv_root)
	more_xrv();
    xrv = PL_xrv_root;
    PL_xrv_root = (XRV*)xrv->xrv_rv;
    UNLOCK_SV_MUTEX;
    return xrv;
}

STATIC void
S_del_xrv(pTHX_ XRV *p)
{
    LOCK_SV_MUTEX;
    p->xrv_rv = (SV*)PL_xrv_root;
    PL_xrv_root = p;
    UNLOCK_SV_MUTEX;
}

STATIC void
S_more_xrv(pTHX)
{
    register XRV* xrv;
    register XRV* xrvend;
    New(712, PL_xrv_root, 1008/sizeof(XRV), XRV);
    xrv = PL_xrv_root;
    xrvend = &xrv[1008 / sizeof(XRV) - 1];
    while (xrv < xrvend) {
	xrv->xrv_rv = (SV*)(xrv + 1);
	xrv++;
    }
    xrv->xrv_rv = 0;
}

STATIC XPV*
S_new_xpv(pTHX)
{
    XPV* xpv;
    LOCK_SV_MUTEX;
    if (!PL_xpv_root)
	more_xpv();
    xpv = PL_xpv_root;
    PL_xpv_root = (XPV*)xpv->xpv_pv;
    UNLOCK_SV_MUTEX;
    return xpv;
}

STATIC void
S_del_xpv(pTHX_ XPV *p)
{
    LOCK_SV_MUTEX;
    p->xpv_pv = (char*)PL_xpv_root;
    PL_xpv_root = p;
    UNLOCK_SV_MUTEX;
}

STATIC void
S_more_xpv(pTHX)
{
    register XPV* xpv;
    register XPV* xpvend;
    New(713, PL_xpv_root, 1008/sizeof(XPV), XPV);
    xpv = PL_xpv_root;
    xpvend = &xpv[1008 / sizeof(XPV) - 1];
    while (xpv < xpvend) {
	xpv->xpv_pv = (char*)(xpv + 1);
	xpv++;
    }
    xpv->xpv_pv = 0;
}

#ifdef PURIFY
#define new_XIV() (void*)safemalloc(sizeof(XPVIV))
#define del_XIV(p) Safefree((char*)p)
#else
#define new_XIV() (void*)new_xiv()
#define del_XIV(p) del_xiv((XPVIV*) p)
#endif

#ifdef PURIFY
#define new_XNV() (void*)safemalloc(sizeof(XPVNV))
#define del_XNV(p) Safefree((char*)p)
#else
#define new_XNV() (void*)new_xnv()
#define del_XNV(p) del_xnv((XPVNV*) p)
#endif

#ifdef PURIFY
#define new_XRV() (void*)safemalloc(sizeof(XRV))
#define del_XRV(p) Safefree((char*)p)
#else
#define new_XRV() (void*)new_xrv()
#define del_XRV(p) del_xrv((XRV*) p)
#endif

#ifdef PURIFY
#define new_XPV() (void*)safemalloc(sizeof(XPV))
#define del_XPV(p) Safefree((char*)p)
#else
#define new_XPV() (void*)new_xpv()
#define del_XPV(p) del_xpv((XPV *)p)
#endif

#ifdef PURIFY
#  define my_safemalloc(s) safemalloc(s)
#  define my_safefree(s) safefree(s)
#else
STATIC void* 
S_my_safemalloc(MEM_SIZE size)
{
    char *p;
    New(717, p, size, char);
    return (void*)p;
}
#  define my_safefree(s) Safefree(s)
#endif 

#define new_XPVIV() (void*)my_safemalloc(sizeof(XPVIV))
#define del_XPVIV(p) my_safefree((char*)p)
  
#define new_XPVNV() (void*)my_safemalloc(sizeof(XPVNV))
#define del_XPVNV(p) my_safefree((char*)p)
  
#define new_XPVMG() (void*)my_safemalloc(sizeof(XPVMG))
#define del_XPVMG(p) my_safefree((char*)p)
  
#define new_XPVLV() (void*)my_safemalloc(sizeof(XPVLV))
#define del_XPVLV(p) my_safefree((char*)p)
  
#define new_XPVAV() (void*)my_safemalloc(sizeof(XPVAV))
#define del_XPVAV(p) my_safefree((char*)p)
  
#define new_XPVHV() (void*)my_safemalloc(sizeof(XPVHV))
#define del_XPVHV(p) my_safefree((char*)p)
  
#define new_XPVCV() (void*)my_safemalloc(sizeof(XPVCV))
#define del_XPVCV(p) my_safefree((char*)p)
  
#define new_XPVGV() (void*)my_safemalloc(sizeof(XPVGV))
#define del_XPVGV(p) my_safefree((char*)p)
  
#define new_XPVBM() (void*)my_safemalloc(sizeof(XPVBM))
#define del_XPVBM(p) my_safefree((char*)p)
  
#define new_XPVFM() (void*)my_safemalloc(sizeof(XPVFM))
#define del_XPVFM(p) my_safefree((char*)p)
  
#define new_XPVIO() (void*)my_safemalloc(sizeof(XPVIO))
#define del_XPVIO(p) my_safefree((char*)p)

bool
Perl_sv_upgrade(pTHX_ register SV *sv, U32 mt)
{
    char*	pv;
    U32		cur;
    U32		len;
    IV		iv;
    NV		nv;
    MAGIC*	magic;
    HV*		stash;

    if (SvTYPE(sv) == mt)
	return TRUE;

    if (mt < SVt_PVIV)
	(void)SvOOK_off(sv);

    switch (SvTYPE(sv)) {
    case SVt_NULL:
	pv	= 0;
	cur	= 0;
	len	= 0;
	iv	= 0;
	nv	= 0.0;
	magic	= 0;
	stash	= 0;
	break;
    case SVt_IV:
	pv	= 0;
	cur	= 0;
	len	= 0;
	iv	= SvIVX(sv);
	nv	= (NV)SvIVX(sv);
	del_XIV(SvANY(sv));
	magic	= 0;
	stash	= 0;
	if (mt == SVt_NV)
	    mt = SVt_PVNV;
	else if (mt < SVt_PVIV)
	    mt = SVt_PVIV;
	break;
    case SVt_NV:
	pv	= 0;
	cur	= 0;
	len	= 0;
	nv	= SvNVX(sv);
	iv	= I_V(nv);
	magic	= 0;
	stash	= 0;
	del_XNV(SvANY(sv));
	SvANY(sv) = 0;
	if (mt < SVt_PVNV)
	    mt = SVt_PVNV;
	break;
    case SVt_RV:
	pv	= (char*)SvRV(sv);
	cur	= 0;
	len	= 0;
	iv	= (IV)PTR_CAST pv;
	nv	= (NV)(PTRV)pv;
	del_XRV(SvANY(sv));
	magic	= 0;
	stash	= 0;
	break;
    case SVt_PV:
	pv	= SvPVX(sv);
	cur	= SvCUR(sv);
	len	= SvLEN(sv);
	iv	= 0;
	nv	= 0.0;
	magic	= 0;
	stash	= 0;
	del_XPV(SvANY(sv));
	if (mt <= SVt_IV)
	    mt = SVt_PVIV;
	else if (mt == SVt_NV)
	    mt = SVt_PVNV;
	break;
    case SVt_PVIV:
	pv	= SvPVX(sv);
	cur	= SvCUR(sv);
	len	= SvLEN(sv);
	iv	= SvIVX(sv);
	nv	= 0.0;
	magic	= 0;
	stash	= 0;
	del_XPVIV(SvANY(sv));
	break;
    case SVt_PVNV:
	pv	= SvPVX(sv);
	cur	= SvCUR(sv);
	len	= SvLEN(sv);
	iv	= SvIVX(sv);
	nv	= SvNVX(sv);
	magic	= 0;
	stash	= 0;
	del_XPVNV(SvANY(sv));
	break;
    case SVt_PVMG:
	pv	= SvPVX(sv);
	cur	= SvCUR(sv);
	len	= SvLEN(sv);
	iv	= SvIVX(sv);
	nv	= SvNVX(sv);
	magic	= SvMAGIC(sv);
	stash	= SvSTASH(sv);
	del_XPVMG(SvANY(sv));
	break;
    default:
	Perl_croak(aTHX_ "Can't upgrade that kind of scalar");
    }

    switch (mt) {
    case SVt_NULL:
	Perl_croak(aTHX_ "Can't upgrade to undef");
    case SVt_IV:
	SvANY(sv) = new_XIV();
	SvIVX(sv)	= iv;
	break;
    case SVt_NV:
	SvANY(sv) = new_XNV();
	SvNVX(sv)	= nv;
	break;
    case SVt_RV:
	SvANY(sv) = new_XRV();
	SvRV(sv) = (SV*)pv;
	break;
    case SVt_PV:
	SvANY(sv) = new_XPV();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	break;
    case SVt_PVIV:
	SvANY(sv) = new_XPVIV();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	if (SvNIOK(sv))
	    (void)SvIOK_on(sv);
	SvNOK_off(sv);
	break;
    case SVt_PVNV:
	SvANY(sv) = new_XPVNV();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	break;
    case SVt_PVMG:
	SvANY(sv) = new_XPVMG();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	break;
    case SVt_PVLV:
	SvANY(sv) = new_XPVLV();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	LvTARGOFF(sv)	= 0;
	LvTARGLEN(sv)	= 0;
	LvTARG(sv)	= 0;
	LvTYPE(sv)	= 0;
	break;
    case SVt_PVAV:
	SvANY(sv) = new_XPVAV();
	if (pv)
	    Safefree(pv);
	SvPVX(sv)	= 0;
	AvMAX(sv)	= -1;
	AvFILLp(sv)	= -1;
	SvIVX(sv)	= 0;
	SvNVX(sv)	= 0.0;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	AvALLOC(sv)	= 0;
	AvARYLEN(sv)	= 0;
	AvFLAGS(sv)	= 0;
	break;
    case SVt_PVHV:
	SvANY(sv) = new_XPVHV();
	if (pv)
	    Safefree(pv);
	SvPVX(sv)	= 0;
	HvFILL(sv)	= 0;
	HvMAX(sv)	= 0;
	HvKEYS(sv)	= 0;
	SvNVX(sv)	= 0.0;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	HvRITER(sv)	= 0;
	HvEITER(sv)	= 0;
	HvPMROOT(sv)	= 0;
	HvNAME(sv)	= 0;
	break;
    case SVt_PVCV:
	SvANY(sv) = new_XPVCV();
	Zero(SvANY(sv), 1, XPVCV);
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	break;
    case SVt_PVGV:
	SvANY(sv) = new_XPVGV();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	GvGP(sv)	= 0;
	GvNAME(sv)	= 0;
	GvNAMELEN(sv)	= 0;
	GvSTASH(sv)	= 0;
	GvFLAGS(sv)	= 0;
	break;
    case SVt_PVBM:
	SvANY(sv) = new_XPVBM();
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	BmRARE(sv)	= 0;
	BmUSEFUL(sv)	= 0;
	BmPREVIOUS(sv)	= 0;
	break;
    case SVt_PVFM:
	SvANY(sv) = new_XPVFM();
	Zero(SvANY(sv), 1, XPVFM);
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	break;
    case SVt_PVIO:
	SvANY(sv) = new_XPVIO();
	Zero(SvANY(sv), 1, XPVIO);
	SvPVX(sv)	= pv;
	SvCUR(sv)	= cur;
	SvLEN(sv)	= len;
	SvIVX(sv)	= iv;
	SvNVX(sv)	= nv;
	SvMAGIC(sv)	= magic;
	SvSTASH(sv)	= stash;
	IoPAGE_LEN(sv)	= 60;
	break;
    }
    SvFLAGS(sv) &= ~SVTYPEMASK;
    SvFLAGS(sv) |= mt;
    return TRUE;
}

int
Perl_sv_backoff(pTHX_ register SV *sv)
{
    assert(SvOOK(sv));
    if (SvIVX(sv)) {
	char *s = SvPVX(sv);
	SvLEN(sv) += SvIVX(sv);
	SvPVX(sv) -= SvIVX(sv);
	SvIV_set(sv, 0);
	Move(s, SvPVX(sv), SvCUR(sv)+1, char);
    }
    SvFLAGS(sv) &= ~SVf_OOK;
    return 0;
}

char *
Perl_sv_grow(pTHX_ register SV *sv, register STRLEN newlen)
{
    register char *s;

#ifdef HAS_64K_LIMIT
    if (newlen >= 0x10000) {
	PerlIO_printf(Perl_debug_log, "Allocation too large: %lx\n", newlen);
	my_exit(1);
    }
#endif /* HAS_64K_LIMIT */
    if (SvROK(sv))
	sv_unref(sv);
    if (SvTYPE(sv) < SVt_PV) {
	sv_upgrade(sv, SVt_PV);
	s = SvPVX(sv);
    }
    else if (SvOOK(sv)) {	/* pv is offset? */
	sv_backoff(sv);
	s = SvPVX(sv);
	if (newlen > SvLEN(sv))
	    newlen += 10 * (newlen - SvCUR(sv)); /* avoid copy each time */
#ifdef HAS_64K_LIMIT
	if (newlen >= 0x10000)
	    newlen = 0xFFFF;
#endif
    }
    else
	s = SvPVX(sv);
    if (newlen > SvLEN(sv)) {		/* need more room? */
	if (SvLEN(sv) && s) {
#if defined(MYMALLOC) && !defined(PURIFY) && !defined(LEAKTEST)
	    STRLEN l = malloced_size((void*)SvPVX(sv));
	    if (newlen <= l) {
		SvLEN_set(sv, l);
		return s;
	    } else
#endif
	    Renew(s,newlen,char);
	}
        else
	    New(703,s,newlen,char);
	SvPV_set(sv, s);
        SvLEN_set(sv, newlen);
    }
    return s;
}

void
Perl_sv_setiv(pTHX_ register SV *sv, IV i)
{
    SV_CHECK_THINKFIRST(sv);
    switch (SvTYPE(sv)) {
    case SVt_NULL:
	sv_upgrade(sv, SVt_IV);
	break;
    case SVt_NV:
	sv_upgrade(sv, SVt_PVNV);
	break;
    case SVt_RV:
    case SVt_PV:
	sv_upgrade(sv, SVt_PVIV);
	break;

    case SVt_PVGV:
    case SVt_PVAV:
    case SVt_PVHV:
    case SVt_PVCV:
    case SVt_PVFM:
    case SVt_PVIO:
	{
	    dTHR;
	    Perl_croak(aTHX_ "Can't coerce %s to integer in %s", sv_reftype(sv,0),
		  PL_op_desc[PL_op->op_type]);
	}
    }
    (void)SvIOK_only(sv);			/* validate number */
    SvIVX(sv) = i;
    SvTAINT(sv);
}

void
Perl_sv_setiv_mg(pTHX_ register SV *sv, IV i)
{
    sv_setiv(sv,i);
    SvSETMAGIC(sv);
}

void
Perl_sv_setuv(pTHX_ register SV *sv, UV u)
{
    sv_setiv(sv, 0);
    SvIsUV_on(sv);
    SvUVX(sv) = u;
}

void
Perl_sv_setuv_mg(pTHX_ register SV *sv, UV u)
{
    sv_setuv(sv,u);
    SvSETMAGIC(sv);
}

void
Perl_sv_setnv(pTHX_ register SV *sv, NV num)
{
    SV_CHECK_THINKFIRST(sv);
    switch (SvTYPE(sv)) {
    case SVt_NULL:
    case SVt_IV:
	sv_upgrade(sv, SVt_NV);
	break;
    case SVt_RV:
    case SVt_PV:
    case SVt_PVIV:
	sv_upgrade(sv, SVt_PVNV);
	break;

    case SVt_PVGV:
    case SVt_PVAV:
    case SVt_PVHV:
    case SVt_PVCV:
    case SVt_PVFM:
    case SVt_PVIO:
	{
	    dTHR;
	    Perl_croak(aTHX_ "Can't coerce %s to number in %s", sv_reftype(sv,0),
		  PL_op_name[PL_op->op_type]);
	}
    }
    SvNVX(sv) = num;
    (void)SvNOK_only(sv);			/* validate number */
    SvTAINT(sv);
}

void
Perl_sv_setnv_mg(pTHX_ register SV *sv, NV num)
{
    sv_setnv(sv,num);
    SvSETMAGIC(sv);
}

STATIC void
S_not_a_number(pTHX_ SV *sv)
{
    dTHR;
    char tmpbuf[64];
    char *d = tmpbuf;
    char *s;
    char *limit = tmpbuf + sizeof(tmpbuf) - 8;
                  /* each *s can expand to 4 chars + "...\0",
                     i.e. need room for 8 chars */

    for (s = SvPVX(sv); *s && d < limit; s++) {
	int ch = *s & 0xFF;
	if (ch & 128 && !isPRINT_LC(ch)) {
	    *d++ = 'M';
	    *d++ = '-';
	    ch &= 127;
	}
	if (ch == '\n') {
	    *d++ = '\\';
	    *d++ = 'n';
	}
	else if (ch == '\r') {
	    *d++ = '\\';
	    *d++ = 'r';
	}
	else if (ch == '\f') {
	    *d++ = '\\';
	    *d++ = 'f';
	}
	else if (ch == '\\') {
	    *d++ = '\\';
	    *d++ = '\\';
	}
	else if (isPRINT_LC(ch))
	    *d++ = ch;
	else {
	    *d++ = '^';
	    *d++ = toCTRL(ch);
	}
    }
    if (*s) {
	*d++ = '.';
	*d++ = '.';
	*d++ = '.';
    }
    *d = '\0';

    if (PL_op)
	Perl_warner(aTHX_ WARN_NUMERIC, "Argument \"%s\" isn't numeric in %s", tmpbuf,
		PL_op_name[PL_op->op_type]);
    else
	Perl_warner(aTHX_ WARN_NUMERIC, "Argument \"%s\" isn't numeric", tmpbuf);
}

/* the number can be converted to integer with atol() or atoll() */
#define IS_NUMBER_TO_INT_BY_ATOL 0x01
#define IS_NUMBER_TO_INT_BY_ATOF 0x02 /* atol() may be != atof() */
#define IS_NUMBER_NOT_IV	 0x04 /* (IV)atof() may be != atof() */
#define IS_NUMBER_NEG		 0x08 /* not good to cache UV */

/* Actually, ISO C leaves conversion of UV to IV undefined, but
   until proven guilty, assume that things are not that bad... */

IV
Perl_sv_2iv(pTHX_ register SV *sv)
{
    if (!sv)
	return 0;
    if (SvGMAGICAL(sv)) {
	mg_get(sv);
	if (SvIOKp(sv))
	    return SvIVX(sv);
	if (SvNOKp(sv)) {
	    return I_V(SvNVX(sv));
	}
	if (SvPOKp(sv) && SvLEN(sv))
	    return asIV(sv);
	if (!SvROK(sv)) {
	    if (!(SvFLAGS(sv) & SVs_PADTMP)) {
		dTHR;
		if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing)
		    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    }
	    return 0;
	}
    }
    if (SvTHINKFIRST(sv)) {
	if (SvROK(sv)) {
	  SV* tmpstr;
	  if (SvAMAGIC(sv) && (tmpstr=AMG_CALLun(sv, numer)))
	      return SvIV(tmpstr);
	  return (IV)PTR_CAST SvRV(sv);
	}
	if (SvREADONLY(sv) && !SvOK(sv)) {
	    dTHR;
	    if (ckWARN(WARN_UNINITIALIZED))
		Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    return 0;
	}
    }
    if (SvIOKp(sv)) {
	if (SvIsUV(sv)) {
	    return (IV)(SvUVX(sv));
	}
	else {
	    return SvIVX(sv);
	}
    }
    if (SvNOKp(sv)) {
	/* We can cache the IV/UV value even if it not good enough
	 * to reconstruct NV, since the conversion to PV will prefer
	 * NV over IV/UV.
	 */

	if (SvTYPE(sv) == SVt_NV)
	    sv_upgrade(sv, SVt_PVNV);

	(void)SvIOK_on(sv);
	if (SvNVX(sv) < (NV)IV_MAX + 0.5)
	    SvIVX(sv) = I_V(SvNVX(sv));
	else {
	    SvUVX(sv) = U_V(SvNVX(sv));
	    SvIsUV_on(sv);
	  ret_iv_max:
#ifdef IV_IS_QUAD
	    DEBUG_c(PerlIO_printf(Perl_debug_log, 
				  "0x%" PERL_PRIx64 " 2iv(%" PERL_PRIu64 " => %" PERL_PRId64 ") (as unsigned)\n",
				  (UV)PTR_CAST sv,
				  (UV)SvUVX(sv), (IV)SvUVX(sv)));
#else
	    DEBUG_c(PerlIO_printf(Perl_debug_log, 
				  "0x%lx 2iv(%lu => %ld) (as unsigned)\n",
				  (unsigned long)sv,
				  (unsigned long)SvUVX(sv), (long)(IV)SvUVX(sv)));
#endif
	    return (IV)SvUVX(sv);
	}
    }
    else if (SvPOKp(sv) && SvLEN(sv)) {
	I32 numtype = looks_like_number(sv);

	/* We want to avoid a possible problem when we cache an IV which
	   may be later translated to an NV, and the resulting NV is not
	   the translation of the initial data.
	  
	   This means that if we cache such an IV, we need to cache the
	   NV as well.  Moreover, we trade speed for space, and do not
	   cache the NV if not needed.
	 */
	if (numtype & IS_NUMBER_NOT_IV) {
	    /* May be not an integer.  Need to cache NV if we cache IV
	     * - otherwise future conversion to NV will be wrong.  */
	    NV d;

	    d = Atof(SvPVX(sv));

	    if (SvTYPE(sv) < SVt_PVNV)
		sv_upgrade(sv, SVt_PVNV);
	    SvNVX(sv) = d;
	    (void)SvNOK_on(sv);
	    (void)SvIOK_on(sv);
#if defined(USE_LONG_DOUBLE)
	    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2nv(%" PERL_PRIgldbl ")\n",
				  (unsigned long)sv, SvNVX(sv)));
#else
	    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2nv(%g)\n",
				  (unsigned long)sv, SvNVX(sv)));
#endif
	    if (SvNVX(sv) < (NV)IV_MAX + 0.5)
		SvIVX(sv) = I_V(SvNVX(sv));
	    else {
		SvUVX(sv) = U_V(SvNVX(sv));
		SvIsUV_on(sv);
		goto ret_iv_max;
	    }
	}
	else if (numtype) {
	    /* The NV may be reconstructed from IV - safe to cache IV,
	       which may be calculated by atol(). */
	    if (SvTYPE(sv) == SVt_PV)
		sv_upgrade(sv, SVt_PVIV);
	    (void)SvIOK_on(sv);
	    SvIVX(sv) = Atol(SvPVX(sv));
	}
	else {				/* Not a number.  Cache 0. */
	    dTHR;

	    if (SvTYPE(sv) < SVt_PVIV)
		sv_upgrade(sv, SVt_PVIV);
	    SvIVX(sv) = 0;
	    (void)SvIOK_on(sv);
	    if (ckWARN(WARN_NUMERIC))
		not_a_number(sv);
	}
    }
    else  {
	dTHR;
	if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing && !(SvFLAGS(sv) & SVs_PADTMP))
	    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	if (SvTYPE(sv) < SVt_IV)
	    /* Typically the caller expects that sv_any is not NULL now.  */
	    sv_upgrade(sv, SVt_IV);
	return 0;
    }
    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2iv(%ld)\n",
	(unsigned long)sv,(long)SvIVX(sv)));
    return SvIsUV(sv) ? (IV)SvUVX(sv) : SvIVX(sv);
}

UV
Perl_sv_2uv(pTHX_ register SV *sv)
{
    if (!sv)
	return 0;
    if (SvGMAGICAL(sv)) {
	mg_get(sv);
	if (SvIOKp(sv))
	    return SvUVX(sv);
	if (SvNOKp(sv))
	    return U_V(SvNVX(sv));
	if (SvPOKp(sv) && SvLEN(sv))
	    return asUV(sv);
	if (!SvROK(sv)) {
	    if (!(SvFLAGS(sv) & SVs_PADTMP)) {
		dTHR;
		if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing)
		    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    }
	    return 0;
	}
    }
    if (SvTHINKFIRST(sv)) {
	if (SvROK(sv)) {
	  SV* tmpstr;
	  if (SvAMAGIC(sv) && (tmpstr=AMG_CALLun(sv, numer)))
	      return SvUV(tmpstr);
	  return (UV)PTR_CAST SvRV(sv);
	}
	if (SvREADONLY(sv) && !SvOK(sv)) {
	    dTHR;
	    if (ckWARN(WARN_UNINITIALIZED))
		Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    return 0;
	}
    }
    if (SvIOKp(sv)) {
	if (SvIsUV(sv)) {
	    return SvUVX(sv);
	}
	else {
	    return (UV)SvIVX(sv);
	}
    }
    if (SvNOKp(sv)) {
	/* We can cache the IV/UV value even if it not good enough
	 * to reconstruct NV, since the conversion to PV will prefer
	 * NV over IV/UV.
	 */
	if (SvTYPE(sv) == SVt_NV)
	    sv_upgrade(sv, SVt_PVNV);
	(void)SvIOK_on(sv);
	if (SvNVX(sv) >= -0.5) {
	    SvIsUV_on(sv);
	    SvUVX(sv) = U_V(SvNVX(sv));
	}
	else {
	    SvIVX(sv) = I_V(SvNVX(sv));
	  ret_zero:
#ifdef IV_IS_QUAD
	    DEBUG_c(PerlIO_printf(Perl_debug_log, 
				  "0x%" PERL_PRIx64 " 2uv(%" PERL_PRId64 " => %" PERL_PRIu64 ") (as signed)\n",
				  (unsigned long)sv,(long)SvIVX(sv),
				  (long)(UV)SvIVX(sv)));
#else
	    DEBUG_c(PerlIO_printf(Perl_debug_log, 
				  "0x%lx 2uv(%ld => %lu) (as signed)\n",
				  (unsigned long)sv,(long)SvIVX(sv),
				  (long)(UV)SvIVX(sv)));
#endif
	    return (UV)SvIVX(sv);
	}
    }
    else if (SvPOKp(sv) && SvLEN(sv)) {
	I32 numtype = looks_like_number(sv);

	/* We want to avoid a possible problem when we cache a UV which
	   may be later translated to an NV, and the resulting NV is not
	   the translation of the initial data.
	  
	   This means that if we cache such a UV, we need to cache the
	   NV as well.  Moreover, we trade speed for space, and do not
	   cache the NV if not needed.
	 */
	if (numtype & IS_NUMBER_NOT_IV) {
	    /* May be not an integer.  Need to cache NV if we cache IV
	     * - otherwise future conversion to NV will be wrong.  */
	    NV d;

	    d = Atof(SvPVX(sv));

	    if (SvTYPE(sv) < SVt_PVNV)
		sv_upgrade(sv, SVt_PVNV);
	    SvNVX(sv) = d;
	    (void)SvNOK_on(sv);
	    (void)SvIOK_on(sv);
#if defined(USE_LONG_DOUBLE)
	    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2nv(%" PERL_PRIgldbl ")\n",
				  (unsigned long)sv, SvNVX(sv)));
#else
	    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2nv(%g)\n",
				  (unsigned long)sv, SvNVX(sv)));
#endif
	    if (SvNVX(sv) < -0.5) {
		SvIVX(sv) = I_V(SvNVX(sv));
		goto ret_zero;
	    } else {
		SvUVX(sv) = U_V(SvNVX(sv));
		SvIsUV_on(sv);
	    }
	}
	else if (numtype & IS_NUMBER_NEG) {
	    /* The NV may be reconstructed from IV - safe to cache IV,
	       which may be calculated by atol(). */
	    if (SvTYPE(sv) == SVt_PV)
		sv_upgrade(sv, SVt_PVIV);
	    (void)SvIOK_on(sv);
	    SvIVX(sv) = (IV)Atol(SvPVX(sv));
	}
	else if (numtype) {		/* Non-negative */
	    /* The NV may be reconstructed from UV - safe to cache UV,
	       which may be calculated by strtoul()/atol. */
	    if (SvTYPE(sv) == SVt_PV)
		sv_upgrade(sv, SVt_PVIV);
	    (void)SvIOK_on(sv);
	    (void)SvIsUV_on(sv);
#ifdef HAS_STRTOUL
	    SvUVX(sv) = Strtoul(SvPVX(sv), Null(char**), 10);
#else			/* no atou(), but we know the number fits into IV... */
	    		/* The only problem may be if it is negative... */
	    SvUVX(sv) = (UV)Atol(SvPVX(sv));
#endif
	}
	else {				/* Not a number.  Cache 0. */
	    dTHR;

	    if (SvTYPE(sv) < SVt_PVIV)
		sv_upgrade(sv, SVt_PVIV);
	    SvUVX(sv) = 0;		/* We assume that 0s have the
					   same bitmap in IV and UV. */
	    (void)SvIOK_on(sv);
	    (void)SvIsUV_on(sv);
	    if (ckWARN(WARN_NUMERIC))
		not_a_number(sv);
	}
    }
    else  {
	if (!(SvFLAGS(sv) & SVs_PADTMP)) {
	    dTHR;
	    if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing)
		Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	}
	if (SvTYPE(sv) < SVt_IV)
	    /* Typically the caller expects that sv_any is not NULL now.  */
	    sv_upgrade(sv, SVt_IV);
	return 0;
    }

    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2uv(%lu)\n",
	(unsigned long)sv,SvUVX(sv)));
    return SvIsUV(sv) ? SvUVX(sv) : (UV)SvIVX(sv);
}

NV
Perl_sv_2nv(pTHX_ register SV *sv)
{
    if (!sv)
	return 0.0;
    if (SvGMAGICAL(sv)) {
	mg_get(sv);
	if (SvNOKp(sv))
	    return SvNVX(sv);
	if (SvPOKp(sv) && SvLEN(sv)) {
	    dTHR;
	    if (ckWARN(WARN_NUMERIC) && !SvIOKp(sv) && !looks_like_number(sv))
		not_a_number(sv);
	    return Atof(SvPVX(sv));
	}
	if (SvIOKp(sv)) {
	    if (SvIsUV(sv)) 
		return (NV)SvUVX(sv);
	    else
		return (NV)SvIVX(sv);
	}	
        if (!SvROK(sv)) {
	    if (!(SvFLAGS(sv) & SVs_PADTMP)) {
		dTHR;
		if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing)
		    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    }
            return 0;
        }
    }
    if (SvTHINKFIRST(sv)) {
	if (SvROK(sv)) {
	  SV* tmpstr;
	  if (SvAMAGIC(sv) && (tmpstr=AMG_CALLun(sv,numer)))
	      return SvNV(tmpstr);
	  return (NV)(PTRV)SvRV(sv);
	}
	if (SvREADONLY(sv) && !SvOK(sv)) {
	    dTHR;
	    if (ckWARN(WARN_UNINITIALIZED))
		Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    return 0.0;
	}
    }
    if (SvTYPE(sv) < SVt_NV) {
	if (SvTYPE(sv) == SVt_IV)
	    sv_upgrade(sv, SVt_PVNV);
	else
	    sv_upgrade(sv, SVt_NV);
#if defined(USE_LONG_DOUBLE)
	DEBUG_c({
	    RESTORE_NUMERIC_STANDARD();
	    PerlIO_printf(Perl_debug_log, "0x%lx num(%" PERL_PRIgldbl ")\n",
			  (unsigned long)sv, SvNVX(sv));
	    RESTORE_NUMERIC_LOCAL();
	});
#else
	DEBUG_c({
	    RESTORE_NUMERIC_STANDARD();
	    PerlIO_printf(Perl_debug_log, "0x%lx num(%g)\n",
			  (unsigned long)sv, SvNVX(sv));
	    RESTORE_NUMERIC_LOCAL();
	});
#endif
    }
    else if (SvTYPE(sv) < SVt_PVNV)
	sv_upgrade(sv, SVt_PVNV);
    if (SvIOKp(sv) &&
	    (!SvPOKp(sv) || !strchr(SvPVX(sv),'.') || !looks_like_number(sv)))
    {
	SvNVX(sv) = SvIsUV(sv) ? (NV)SvUVX(sv) : (NV)SvIVX(sv);
    }
    else if (SvPOKp(sv) && SvLEN(sv)) {
	dTHR;
	if (ckWARN(WARN_NUMERIC) && !SvIOKp(sv) && !looks_like_number(sv))
	    not_a_number(sv);
	SvNVX(sv) = Atof(SvPVX(sv));
    }
    else  {
	dTHR;
	if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing && !(SvFLAGS(sv) & SVs_PADTMP))
	    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	if (SvTYPE(sv) < SVt_NV)
	    /* Typically the caller expects that sv_any is not NULL now.  */
	    sv_upgrade(sv, SVt_NV);
	return 0.0;
    }
    SvNOK_on(sv);
#if defined(USE_LONG_DOUBLE)
    DEBUG_c({
	RESTORE_NUMERIC_STANDARD();
	PerlIO_printf(Perl_debug_log, "0x%lx 2nv(%" PERL_PRIgldbl ")\n",
		      (unsigned long)sv, SvNVX(sv));
	RESTORE_NUMERIC_LOCAL();
    });
#else
    DEBUG_c({
	RESTORE_NUMERIC_STANDARD();
	PerlIO_printf(Perl_debug_log, "0x%lx 1nv(%g)\n",
		      (unsigned long)sv, SvNVX(sv));
	RESTORE_NUMERIC_LOCAL();
    });
#endif
    return SvNVX(sv);
}

STATIC IV
S_asIV(pTHX_ SV *sv)
{
    I32 numtype = looks_like_number(sv);
    NV d;

    if (numtype & IS_NUMBER_TO_INT_BY_ATOL)
	return Atol(SvPVX(sv));
    if (!numtype) {
	dTHR;
	if (ckWARN(WARN_NUMERIC))
	    not_a_number(sv);
    }
    d = Atof(SvPVX(sv));
    return I_V(d);
}

STATIC UV
S_asUV(pTHX_ SV *sv)
{
    I32 numtype = looks_like_number(sv);

#ifdef HAS_STRTOUL
    if (numtype & IS_NUMBER_TO_INT_BY_ATOL)
	return Strtoul(SvPVX(sv), Null(char**), 10);
#endif
    if (!numtype) {
	dTHR;
	if (ckWARN(WARN_NUMERIC))
	    not_a_number(sv);
    }
    return U_V(Atof(SvPVX(sv)));
}

/*
 * Returns a combination of (advisory only - can get false negatives)
 * 	IS_NUMBER_TO_INT_BY_ATOL, IS_NUMBER_TO_INT_BY_ATOF, IS_NUMBER_NOT_IV,
 *	IS_NUMBER_NEG
 * 0 if does not look like number.
 *
 * In fact possible values are 0 and
 * IS_NUMBER_TO_INT_BY_ATOL				123
 * IS_NUMBER_TO_INT_BY_ATOL | IS_NUMBER_NOT_IV		123.1
 * IS_NUMBER_TO_INT_BY_ATOF | IS_NUMBER_NOT_IV		123e0
 * with a possible addition of IS_NUMBER_NEG.
 */

I32
Perl_looks_like_number(pTHX_ SV *sv)
{
    register char *s;
    register char *send;
    register char *sbegin;
    register char *nbegin;
    I32 numtype = 0;
    STRLEN len;

    if (SvPOK(sv)) {
	sbegin = SvPVX(sv); 
	len = SvCUR(sv);
    }
    else if (SvPOKp(sv))
	sbegin = SvPV(sv, len);
    else
	return 1;
    send = sbegin + len;

    s = sbegin;
    while (isSPACE(*s))
	s++;
    if (*s == '-') {
	s++;
	numtype = IS_NUMBER_NEG;
    }
    else if (*s == '+')
	s++;

    nbegin = s;
    /*
     * we return IS_NUMBER_TO_INT_BY_ATOL if the number can be converted
     * to _integer_ with atol() and IS_NUMBER_TO_INT_BY_ATOF if you need
     * (int)atof().
     */

    /* next must be digit or the radix separator */
    if (isDIGIT(*s)) {
        do {
	    s++;
        } while (isDIGIT(*s));

	if (s - nbegin >= TYPE_DIGITS(IV))	/* Cannot cache ato[ul]() */
	    numtype |= IS_NUMBER_TO_INT_BY_ATOF | IS_NUMBER_NOT_IV;
	else
	    numtype |= IS_NUMBER_TO_INT_BY_ATOL;

        if (*s == '.'
#ifdef USE_LOCALE_NUMERIC 
	    || IS_NUMERIC_RADIX(*s)
#endif
	    ) {
	    s++;
	    numtype |= IS_NUMBER_NOT_IV;
            while (isDIGIT(*s))  /* optional digits after the radix */
                s++;
        }
    }
    else if (*s == '.'
#ifdef USE_LOCALE_NUMERIC 
	    || IS_NUMERIC_RADIX(*s)
#endif
	    ) {
        s++;
	numtype |= IS_NUMBER_TO_INT_BY_ATOL | IS_NUMBER_NOT_IV;
        /* no digits before the radix means we need digits after it */
        if (isDIGIT(*s)) {
	    do {
	        s++;
            } while (isDIGIT(*s));
        }
        else
	    return 0;
    }
    else
        return 0;

    /* we can have an optional exponent part */
    if (*s == 'e' || *s == 'E') {
	numtype &= ~IS_NUMBER_NEG;
	numtype |= IS_NUMBER_TO_INT_BY_ATOF | IS_NUMBER_NOT_IV;
	s++;
	if (*s == '+' || *s == '-')
	    s++;
        if (isDIGIT(*s)) {
            do {
                s++;
            } while (isDIGIT(*s));
        }
        else
            return 0;
    }
    while (isSPACE(*s))
	s++;
    if (s >= send)
	return numtype;
    if (len == 10 && memEQ(sbegin, "0 but true", 10))
	return IS_NUMBER_TO_INT_BY_ATOL;
    return 0;
}

char *
Perl_sv_2pv_nolen(pTHX_ register SV *sv)
{
    STRLEN n_a;
    return sv_2pv(sv, &n_a);
}

/* We assume that buf is at least TYPE_CHARS(UV) long. */
static char *
uiv_2buf(char *buf, IV iv, UV uv, int is_uv, char **peob)
{
    STRLEN len;
    char *ptr = buf + TYPE_CHARS(UV);
    char *ebuf = ptr;
    int sign;
    char *p;

    if (is_uv)
	sign = 0;
    else if (iv >= 0) {
	uv = iv;
	sign = 0;
    } else {
	uv = -iv;
	sign = 1;
    }
    do {
	*--ptr = '0' + (uv % 10);
    } while (uv /= 10);
    if (sign)
	*--ptr = '-';
    *peob = ebuf;
    return ptr;
}

char *
Perl_sv_2pv(pTHX_ register SV *sv, STRLEN *lp)
{
    register char *s;
    int olderrno;
    SV *tsv;
    char tbuf[64];	/* Must fit sprintf/Gconvert of longest IV/NV */
    char *tmpbuf = tbuf;

    if (!sv) {
	*lp = 0;
	return "";
    }
    if (SvGMAGICAL(sv)) {
	mg_get(sv);
	if (SvPOKp(sv)) {
	    *lp = SvCUR(sv);
	    return SvPVX(sv);
	}
	if (SvIOKp(sv)) {
#ifdef IV_IS_QUAD
	    if (SvIsUV(sv)) 
		(void)sprintf(tmpbuf,"%" PERL_PRIu64,(UV)SvUVX(sv));
	    else
		(void)sprintf(tmpbuf,"%" PERL_PRId64,(IV)SvIVX(sv));
#else
	    if (SvIsUV(sv)) 
		(void)sprintf(tmpbuf,"%lu",(unsigned long)SvUVX(sv));
	    else
		(void)sprintf(tmpbuf,"%ld",(long)SvIVX(sv));
#endif
	    tsv = Nullsv;
	    goto tokensave;
	}
	if (SvNOKp(sv)) {
	    Gconvert(SvNVX(sv), NV_DIG, 0, tmpbuf);
	    tsv = Nullsv;
	    goto tokensave;
	}
        if (!SvROK(sv)) {
	    if (!(SvFLAGS(sv) & SVs_PADTMP)) {
		dTHR;
		if (ckWARN(WARN_UNINITIALIZED) && !PL_localizing)
		    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    }
            *lp = 0;
            return "";
        }
    }
    if (SvTHINKFIRST(sv)) {
	if (SvROK(sv)) {
	    SV* tmpstr;
	    if (SvAMAGIC(sv) && (tmpstr=AMG_CALLun(sv,string)))
		return SvPV(tmpstr,*lp);
	    sv = (SV*)SvRV(sv);
	    if (!sv)
		s = "NULLREF";
	    else {
		MAGIC *mg;
		
		switch (SvTYPE(sv)) {
		case SVt_PVMG:
		    if ( ((SvFLAGS(sv) &
			   (SVs_OBJECT|SVf_OK|SVs_GMG|SVs_SMG|SVs_RMG)) 
			  == (SVs_OBJECT|SVs_RMG))
			 && strEQ(s=HvNAME(SvSTASH(sv)), "Regexp")
			 && (mg = mg_find(sv, 'r'))) {
			dTHR;
			regexp *re = (regexp *)mg->mg_obj;

			if (!mg->mg_ptr) {
			    char *fptr = "msix";
			    char reflags[6];
			    char ch;
			    int left = 0;
			    int right = 4;
 			    U16 reganch = (re->reganch & PMf_COMPILETIME) >> 12;

 			    while(ch = *fptr++) {
 				if(reganch & 1) {
 				    reflags[left++] = ch;
 				}
 				else {
 				    reflags[right--] = ch;
 				}
 				reganch >>= 1;
 			    }
 			    if(left != 4) {
 				reflags[left] = '-';
 				left = 5;
 			    }

			    mg->mg_len = re->prelen + 4 + left;
			    New(616, mg->mg_ptr, mg->mg_len + 1 + left, char);
			    Copy("(?", mg->mg_ptr, 2, char);
			    Copy(reflags, mg->mg_ptr+2, left, char);
			    Copy(":", mg->mg_ptr+left+2, 1, char);
			    Copy(re->precomp, mg->mg_ptr+3+left, re->prelen, char);
			    mg->mg_ptr[mg->mg_len - 1] = ')';
			    mg->mg_ptr[mg->mg_len] = 0;
			}
			PL_reginterp_cnt += re->program[0].next_off;
			*lp = mg->mg_len;
			return mg->mg_ptr;
		    }
					/* Fall through */
		case SVt_NULL:
		case SVt_IV:
		case SVt_NV:
		case SVt_RV:
		case SVt_PV:
		case SVt_PVIV:
		case SVt_PVNV:
		case SVt_PVBM:	s = "SCALAR";			break;
		case SVt_PVLV:	s = "LVALUE";			break;
		case SVt_PVAV:	s = "ARRAY";			break;
		case SVt_PVHV:	s = "HASH";			break;
		case SVt_PVCV:	s = "CODE";			break;
		case SVt_PVGV:	s = "GLOB";			break;
		case SVt_PVFM:	s = "FORMAT";			break;
		case SVt_PVIO:	s = "IO";			break;
		default:	s = "UNKNOWN";			break;
		}
		tsv = NEWSV(0,0);
		if (SvOBJECT(sv))
		    Perl_sv_setpvf(aTHX_ tsv, "%s=%s", HvNAME(SvSTASH(sv)), s);
		else
		    sv_setpv(tsv, s);
#ifdef IV_IS_QUAD
		Perl_sv_catpvf(aTHX_ tsv, "(0x%" PERL_PRIx64")", (UV)PTR_CAST sv);
#else
		Perl_sv_catpvf(aTHX_ tsv, "(0x%lx)", (unsigned long)sv);
#endif
		goto tokensaveref;
	    }
	    *lp = strlen(s);
	    return s;
	}
	if (SvREADONLY(sv) && !SvOK(sv)) {
	    dTHR;
	    if (ckWARN(WARN_UNINITIALIZED))
		Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	    *lp = 0;
	    return "";
	}
    }
    if (SvNOKp(sv)) {			/* See note in sv_2uv() */
	/* XXXX 64-bit?  IV may have better precision... */
	/* I tried changing this for to be 64-bit-aware and
	 * the t/op/numconvert.t became very, very, angry.
	 * --jhi Sep 1999 */
	if (SvTYPE(sv) < SVt_PVNV)
	    sv_upgrade(sv, SVt_PVNV);
	SvGROW(sv, 28);
	s = SvPVX(sv);
	olderrno = errno;	/* some Xenix systems wipe out errno here */
#ifdef apollo
	if (SvNVX(sv) == 0.0)
	    (void)strcpy(s,"0");
	else
#endif /*apollo*/
	{
	    Gconvert(SvNVX(sv), NV_DIG, 0, s);
	}
	errno = olderrno;
#ifdef FIXNEGATIVEZERO
        if (*s == '-' && s[1] == '0' && !s[2])
	    strcpy(s,"0");
#endif
	while (*s) s++;
#ifdef hcx
	if (s[-1] == '.')
	    *--s = '\0';
#endif
    }
    else if (SvIOKp(sv)) {
	U32 isIOK = SvIOK(sv);
	U32 isUIOK = SvIsUV(sv);
	char buf[TYPE_CHARS(UV)];
	char *ebuf, *ptr;

	if (SvTYPE(sv) < SVt_PVIV)
	    sv_upgrade(sv, SVt_PVIV);
	if (isUIOK)
	    ptr = uiv_2buf(buf, 0, SvUVX(sv), 1, &ebuf);
	else
	    ptr = uiv_2buf(buf, SvIVX(sv), 0, 0, &ebuf);
	SvGROW(sv, ebuf - ptr + 1);	/* inlined from sv_setpvn */
	Move(ptr,SvPVX(sv),ebuf - ptr,char);
	SvCUR_set(sv, ebuf - ptr);
	s = SvEND(sv);
	*s = '\0';
	if (isIOK)
	    SvIOK_on(sv);
	else
	    SvIOKp_on(sv);
	if (isUIOK)
	    SvIsUV_on(sv);
	SvPOK_on(sv);
    }
    else {
	dTHR;
	if (ckWARN(WARN_UNINITIALIZED)
	    && !PL_localizing && !(SvFLAGS(sv) & SVs_PADTMP))
	{
	    Perl_warner(aTHX_ WARN_UNINITIALIZED, PL_warn_uninit);
	}
	*lp = 0;
	if (SvTYPE(sv) < SVt_PV)
	    /* Typically the caller expects that sv_any is not NULL now.  */
	    sv_upgrade(sv, SVt_PV);
	return "";
    }
    *lp = s - SvPVX(sv);
    SvCUR_set(sv, *lp);
    SvPOK_on(sv);
    DEBUG_c(PerlIO_printf(Perl_debug_log, "0x%lx 2pv(%s)\n",
			  (unsigned long)sv,SvPVX(sv)));
    return SvPVX(sv);

  tokensave:
    if (SvROK(sv)) {	/* XXX Skip this when sv_pvn_force calls */
	/* Sneaky stuff here */

      tokensaveref:
	if (!tsv)
	    tsv = newSVpv(tmpbuf, 0);
	sv_2mortal(tsv);
	*lp = SvCUR(tsv);
	return SvPVX(tsv);
    }
    else {
	STRLEN len;
	char *t;

	if (tsv) {
	    sv_2mortal(tsv);
	    t = SvPVX(tsv);
	    len = SvCUR(tsv);
	}
	else {
	    t = tmpbuf;
	    len = strlen(tmpbuf);
	}
#ifdef FIXNEGATIVEZERO
	if (len == 2 && t[0] == '-' && t[1] == '0') {
	    t = "0";
	    len = 1;
	}
#endif
	(void)SvUPGRADE(sv, SVt_PV);
	*lp = len;
	s = SvGROW(sv, len + 1);
	SvCUR_set(sv, len);
	(void)strcpy(s, t);
	SvPOKp_on(sv);
	return s;
    }
}

/* This function is only called on magical items */
bool
Perl_sv_2bool(pTHX_ register SV *sv)
{
    if (SvGMAGICAL(sv))
	mg_get(sv);

    if (!SvOK(sv))
	return 0;
    if (SvROK(sv)) {
	dTHR;
	SV* tmpsv;
	if (SvAMAGIC(sv) && (tmpsv = AMG_CALLun(sv,bool_)))
	    return SvTRUE(tmpsv);
      return SvRV(sv) != 0;
    }
    if (SvPOKp(sv)) {
	register XPV* Xpvtmp;
	if ((Xpvtmp = (XPV*)SvANY(sv)) &&
		(*Xpvtmp->xpv_pv > '0' ||
		Xpvtmp->xpv_cur > 1 ||
		(Xpvtmp->xpv_cur && *Xpvtmp->xpv_pv != '0')))
	    return 1;
	else
	    return 0;
    }
    else {
	if (SvIOKp(sv))
	    return SvIVX(sv) != 0;
	else {
	    if (SvNOKp(sv))
		return SvNVX(sv) != 0.0;
	    else
		return FALSE;
	}
    }
}

/* Note: sv_setsv() should not be called with a source string that needs
 * to be reused, since it may destroy the source string if it is marked
 * as temporary.
 */

void
Perl_sv_setsv(pTHX_ SV *dstr, register SV *sstr)
{
    dTHR;
    register U32 sflags;
    register int dtype;
    register int stype;

    if (sstr == dstr)
	return;
    SV_CHECK_THINKFIRST(dstr);
    if (!sstr)
	sstr = &PL_sv_undef;
    stype = SvTYPE(sstr);
    dtype = SvTYPE(dstr);

    SvAMAGIC_off(dstr);

    /* There's a lot of redundancy below but we're going for speed here */

    switch (stype) {
    case SVt_NULL:
      undef_sstr:
	if (dtype != SVt_PVGV) {
	    (void)SvOK_off(dstr);
	    return;
	}
	break;
    case SVt_IV:
	if (SvIOK(sstr)) {
	    switch (dtype) {
	    case SVt_NULL:
		sv_upgrade(dstr, SVt_IV);
		break;
	    case SVt_NV:
		sv_upgrade(dstr, SVt_PVNV);
		break;
	    case SVt_RV:
	    case SVt_PV:
		sv_upgrade(dstr, SVt_PVIV);
		break;
	    }
	    (void)SvIOK_only(dstr);
	    SvIVX(dstr) = SvIVX(sstr);
	    if (SvIsUV(sstr))
		SvIsUV_on(dstr);
	    SvTAINT(dstr);
	    return;
	}
	goto undef_sstr;

    case SVt_NV:
	if (SvNOK(sstr)) {
	    switch (dtype) {
	    case SVt_NULL:
	    case SVt_IV:
		sv_upgrade(dstr, SVt_NV);
		break;
	    case SVt_RV:
	    case SVt_PV:
	    case SVt_PVIV:
		sv_upgrade(dstr, SVt_PVNV);
		break;
	    }
	    SvNVX(dstr) = SvNVX(sstr);
	    (void)SvNOK_only(dstr);
	    SvTAINT(dstr);
	    return;
	}
	goto undef_sstr;

    case SVt_RV:
	if (dtype < SVt_RV)
	    sv_upgrade(dstr, SVt_RV);
	else if (dtype == SVt_PVGV &&
		 SvTYPE(SvRV(sstr)) == SVt_PVGV) {
	    sstr = SvRV(sstr);
	    if (sstr == dstr) {
		if (PL_curcop->cop_stash != GvSTASH(dstr))
		    GvIMPORTED_on(dstr);
		GvMULTI_on(dstr);
		return;
	    }
	    goto glob_assign;
	}
	break;
    case SVt_PV:
    case SVt_PVFM:
	if (dtype < SVt_PV)
	    sv_upgrade(dstr, SVt_PV);
	break;
    case SVt_PVIV:
	if (dtype < SVt_PVIV)
	    sv_upgrade(dstr, SVt_PVIV);
	break;
    case SVt_PVNV:
	if (dtype < SVt_PVNV)
	    sv_upgrade(dstr, SVt_PVNV);
	break;
    case SVt_PVAV:
    case SVt_PVHV:
    case SVt_PVCV:
    case SVt_PVIO:
	if (PL_op)
	    Perl_croak(aTHX_ "Bizarre copy of %s in %s", sv_reftype(sstr, 0),
		PL_op_name[PL_op->op_type]);
	else
	    Perl_croak(aTHX_ "Bizarre copy of %s", sv_reftype(sstr, 0));
	break;

    case SVt_PVGV:
	if (dtype <= SVt_PVGV) {
  glob_assign:
	    if (dtype != SVt_PVGV) {
		char *name = GvNAME(sstr);
		STRLEN len = GvNAMELEN(sstr);
		sv_upgrade(dstr, SVt_PVGV);
		sv_magic(dstr, dstr, '*', name, len);
		GvSTASH(dstr) = (HV*)SvREFCNT_inc(GvSTASH(sstr));
		GvNAME(dstr) = savepvn(name, len);
		GvNAMELEN(dstr) = len;
		SvFAKE_on(dstr);	/* can coerce to non-glob */
	    }
	    /* ahem, death to those who redefine active sort subs */
	    else if (PL_curstackinfo->si_type == PERLSI_SORT
		     && GvCV(dstr) && PL_sortcop == CvSTART(GvCV(dstr)))
		Perl_croak(aTHX_ "Can't redefine active sort subroutine %s",
		      GvNAME(dstr));
	    (void)SvOK_off(dstr);
	    GvINTRO_off(dstr);		/* one-shot flag */
	    gp_free((GV*)dstr);
	    GvGP(dstr) = gp_ref(GvGP(sstr));
	    SvTAINT(dstr);
	    if (PL_curcop->cop_stash != GvSTASH(dstr))
		GvIMPORTED_on(dstr);
	    GvMULTI_on(dstr);
	    return;
	}
	/* FALL THROUGH */

    default:
	if (SvGMAGICAL(sstr)) {
	    mg_get(sstr);
	    if (SvTYPE(sstr) != stype) {
		stype = SvTYPE(sstr);
		if (stype == SVt_PVGV && dtype <= SVt_PVGV)
		    goto glob_assign;
	    }
	}
	if (stype == SVt_PVLV)
	    (void)SvUPGRADE(dstr, SVt_PVNV);
	else
	    (void)SvUPGRADE(dstr, stype);
    }

    sflags = SvFLAGS(sstr);

    if (sflags & SVf_ROK) {
	if (dtype >= SVt_PV) {
	    if (dtype == SVt_PVGV) {
		SV *sref = SvREFCNT_inc(SvRV(sstr));
		SV *dref = 0;
		int intro = GvINTRO(dstr);

		if (intro) {
		    GP *gp;
		    GvGP(dstr)->gp_refcnt--;
		    GvINTRO_off(dstr);	/* one-shot flag */
		    Newz(602,gp, 1, GP);
		    GvGP(dstr) = gp_ref(gp);
		    GvSV(dstr) = NEWSV(72,0);
		    GvLINE(dstr) = PL_curcop->cop_line;
		    GvEGV(dstr) = (GV*)dstr;
		}
		GvMULTI_on(dstr);
		switch (SvTYPE(sref)) {
		case SVt_PVAV:
		    if (intro)
			SAVESPTR(GvAV(dstr));
		    else
			dref = (SV*)GvAV(dstr);
		    GvAV(dstr) = (AV*)sref;
		    if (PL_curcop->cop_stash != GvSTASH(dstr))
			GvIMPORTED_AV_on(dstr);
		    break;
		case SVt_PVHV:
		    if (intro)
			SAVESPTR(GvHV(dstr));
		    else
			dref = (SV*)GvHV(dstr);
		    GvHV(dstr) = (HV*)sref;
		    if (PL_curcop->cop_stash != GvSTASH(dstr))
			GvIMPORTED_HV_on(dstr);
		    break;
		case SVt_PVCV:
		    if (intro) {
			if (GvCVGEN(dstr) && GvCV(dstr) != (CV*)sref) {
			    SvREFCNT_dec(GvCV(dstr));
			    GvCV(dstr) = Nullcv;
			    GvCVGEN(dstr) = 0; /* Switch off cacheness. */
			    PL_sub_generation++;
			}
			SAVESPTR(GvCV(dstr));
		    }
		    else
			dref = (SV*)GvCV(dstr);
		    if (GvCV(dstr) != (CV*)sref) {
			CV* cv = GvCV(dstr);
			if (cv) {
			    if (!GvCVGEN((GV*)dstr) &&
				(CvROOT(cv) || CvXSUB(cv)))
			    {
				SV *const_sv = cv_const_sv(cv);
				bool const_changed = TRUE; 
				if(const_sv)
				    const_changed = sv_cmp(const_sv, 
					   op_const_sv(CvSTART((CV*)sref), 
						       Nullcv));
				/* ahem, death to those who redefine
				 * active sort subs */
				if (PL_curstackinfo->si_type == PERLSI_SORT &&
				      PL_sortcop == CvSTART(cv))
				    Perl_croak(aTHX_ 
				    "Can't redefine active sort subroutine %s",
					  GvENAME((GV*)dstr));
				if (ckWARN(WARN_REDEFINE) || (const_changed && const_sv)) {
				    if (!(CvGV(cv) && GvSTASH(CvGV(cv))
					  && HvNAME(GvSTASH(CvGV(cv)))
					  && strEQ(HvNAME(GvSTASH(CvGV(cv))),
						   "autouse")))
					Perl_warner(aTHX_ WARN_REDEFINE, const_sv ? 
					     "Constant subroutine %s redefined"
					     : "Subroutine %s redefined", 
					     GvENAME((GV*)dstr));
				}
			    }
			    cv_ckproto(cv, (GV*)dstr,
				       SvPOK(sref) ? SvPVX(sref) : Nullch);
			}
			GvCV(dstr) = (CV*)sref;
			GvCVGEN(dstr) = 0; /* Switch off cacheness. */
			GvASSUMECV_on(dstr);
			PL_sub_generation++;
		    }
		    if (PL_curcop->cop_stash != GvSTASH(dstr))
			GvIMPORTED_CV_on(dstr);
		    break;
		case SVt_PVIO:
		    if (intro)
			SAVESPTR(GvIOp(dstr));
		    else
			dref = (SV*)GvIOp(dstr);
		    GvIOp(dstr) = (IO*)sref;
		    break;
		default:
		    if (intro)
			SAVESPTR(GvSV(dstr));
		    else
			dref = (SV*)GvSV(dstr);
		    GvSV(dstr) = sref;
		    if (PL_curcop->cop_stash != GvSTASH(dstr))
			GvIMPORTED_SV_on(dstr);
		    break;
		}
		if (dref)
		    SvREFCNT_dec(dref);
		if (intro)
		    SAVEFREESV(sref);
		SvTAINT(dstr);
		return;
	    }
	    if (SvPVX(dstr)) {
		(void)SvOOK_off(dstr);		/* backoff */
		if (SvLEN(dstr))
		    Safefree(SvPVX(dstr));
		SvLEN(dstr)=SvCUR(dstr)=0;
	    }
	}
	(void)SvOK_off(dstr);
	SvRV(dstr) = SvREFCNT_inc(SvRV(sstr));
	SvROK_on(dstr);
	if (sflags & SVp_NOK) {
	    SvNOK_on(dstr);
	    SvNVX(dstr) = SvNVX(sstr);
	}
	if (sflags & SVp_IOK) {
	    (void)SvIOK_on(dstr);
	    SvIVX(dstr) = SvIVX(sstr);
	    if (SvIsUV(sstr))
		SvIsUV_on(dstr);
	}
	if (SvAMAGIC(sstr)) {
	    SvAMAGIC_on(dstr);
	}
    }
    else if (sflags & SVp_POK) {

	/*
	 * Check to see if we can just swipe the string.  If so, it's a
	 * possible small lose on short strings, but a big win on long ones.
	 * It might even be a win on short strings if SvPVX(dstr)
	 * has to be allocated and SvPVX(sstr) has to be freed.
	 */

	if (SvTEMP(sstr) &&		/* slated for free anyway? */
	    SvREFCNT(sstr) == 1 && 	/* and no other references to it? */
	    !(sflags & SVf_OOK)) 	/* and not involved in OOK hack? */
	{
	    if (SvPVX(dstr)) {		/* we know that dtype >= SVt_PV */
		if (SvOOK(dstr)) {
		    SvFLAGS(dstr) &= ~SVf_OOK;
		    Safefree(SvPVX(dstr) - SvIVX(dstr));
		}
		else if (SvLEN(dstr))
		    Safefree(SvPVX(dstr));
	    }
	    (void)SvPOK_only(dstr);
	    SvPV_set(dstr, SvPVX(sstr));
	    SvLEN_set(dstr, SvLEN(sstr));
	    SvCUR_set(dstr, SvCUR(sstr));
	    SvTEMP_off(dstr);
	    (void)SvOK_off(sstr);
	    SvPV_set(sstr, Nullch);
	    SvLEN_set(sstr, 0);
	    SvCUR_set(sstr, 0);
	    SvTEMP_off(sstr);
	}
	else {					/* have to copy actual string */
	    STRLEN len = SvCUR(sstr);

	    SvGROW(dstr, len + 1);		/* inlined from sv_setpvn */
	    Move(SvPVX(sstr),SvPVX(dstr),len,char);
	    SvCUR_set(dstr, len);
	    *SvEND(dstr) = '\0';
	    (void)SvPOK_only(dstr);
	}
	/*SUPPRESS 560*/
	if (sflags & SVp_NOK) {
	    SvNOK_on(dstr);
	    SvNVX(dstr) = SvNVX(sstr);
	}
	if (sflags & SVp_IOK) {
	    (void)SvIOK_on(dstr);
	    SvIVX(dstr) = SvIVX(sstr);
	    if (SvIsUV(sstr))
		SvIsUV_on(dstr);
	}
    }
    else if (sflags & SVp_NOK) {
	SvNVX(dstr) = SvNVX(sstr);
	(void)SvNOK_only(dstr);
	if (SvIOK(sstr)) {
	    (void)SvIOK_on(dstr);
	    SvIVX(dstr) = SvIVX(sstr);
	    /* XXXX Do we want to set IsUV for IV(ROK)?  Be extra safe... */
	    if (SvIsUV(sstr))
		SvIsUV_on(dstr);
	}
    }
    else if (sflags & SVp_IOK) {
	(void)SvIOK_only(dstr);
	SvIVX(dstr) = SvIVX(sstr);
	if (SvIsUV(sstr))
	    SvIsUV_on(dstr);
    }
    else {
	if (dtype == SVt_PVGV) {
	    if (ckWARN(WARN_UNSAFE))
		Perl_warner(aTHX_ WARN_UNSAFE, "Undefined value assigned to typeglob");
	}
	else
	    (void)SvOK_off(dstr);
    }
    SvTAINT(dstr);
}

void
Perl_sv_setsv_mg(pTHX_ SV *dstr, register SV *sstr)
{
    sv_setsv(dstr,sstr);
    SvSETMAGIC(dstr);
}

void
Perl_sv_setpvn(pTHX_ register SV *sv, register const char *ptr, register STRLEN len)
{
    register char *dptr;
    assert(len >= 0);  /* STRLEN is probably unsigned, so this may
			  elicit a warning, but it won't hurt. */
    SV_CHECK_THINKFIRST(sv);
    if (!ptr) {
	(void)SvOK_off(sv);
	return;
    }
    (void)SvUPGRADE(sv, SVt_PV);

    SvGROW(sv, len + 1);
    dptr = SvPVX(sv);
    Move(ptr,dptr,len,char);
    dptr[len] = '\0';
    SvCUR_set(sv, len);
    (void)SvPOK_only(sv);		/* validate pointer */
    SvTAINT(sv);
}

void
Perl_sv_setpvn_mg(pTHX_ register SV *sv, register const char *ptr, register STRLEN len)
{
    sv_setpvn(sv,ptr,len);
    SvSETMAGIC(sv);
}

void
Perl_sv_setpv(pTHX_ register SV *sv, register const char *ptr)
{
    register STRLEN len;

    SV_CHECK_THINKFIRST(sv);
    if (!ptr) {
	(void)SvOK_off(sv);
	return;
    }
    len = strlen(ptr);
    (void)SvUPGRADE(sv, SVt_PV);

    SvGROW(sv, len + 1);
    Move(ptr,SvPVX(sv),len+1,char);
    SvCUR_set(sv, len);
    (void)SvPOK_only(sv);		/* validate pointer */
    SvTAINT(sv);
}

void
Perl_sv_setpv_mg(pTHX_ register SV *sv, register const char *ptr)
{
    sv_setpv(sv,ptr);
    SvSETMAGIC(sv);
}

void
Perl_sv_usepvn(pTHX_ register SV *sv, register char *ptr, register STRLEN len)
{
    SV_CHECK_THINKFIRST(sv);
    (void)SvUPGRADE(sv, SVt_PV);
    if (!ptr) {
	(void)SvOK_off(sv);
	return;
    }
    (void)SvOOK_off(sv);
    if (SvPVX(sv) && SvLEN(sv))
	Safefree(SvPVX(sv));
    Renew(ptr, len+1, char);
    SvPVX(sv) = ptr;
    SvCUR_set(sv, len);
    SvLEN_set(sv, len+1);
    *SvEND(sv) = '\0';
    (void)SvPOK_only(sv);		/* validate pointer */
    SvTAINT(sv);
}

void
Perl_sv_usepvn_mg(pTHX_ register SV *sv, register char *ptr, register STRLEN len)
{
    sv_usepvn(sv,ptr,len);
    SvSETMAGIC(sv);
}

void
Perl_sv_force_normal(pTHX_ register SV *sv)
{
    if (SvREADONLY(sv)) {
	dTHR;
	if (PL_curcop != &PL_compiling)
	    Perl_croak(aTHX_ PL_no_modify);
    }
    if (SvROK(sv))
	sv_unref(sv);
    else if (SvFAKE(sv) && SvTYPE(sv) == SVt_PVGV)
	sv_unglob(sv);
}
    
void
Perl_sv_chop(pTHX_ register SV *sv, register char *ptr)	/* like set but assuming ptr is in sv */
                
                   
{
    register STRLEN delta;

    if (!ptr || !SvPOKp(sv))
	return;
    SV_CHECK_THINKFIRST(sv);
    if (SvTYPE(sv) < SVt_PVIV)
	sv_upgrade(sv,SVt_PVIV);

    if (!SvOOK(sv)) {
	if (!SvLEN(sv)) { /* make copy of shared string */
	    char *pvx = SvPVX(sv);
	    STRLEN len = SvCUR(sv);
	    SvGROW(sv, len + 1);
	    Move(pvx,SvPVX(sv),len,char);
	    *SvEND(sv) = '\0';
	}
	SvIVX(sv) = 0;
	SvFLAGS(sv) |= SVf_OOK;
    }
    SvFLAGS(sv) &= ~(SVf_IOK|SVf_NOK|SVp_IOK|SVp_NOK|SVf_IVisUV);
    delta = ptr - SvPVX(sv);
    SvLEN(sv) -= delta;
    SvCUR(sv) -= delta;
    SvPVX(sv) += delta;
    SvIVX(sv) += delta;
}

void
Perl_sv_catpvn(pTHX_ register SV *sv, register const char *ptr, register STRLEN len)
{
    STRLEN tlen;
    char *junk;

    junk = SvPV_force(sv, tlen);
    SvGROW(sv, tlen + len + 1);
    if (ptr == junk)
	ptr = SvPVX(sv);
    Move(ptr,SvPVX(sv)+tlen,len,char);
    SvCUR(sv) += len;
    *SvEND(sv) = '\0';
    (void)SvPOK_only(sv);		/* validate pointer */
    SvTAINT(sv);
}

void
Perl_sv_catpvn_mg(pTHX_ register SV *sv, register const char *ptr, register STRLEN len)
{
    sv_catpvn(sv,ptr,len);
    SvSETMAGIC(sv);
}

void
Perl_sv_catsv(pTHX_ SV *dstr, register SV *sstr)
{
    char *s;
    STRLEN len;
    if (!sstr)
	return;
    if (s = SvPV(sstr, len))
	sv_catpvn(dstr,s,len);
}

void
Perl_sv_catsv_mg(pTHX_ SV *dstr, register SV *sstr)
{
    sv_catsv(dstr,sstr);
    SvSETMAGIC(dstr);
}

void
Perl_sv_catpv(pTHX_ register SV *sv, register const char *ptr)
{
    register STRLEN len;
    STRLEN tlen;
    char *junk;

    if (!ptr)
	return;
    junk = SvPV_force(sv, tlen);
    len = strlen(ptr);
    SvGROW(sv, tlen + len + 1);
    if (ptr == junk)
	ptr = SvPVX(sv);
    Move(ptr,SvPVX(sv)+tlen,len+1,char);
    SvCUR(sv) += len;
    (void)SvPOK_only(sv);		/* validate pointer */
    SvTAINT(sv);
}

void
Perl_sv_catpv_mg(pTHX_ register SV *sv, register const char *ptr)
{
    sv_catpv(sv,ptr);
    SvSETMAGIC(sv);
}

SV *
Perl_newSV(pTHX_ STRLEN len)
{
    register SV *sv;
    
    new_SV(sv);
    if (len) {
	sv_upgrade(sv, SVt_PV);
	SvGROW(sv, len + 1);
    }
    return sv;
}

/* name is assumed to contain an SV* if (name && namelen == HEf_SVKEY) */

void
Perl_sv_magic(pTHX_ register SV *sv, SV *obj, int how, const char *name, I32 namlen)
{
    MAGIC* mg;
    
    if (SvREADONLY(sv)) {
	dTHR;
	if (PL_curcop != &PL_compiling && !strchr("gBf", how))
	    Perl_croak(aTHX_ PL_no_modify);
    }
    if (SvMAGICAL(sv) || (how == 't' && SvTYPE(sv) >= SVt_PVMG)) {
	if (SvMAGIC(sv) && (mg = mg_find(sv, how))) {
	    if (how == 't')
		mg->mg_len |= 1;
	    return;
	}
    }
    else {
        (void)SvUPGRADE(sv, SVt_PVMG);
    }
    Newz(702,mg, 1, MAGIC);
    mg->mg_moremagic = SvMAGIC(sv);

    SvMAGIC(sv) = mg;
    if (!obj || obj == sv || how == '#' || how == 'r')
	mg->mg_obj = obj;
    else {
	dTHR;
	mg->mg_obj = SvREFCNT_inc(obj);
	mg->mg_flags |= MGf_REFCOUNTED;
    }
    mg->mg_type = how;
    mg->mg_len = namlen;
    if (name)
	if (namlen >= 0)
	    mg->mg_ptr = savepvn(name, namlen);
	else if (namlen == HEf_SVKEY)
	    mg->mg_ptr = (char*)SvREFCNT_inc((SV*)name);
    
    switch (how) {
    case 0:
	mg->mg_virtual = &PL_vtbl_sv;
	break;
    case 'A':
        mg->mg_virtual = &PL_vtbl_amagic;
        break;
    case 'a':
        mg->mg_virtual = &PL_vtbl_amagicelem;
        break;
    case 'c':
        mg->mg_virtual = 0;
        break;
    case 'B':
	mg->mg_virtual = &PL_vtbl_bm;
	break;
    case 'D':
	mg->mg_virtual = &PL_vtbl_regdata;
	break;
    case 'd':
	mg->mg_virtual = &PL_vtbl_regdatum;
	break;
    case 'E':
	mg->mg_virtual = &PL_vtbl_env;
	break;
    case 'f':
	mg->mg_virtual = &PL_vtbl_fm;
	break;
    case 'e':
	mg->mg_virtual = &PL_vtbl_envelem;
	break;
    case 'g':
	mg->mg_virtual = &PL_vtbl_mglob;
	break;
    case 'I':
	mg->mg_virtual = &PL_vtbl_isa;
	break;
    case 'i':
	mg->mg_virtual = &PL_vtbl_isaelem;
	break;
    case 'k':
	mg->mg_virtual = &PL_vtbl_nkeys;
	break;
    case 'L':
	SvRMAGICAL_on(sv);
	mg->mg_virtual = 0;
	break;
    case 'l':
	mg->mg_virtual = &PL_vtbl_dbline;
	break;
#ifdef USE_THREADS
    case 'm':
	mg->mg_virtual = &PL_vtbl_mutex;
	break;
#endif /* USE_THREADS */
#ifdef USE_LOCALE_COLLATE
    case 'o':
        mg->mg_virtual = &PL_vtbl_collxfrm;
        break;
#endif /* USE_LOCALE_COLLATE */
    case 'P':
	mg->mg_virtual = &PL_vtbl_pack;
	break;
    case 'p':
    case 'q':
	mg->mg_virtual = &PL_vtbl_packelem;
	break;
    case 'r':
	mg->mg_virtual = &PL_vtbl_regexp;
	break;
    case 'S':
	mg->mg_virtual = &PL_vtbl_sig;
	break;
    case 's':
	mg->mg_virtual = &PL_vtbl_sigelem;
	break;
    case 't':
	mg->mg_virtual = &PL_vtbl_taint;
	mg->mg_len = 1;
	break;
    case 'U':
	mg->mg_virtual = &PL_vtbl_uvar;
	break;
    case 'v':
	mg->mg_virtual = &PL_vtbl_vec;
	break;
    case 'x':
	mg->mg_virtual = &PL_vtbl_substr;
	break;
    case 'y':
	mg->mg_virtual = &PL_vtbl_defelem;
	break;
    case '*':
	mg->mg_virtual = &PL_vtbl_glob;
	break;
    case '#':
	mg->mg_virtual = &PL_vtbl_arylen;
	break;
    case '.':
	mg->mg_virtual = &PL_vtbl_pos;
	break;
    case '<':
	mg->mg_virtual = &PL_vtbl_backref;
	break;
    case '~':	/* Reserved for use by extensions not perl internals.	*/
	/* Useful for attaching extension internal data to perl vars.	*/
	/* Note that multiple extensions may clash if magical scalars	*/
	/* etc holding private data from one are passed to another.	*/
	SvRMAGICAL_on(sv);
	break;
    default:
	Perl_croak(aTHX_ "Don't know how to handle magic of type '%c'", how);
    }
    mg_magical(sv);
    if (SvGMAGICAL(sv))
	SvFLAGS(sv) &= ~(SVf_IOK|SVf_NOK|SVf_POK);
}

int
Perl_sv_unmagic(pTHX_ SV *sv, int type)
{
    MAGIC* mg;
    MAGIC** mgp;
    if (SvTYPE(sv) < SVt_PVMG || !SvMAGIC(sv))
	return 0;
    mgp = &SvMAGIC(sv);
    for (mg = *mgp; mg; mg = *mgp) {
	if (mg->mg_type == type) {
	    MGVTBL* vtbl = mg->mg_virtual;
	    *mgp = mg->mg_moremagic;
	    if (vtbl && (vtbl->svt_free != NULL))
		CALL_FPTR(vtbl->svt_free)(aTHX_ sv, mg);
	    if (mg->mg_ptr && mg->mg_type != 'g')
		if (mg->mg_len >= 0)
		    Safefree(mg->mg_ptr);
		else if (mg->mg_len == HEf_SVKEY)
		    SvREFCNT_dec((SV*)mg->mg_ptr);
	    if (mg->mg_flags & MGf_REFCOUNTED)
		SvREFCNT_dec(mg->mg_obj);
	    Safefree(mg);
	}
	else
	    mgp = &mg->mg_moremagic;
    }
    if (!SvMAGIC(sv)) {
	SvMAGICAL_off(sv);
	SvFLAGS(sv) |= (SvFLAGS(sv) & (SVp_IOK|SVp_NOK|SVp_POK)) >> PRIVSHIFT;
    }

    return 0;
}

SV *
Perl_sv_rvweaken(pTHX_ SV *sv)
{
    SV *tsv;
    if (!SvOK(sv))  /* let undefs pass */
	return sv;
    if (!SvROK(sv))
	Perl_croak(aTHX_ "Can't weaken a nonreference");
    else if (SvWEAKREF(sv)) {
	dTHR;
	if (ckWARN(WARN_MISC))
	    Perl_warner(aTHX_ WARN_MISC, "Reference is already weak");
	return sv;
    }
    tsv = SvRV(sv);
    sv_add_backref(tsv, sv);
    SvWEAKREF_on(sv);
    SvREFCNT_dec(tsv);              
    return sv;
}

STATIC void
S_sv_add_backref(pTHX_ SV *tsv, SV *sv)
{
    AV *av;
    MAGIC *mg;
    if (SvMAGICAL(tsv) && (mg = mg_find(tsv, '<')))
	av = (AV*)mg->mg_obj;
    else {
	av = newAV();
	sv_magic(tsv, (SV*)av, '<', NULL, 0);
	SvREFCNT_dec(av);           /* for sv_magic */
    }
    av_push(av,sv);
}

STATIC void 
S_sv_del_backref(pTHX_ SV *sv)
{
    AV *av;
    SV **svp;
    I32 i;
    SV *tsv = SvRV(sv);
    MAGIC *mg;
    if (!SvMAGICAL(tsv) || !(mg = mg_find(tsv, '<')))
	Perl_croak(aTHX_ "panic: del_backref");
    av = (AV *)mg->mg_obj;
    svp = AvARRAY(av);
    i = AvFILLp(av);
    while (i >= 0) {
	if (svp[i] == sv) {
	    svp[i] = &PL_sv_undef; /* XXX */
	}
	i--;
    }
}

void
Perl_sv_insert(pTHX_ SV *bigstr, STRLEN offset, STRLEN len, char *little, STRLEN littlelen)
{
    register char *big;
    register char *mid;
    register char *midend;
    register char *bigend;
    register I32 i;
    STRLEN curlen;
    

    if (!bigstr)
	Perl_croak(aTHX_ "Can't modify non-existent substring");
    SvPV_force(bigstr, curlen);
    if (offset + len > curlen) {
	SvGROW(bigstr, offset+len+1);
	Zero(SvPVX(bigstr)+curlen, offset+len-curlen, char);
	SvCUR_set(bigstr, offset+len);
    }

    i = littlelen - len;
    if (i > 0) {			/* string might grow */
	big = SvGROW(bigstr, SvCUR(bigstr) + i + 1);
	mid = big + offset + len;
	midend = bigend = big + SvCUR(bigstr);
	bigend += i;
	*bigend = '\0';
	while (midend > mid)		/* shove everything down */
	    *--bigend = *--midend;
	Move(little,big+offset,littlelen,char);
	SvCUR(bigstr) += i;
	SvSETMAGIC(bigstr);
	return;
    }
    else if (i == 0) {
	Move(little,SvPVX(bigstr)+offset,len,char);
	SvSETMAGIC(bigstr);
	return;
    }

    big = SvPVX(bigstr);
    mid = big + offset;
    midend = mid + len;
    bigend = big + SvCUR(bigstr);

    if (midend > bigend)
	Perl_croak(aTHX_ "panic: sv_insert");

    if (mid - big > bigend - midend) {	/* faster to shorten from end */
	if (littlelen) {
	    Move(little, mid, littlelen,char);
	    mid += littlelen;
	}
	i = bigend - midend;
	if (i > 0) {
	    Move(midend, mid, i,char);
	    mid += i;
	}
	*mid = '\0';
	SvCUR_set(bigstr, mid - big);
    }
    /*SUPPRESS 560*/
    else if (i = mid - big) {	/* faster from front */
	midend -= littlelen;
	mid = midend;
	sv_chop(bigstr,midend-i);
	big += i;
	while (i--)
	    *--midend = *--big;
	if (littlelen)
	    Move(little, mid, littlelen,char);
    }
    else if (littlelen) {
	midend -= littlelen;
	sv_chop(bigstr,midend);
	Move(little,midend,littlelen,char);
    }
    else {
	sv_chop(bigstr,midend);
    }
    SvSETMAGIC(bigstr);
}

/* make sv point to what nstr did */

void
Perl_sv_replace(pTHX_ register SV *sv, register SV *nsv)
{
    dTHR;
    U32 refcnt = SvREFCNT(sv);
    SV_CHECK_THINKFIRST(sv);
    if (SvREFCNT(nsv) != 1 && ckWARN_d(WARN_INTERNAL))
	Perl_warner(aTHX_ WARN_INTERNAL, "Reference miscount in sv_replace()");
    if (SvMAGICAL(sv)) {
	if (SvMAGICAL(nsv))
	    mg_free(nsv);
	else
	    sv_upgrade(nsv, SVt_PVMG);
	SvMAGIC(nsv) = SvMAGIC(sv);
	SvFLAGS(nsv) |= SvMAGICAL(sv);
	SvMAGICAL_off(sv);
	SvMAGIC(sv) = 0;
    }
    SvREFCNT(sv) = 0;
    sv_clear(sv);
    assert(!SvREFCNT(sv));
    StructCopy(nsv,sv,SV);
    SvREFCNT(sv) = refcnt;
    SvFLAGS(nsv) |= SVTYPEMASK;		/* Mark as freed */
    del_SV(nsv);
}

void
Perl_sv_clear(pTHX_ register SV *sv)
{
    HV* stash;
    assert(sv);
    assert(SvREFCNT(sv) == 0);

    if (SvOBJECT(sv)) {
	dTHR;
	if (PL_defstash) {		/* Still have a symbol table? */
	    djSP;
	    GV* destructor;
	    SV tmpref;

	    Zero(&tmpref, 1, SV);
	    sv_upgrade(&tmpref, SVt_RV);
	    SvROK_on(&tmpref);
	    SvREADONLY_on(&tmpref);	/* DESTROY() could be naughty */
	    SvREFCNT(&tmpref) = 1;

	    do {
		stash = SvSTASH(sv);
		destructor = gv_fetchmethod(SvSTASH(sv), "DESTROY");
		if (destructor) {
		    ENTER;
		    PUSHSTACKi(PERLSI_DESTROY);
		    SvRV(&tmpref) = SvREFCNT_inc(sv);
		    EXTEND(SP, 2);
		    PUSHMARK(SP);
		    PUSHs(&tmpref);
		    PUTBACK;
		    call_sv((SV*)GvCV(destructor),
			    G_DISCARD|G_EVAL|G_KEEPERR);
		    SvREFCNT(sv)--;
		    POPSTACK;
		    SPAGAIN;
		    LEAVE;
		}
	    } while (SvOBJECT(sv) && SvSTASH(sv) != stash);

	    del_XRV(SvANY(&tmpref));

	    if (SvREFCNT(sv)) {
		if (PL_in_clean_objs)
		    Perl_croak(aTHX_ "DESTROY created new reference to dead object '%s'",
			  HvNAME(stash));
		/* DESTROY gave object new lease on life */
		return;
	    }
	}

	if (SvOBJECT(sv)) {
	    SvREFCNT_dec(SvSTASH(sv));	/* possibly of changed persuasion */
	    SvOBJECT_off(sv);	/* Curse the object. */
	    if (SvTYPE(sv) != SVt_PVIO)
		--PL_sv_objcount;	/* XXX Might want something more general */
	}
    }
    if (SvTYPE(sv) >= SVt_PVMG && SvMAGIC(sv))
	mg_free(sv);
    stash = NULL;
    switch (SvTYPE(sv)) {
    case SVt_PVIO:
	if (IoIFP(sv) &&
	    IoIFP(sv) != PerlIO_stdin() &&
	    IoIFP(sv) != PerlIO_stdout() &&
	    IoIFP(sv) != PerlIO_stderr())
	{
	    io_close((IO*)sv, FALSE);
	}
	if (IoDIRP(sv)) {
	    PerlDir_close(IoDIRP(sv));
	    IoDIRP(sv) = 0;
	}
	Safefree(IoTOP_NAME(sv));
	Safefree(IoFMT_NAME(sv));
	Safefree(IoBOTTOM_NAME(sv));
	/* FALL THROUGH */
    case SVt_PVBM:
	goto freescalar;
    case SVt_PVCV:
    case SVt_PVFM:
	cv_undef((CV*)sv);
	goto freescalar;
    case SVt_PVHV:
	hv_undef((HV*)sv);
	break;
    case SVt_PVAV:
	av_undef((AV*)sv);
	break;
    case SVt_PVLV:
	SvREFCNT_dec(LvTARG(sv));
	goto freescalar;
    case SVt_PVGV:
	gp_free((GV*)sv);
	Safefree(GvNAME(sv));
	/* cannot decrease stash refcount yet, as we might recursively delete
	   ourselves when the refcnt drops to zero. Delay SvREFCNT_dec
	   of stash until current sv is completely gone.
	   -- JohnPC, 27 Mar 1998 */
	stash = GvSTASH(sv);
	/* FALL THROUGH */
    case SVt_PVMG:
    case SVt_PVNV:
    case SVt_PVIV:
      freescalar:
	(void)SvOOK_off(sv);
	/* FALL THROUGH */
    case SVt_PV:
    case SVt_RV:
	if (SvROK(sv)) {
	    if (SvWEAKREF(sv))
	        sv_del_backref(sv);
	    else
	        SvREFCNT_dec(SvRV(sv));
	}
	else if (SvPVX(sv) && SvLEN(sv))
	    Safefree(SvPVX(sv));
	break;
/*
    case SVt_NV:
    case SVt_IV:
    case SVt_NULL:
	break;
*/
    }

    switch (SvTYPE(sv)) {
    case SVt_NULL:
	break;
    case SVt_IV:
	del_XIV(SvANY(sv));
	break;
    case SVt_NV:
	del_XNV(SvANY(sv));
	break;
    case SVt_RV:
	del_XRV(SvANY(sv));
	break;
    case SVt_PV:
	del_XPV(SvANY(sv));
	break;
    case SVt_PVIV:
	del_XPVIV(SvANY(sv));
	break;
    case SVt_PVNV:
	del_XPVNV(SvANY(sv));
	break;
    case SVt_PVMG:
	del_XPVMG(SvANY(sv));
	break;
    case SVt_PVLV:
	del_XPVLV(SvANY(sv));
	break;
    case SVt_PVAV:
	del_XPVAV(SvANY(sv));
	break;
    case SVt_PVHV:
	del_XPVHV(SvANY(sv));
	break;
    case SVt_PVCV:
	del_XPVCV(SvANY(sv));
	break;
    case SVt_PVGV:
	del_XPVGV(SvANY(sv));
	/* code duplication for increased performance. */
	SvFLAGS(sv) &= SVf_BREAK;
	SvFLAGS(sv) |= SVTYPEMASK;
	/* decrease refcount of the stash that owns this GV, if any */
	if (stash)
	    SvREFCNT_dec(stash);
	return; /* not break, SvFLAGS reset already happened */
    case SVt_PVBM:
	del_XPVBM(SvANY(sv));
	break;
    case SVt_PVFM:
	del_XPVFM(SvANY(sv));
	break;
    case SVt_PVIO:
	del_XPVIO(SvANY(sv));
	break;
    }
    SvFLAGS(sv) &= SVf_BREAK;
    SvFLAGS(sv) |= SVTYPEMASK;
}

SV *
Perl_sv_newref(pTHX_ SV *sv)
{
    if (sv)
	ATOMIC_INC(SvREFCNT(sv));
    return sv;
}

void
Perl_sv_free(pTHX_ SV *sv)
{
    dTHR;
    int refcount_is_zero;

    if (!sv)
	return;
    if (SvREFCNT(sv) == 0) {
	if (SvFLAGS(sv) & SVf_BREAK)
	    return;
	if (PL_in_clean_all) /* All is fair */
	    return;
	if (SvREADONLY(sv) && SvIMMORTAL(sv)) {
	    /* make sure SvREFCNT(sv)==0 happens very seldom */
	    SvREFCNT(sv) = (~(U32)0)/2;
	    return;
	}
	if (ckWARN_d(WARN_INTERNAL))
	    Perl_warner(aTHX_ WARN_INTERNAL, "Attempt to free unreferenced scalar");
	return;
    }
    ATOMIC_DEC_AND_TEST(refcount_is_zero, SvREFCNT(sv));
    if (!refcount_is_zero)
	return;
#ifdef DEBUGGING
    if (SvTEMP(sv)) {
	if (ckWARN_d(WARN_DEBUGGING))
	    Perl_warner(aTHX_ WARN_DEBUGGING,
			"Attempt to free temp prematurely: SV 0x%lx", (unsigned long)sv);
	return;
    }
#endif
    if (SvREADONLY(sv) && SvIMMORTAL(sv)) {
	/* make sure SvREFCNT(sv)==0 happens very seldom */
	SvREFCNT(sv) = (~(U32)0)/2;
	return;
    }
    sv_clear(sv);
    if (! SvREFCNT(sv))
	del_SV(sv);
}

STRLEN
Perl_sv_len(pTHX_ register SV *sv)
{
    char *junk;
    STRLEN len;

    if (!sv)
	return 0;

    if (SvGMAGICAL(sv))
	len = mg_length(sv);
    else
	junk = SvPV(sv, len);
    return len;
}

STRLEN
Perl_sv_len_utf8(pTHX_ register SV *sv)
{
    U8 *s;
    U8 *send;
    STRLEN len;

    if (!sv)
	return 0;

#ifdef NOTYET
    if (SvGMAGICAL(sv))
	len = mg_length(sv);
    else
#endif
	s = (U8*)SvPV(sv, len);
    send = s + len;
    len = 0;
    while (s < send) {
	s += UTF8SKIP(s);
	len++;
    }
    return len;
}

void
Perl_sv_pos_u2b(pTHX_ register SV *sv, I32* offsetp, I32* lenp)
{
    U8 *start;
    U8 *s;
    U8 *send;
    I32 uoffset = *offsetp;
    STRLEN len;

    if (!sv)
	return;

    start = s = (U8*)SvPV(sv, len);
    send = s + len;
    while (s < send && uoffset--)
	s += UTF8SKIP(s);
    if (s >= send)
	s = send;
    *offsetp = s - start;
    if (lenp) {
	I32 ulen = *lenp;
	start = s;
	while (s < send && ulen--)
	    s += UTF8SKIP(s);
	if (s >= send)
	    s = send;
	*lenp = s - start;
    }
    return;
}

void
Perl_sv_pos_b2u(pTHX_ register SV *sv, I32* offsetp)
{
    U8 *s;
    U8 *send;
    STRLEN len;

    if (!sv)
	return;

    s = (U8*)SvPV(sv, len);
    if (len < *offsetp)
	Perl_croak(aTHX_ "panic: bad byte offset");
    send = s + *offsetp;
    len = 0;
    while (s < send) {
	s += UTF8SKIP(s);
	++len;
    }
    if (s != send) {
        dTHR;
	if (ckWARN_d(WARN_UTF8))    
	    Perl_warner(aTHX_ WARN_UTF8, "Malformed UTF-8 character");
	--len;
    }
    *offsetp = len;
    return;
}

I32
Perl_sv_eq(pTHX_ register SV *str1, register SV *str2)
{
    char *pv1;
    STRLEN cur1;
    char *pv2;
    STRLEN cur2;

    if (!str1) {
	pv1 = "";
	cur1 = 0;
    }
    else
	pv1 = SvPV(str1, cur1);

    if (!str2)
	return !cur1;
    else
	pv2 = SvPV(str2, cur2);

    if (cur1 != cur2)
	return 0;

    return memEQ(pv1, pv2, cur1);
}

I32
Perl_sv_cmp(pTHX_ register SV *str1, register SV *str2)
{
    STRLEN cur1 = 0;
    char *pv1 = str1 ? SvPV(str1, cur1) : (char *) NULL;
    STRLEN cur2 = 0;
    char *pv2 = str2 ? SvPV(str2, cur2) : (char *) NULL;
    I32 retval;

    if (!cur1)
	return cur2 ? -1 : 0;

    if (!cur2)
	return 1;

    retval = memcmp((void*)pv1, (void*)pv2, cur1 < cur2 ? cur1 : cur2);

    if (retval)
	return retval < 0 ? -1 : 1;

    if (cur1 == cur2)
	return 0;
    else
	return cur1 < cur2 ? -1 : 1;
}

I32
Perl_sv_cmp_locale(pTHX_ register SV *sv1, register SV *sv2)
{
#ifdef USE_LOCALE_COLLATE

    char *pv1, *pv2;
    STRLEN len1, len2;
    I32 retval;

    if (PL_collation_standard)
	goto raw_compare;

    len1 = 0;
    pv1 = sv1 ? sv_collxfrm(sv1, &len1) : (char *) NULL;
    len2 = 0;
    pv2 = sv2 ? sv_collxfrm(sv2, &len2) : (char *) NULL;

    if (!pv1 || !len1) {
	if (pv2 && len2)
	    return -1;
	else
	    goto raw_compare;
    }
    else {
	if (!pv2 || !len2)
	    return 1;
    }

    retval = memcmp((void*)pv1, (void*)pv2, len1 < len2 ? len1 : len2);

    if (retval)
	return retval < 0 ? -1 : 1;

    /*
     * When the result of collation is equality, that doesn't mean
     * that there are no differences -- some locales exclude some
     * characters from consideration.  So to avoid false equalities,
     * we use the raw string as a tiebreaker.
     */

  raw_compare:
    /* FALL THROUGH */

#endif /* USE_LOCALE_COLLATE */

    return sv_cmp(sv1, sv2);
}

#ifdef USE_LOCALE_COLLATE
/*
 * Any scalar variable may carry an 'o' magic that contains the
 * scalar data of the variable transformed to such a format that
 * a normal memory comparison can be used to compare the data
 * according to the locale settings.
 */
char *
Perl_sv_collxfrm(pTHX_ SV *sv, STRLEN *nxp)
{
    MAGIC *mg;

    mg = SvMAGICAL(sv) ? mg_find(sv, 'o') : (MAGIC *) NULL;
    if (!mg || !mg->mg_ptr || *(U32*)mg->mg_ptr != PL_collation_ix) {
	char *s, *xf;
	STRLEN len, xlen;

	if (mg)
	    Safefree(mg->mg_ptr);
	s = SvPV(sv, len);
	if ((xf = mem_collxfrm(s, len, &xlen))) {
	    if (SvREADONLY(sv)) {
		SAVEFREEPV(xf);
		*nxp = xlen;
		return xf + sizeof(PL_collation_ix);
	    }
	    if (! mg) {
		sv_magic(sv, 0, 'o', 0, 0);
		mg = mg_find(sv, 'o');
		assert(mg);
	    }
	    mg->mg_ptr = xf;
	    mg->mg_len = xlen;
	}
	else {
	    if (mg) {
		mg->mg_ptr = NULL;
		mg->mg_len = -1;
	    }
	}
    }
    if (mg && mg->mg_ptr) {
	*nxp = mg->mg_len;
	return mg->mg_ptr + sizeof(PL_collation_ix);
    }
    else {
	*nxp = 0;
	return NULL;
    }
}

#endif /* USE_LOCALE_COLLATE */

char *
Perl_sv_gets(pTHX_ register SV *sv, register PerlIO *fp, I32 append)
{
    dTHR;
    char *rsptr;
    STRLEN rslen;
    register STDCHAR rslast;
    register STDCHAR *bp;
    register I32 cnt;
    I32 i;

    SV_CHECK_THINKFIRST(sv);
    (void)SvUPGRADE(sv, SVt_PV);

    SvSCREAM_off(sv);

    if (RsSNARF(PL_rs)) {
	rsptr = NULL;
	rslen = 0;
    }
    else if (RsRECORD(PL_rs)) {
      I32 recsize, bytesread;
      char *buffer;

      /* Grab the size of the record we're getting */
      recsize = SvIV(SvRV(PL_rs));
      (void)SvPOK_only(sv);    /* Validate pointer */
      buffer = SvGROW(sv, recsize + 1);
      /* Go yank in */
#ifdef VMS
      /* VMS wants read instead of fread, because fread doesn't respect */
      /* RMS record boundaries. This is not necessarily a good thing to be */
      /* doing, but we've got no other real choice */
      bytesread = PerlLIO_read(PerlIO_fileno(fp), buffer, recsize);
#else
      bytesread = PerlIO_read(fp, buffer, recsize);
#endif
      SvCUR_set(sv, bytesread);
      buffer[bytesread] = '\0';
      return(SvCUR(sv) ? SvPVX(sv) : Nullch);
    }
    else if (RsPARA(PL_rs)) {
	rsptr = "\n\n";
	rslen = 2;
    }
    else
	rsptr = SvPV(PL_rs, rslen);
    rslast = rslen ? rsptr[rslen - 1] : '\0';

    if (RsPARA(PL_rs)) {		/* have to do this both before and after */
	do {			/* to make sure file boundaries work right */
	    if (PerlIO_eof(fp))
		return 0;
	    i = PerlIO_getc(fp);
	    if (i != '\n') {
		if (i == -1)
		    return 0;
		PerlIO_ungetc(fp,i);
		break;
	    }
	} while (i != EOF);
    }

    /* See if we know enough about I/O mechanism to cheat it ! */

    /* This used to be #ifdef test - it is made run-time test for ease
       of abstracting out stdio interface. One call should be cheap 
       enough here - and may even be a macro allowing compile
       time optimization.
     */

    if (PerlIO_fast_gets(fp)) {

    /*
     * We're going to steal some values from the stdio struct
     * and put EVERYTHING in the innermost loop into registers.
     */
    register STDCHAR *ptr;
    STRLEN bpx;
    I32 shortbuffered;

#if defined(VMS) && defined(PERLIO_IS_STDIO)
    /* An ungetc()d char is handled separately from the regular
     * buffer, so we getc() it back out and stuff it in the buffer.
     */
    i = PerlIO_getc(fp);
    if (i == EOF) return 0;
    *(--((*fp)->_ptr)) = (unsigned char) i;
    (*fp)->_cnt++;
#endif

    /* Here is some breathtakingly efficient cheating */

    cnt = PerlIO_get_cnt(fp);			/* get count into register */
    (void)SvPOK_only(sv);		/* validate pointer */
    if (SvLEN(sv) - append <= cnt + 1) { /* make sure we have the room */
	if (cnt > 80 && SvLEN(sv) > append) {
	    shortbuffered = cnt - SvLEN(sv) + append + 1;
	    cnt -= shortbuffered;
	}
	else {
	    shortbuffered = 0;
	    /* remember that cnt can be negative */
	    SvGROW(sv, append + (cnt <= 0 ? 2 : (cnt + 1)));
	}
    }
    else
	shortbuffered = 0;
    bp = (STDCHAR*)SvPVX(sv) + append;  /* move these two too to registers */
    ptr = (STDCHAR*)PerlIO_get_ptr(fp);
    DEBUG_P(PerlIO_printf(Perl_debug_log,
	"Screamer: entering, ptr=%ld, cnt=%ld\n",(long)ptr,(long)cnt));
    DEBUG_P(PerlIO_printf(Perl_debug_log,
	"Screamer: entering: FILE * thinks ptr=%ld, cnt=%ld, base=%ld\n",
	       (long)PerlIO_get_ptr(fp), (long)PerlIO_get_cnt(fp), 
	       (long)(PerlIO_has_base(fp) ? PerlIO_get_base(fp) : 0)));
    for (;;) {
      screamer:
	if (cnt > 0) {
	    if (rslen) {
		while (cnt > 0) {		     /* this     |  eat */
		    cnt--;
		    if ((*bp++ = *ptr++) == rslast)  /* really   |  dust */
			goto thats_all_folks;	     /* screams  |  sed :-) */
		}
	    }
	    else {
	        Copy(ptr, bp, cnt, char);	     /* this     |  eat */    
		bp += cnt;			     /* screams  |  dust */   
		ptr += cnt;			     /* louder   |  sed :-) */
		cnt = 0;
	    }
	}
	
	if (shortbuffered) {		/* oh well, must extend */
	    cnt = shortbuffered;
	    shortbuffered = 0;
	    bpx = bp - (STDCHAR*)SvPVX(sv); /* box up before relocation */
	    SvCUR_set(sv, bpx);
	    SvGROW(sv, SvLEN(sv) + append + cnt + 2);
	    bp = (STDCHAR*)SvPVX(sv) + bpx; /* unbox after relocation */
	    continue;
	}

	DEBUG_P(PerlIO_printf(Perl_debug_log,
	    "Screamer: going to getc, ptr=%ld, cnt=%ld\n",(long)ptr,(long)cnt));
	PerlIO_set_ptrcnt(fp, ptr, cnt); /* deregisterize cnt and ptr */
	DEBUG_P(PerlIO_printf(Perl_debug_log,
	    "Screamer: pre: FILE * thinks ptr=%ld, cnt=%ld, base=%ld\n",
	    (long)PerlIO_get_ptr(fp), (long)PerlIO_get_cnt(fp), 
	    (long)(PerlIO_has_base (fp) ? PerlIO_get_base(fp) : 0)));
	/* This used to call 'filbuf' in stdio form, but as that behaves like 
	   getc when cnt <= 0 we use PerlIO_getc here to avoid introducing
	   another abstraction.  */
	i   = PerlIO_getc(fp);		/* get more characters */
	DEBUG_P(PerlIO_printf(Perl_debug_log,
	    "Screamer: post: FILE * thinks ptr=%ld, cnt=%ld, base=%ld\n",
	    (long)PerlIO_get_ptr(fp), (long)PerlIO_get_cnt(fp), 
	    (long)(PerlIO_has_base (fp) ? PerlIO_get_base(fp) : 0)));
	cnt = PerlIO_get_cnt(fp);
	ptr = (STDCHAR*)PerlIO_get_ptr(fp);	/* reregisterize cnt and ptr */
	DEBUG_P(PerlIO_printf(Perl_debug_log,
	    "Screamer: after getc, ptr=%ld, cnt=%ld\n",(long)ptr,(long)cnt));

	if (i == EOF)			/* all done for ever? */
	    goto thats_really_all_folks;

	bpx = bp - (STDCHAR*)SvPVX(sv);	/* box up before relocation */
	SvCUR_set(sv, bpx);
	SvGROW(sv, bpx + cnt + 2);
	bp = (STDCHAR*)SvPVX(sv) + bpx;	/* unbox after relocation */

	*bp++ = i;			/* store character from PerlIO_getc */

	if (rslen && (STDCHAR)i == rslast)  /* all done for now? */
	    goto thats_all_folks;
    }

thats_all_folks:
    if ((rslen > 1 && (bp - (STDCHAR*)SvPVX(sv) < rslen)) ||
	  memNE((char*)bp - rslen, rsptr, rslen))
	goto screamer;				/* go back to the fray */
thats_really_all_folks:
    if (shortbuffered)
	cnt += shortbuffered;
	DEBUG_P(PerlIO_printf(Perl_debug_log,
	    "Screamer: quitting, ptr=%ld, cnt=%ld\n",(long)ptr,(long)cnt));
    PerlIO_set_ptrcnt(fp, ptr, cnt);	/* put these back or we're in trouble */
    DEBUG_P(PerlIO_printf(Perl_debug_log,
	"Screamer: end: FILE * thinks ptr=%ld, cnt=%ld, base=%ld\n",
	(long)PerlIO_get_ptr(fp), (long)PerlIO_get_cnt(fp), 
	(long)(PerlIO_has_base (fp) ? PerlIO_get_base(fp) : 0)));
    *bp = '\0';