[p5sagit/p5-mst-13.2.git] / gv.c

/*    gv.c
 *
 *    Copyright (c) 1991-2002, 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.
 *
 */

/*
 *   'Mercy!' cried Gandalf.  'If the giving of information is to be the cure
 * of your inquisitiveness, I shall spend all the rest of my days answering
 * you.  What more do you want to know?'
 *   'The names of all the stars, and of all living things, and the whole
 * history of Middle-earth and Over-heaven and of the Sundering Seas,'
 * laughed Pippin.
 */

/*
=head1 GV Functions
*/

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

GV *
Perl_gv_AVadd(pTHX_ register GV *gv)
{
    if (!gv || SvTYPE((SV*)gv) != SVt_PVGV)
	Perl_croak(aTHX_ "Bad symbol for array");
    if (!GvAV(gv))
	GvAV(gv) = newAV();
    return gv;
}

GV *
Perl_gv_HVadd(pTHX_ register GV *gv)
{
    if (!gv || SvTYPE((SV*)gv) != SVt_PVGV)
	Perl_croak(aTHX_ "Bad symbol for hash");
    if (!GvHV(gv))
	GvHV(gv) = newHV();
    return gv;
}

GV *
Perl_gv_IOadd(pTHX_ register GV *gv)
{
    if (!gv || SvTYPE((SV*)gv) != SVt_PVGV)
	Perl_croak(aTHX_ "Bad symbol for filehandle");
    if (!GvIOp(gv)) {
#ifdef GV_UNIQUE_CHECK
        if (GvUNIQUE(gv)) {
            Perl_croak(aTHX_ "Bad symbol for filehandle (GV is unique)");
        }
#endif
	GvIOp(gv) = newIO();
    }
    return gv;
}

GV *
Perl_gv_fetchfile(pTHX_ const char *name)
{
    char smallbuf[256];
    char *tmpbuf;
    STRLEN tmplen;
    GV *gv;

    if (!PL_defstash)
	return Nullgv;

    tmplen = strlen(name) + 2;
    if (tmplen < sizeof smallbuf)
	tmpbuf = smallbuf;
    else
	New(603, tmpbuf, tmplen + 1, char);
    /* This is where the debugger's %{"::_<$filename"} hash is created */
    tmpbuf[0] = '_';
    tmpbuf[1] = '<';
    strcpy(tmpbuf + 2, name);
    gv = *(GV**)hv_fetch(PL_defstash, tmpbuf, tmplen, TRUE);
    if (!isGV(gv)) {
	gv_init(gv, PL_defstash, tmpbuf, tmplen, FALSE);
	sv_setpv(GvSV(gv), name);
	if (PERLDB_LINE)
	    hv_magic(GvHVn(gv_AVadd(gv)), Nullgv, PERL_MAGIC_dbfile);
    }
    if (tmpbuf != smallbuf)
	Safefree(tmpbuf);
    return gv;
}

void
Perl_gv_init(pTHX_ GV *gv, HV *stash, const char *name, STRLEN len, int multi)
{
    register GP *gp;
    bool doproto = SvTYPE(gv) > SVt_NULL;
    char *proto = (doproto && SvPOK(gv)) ? SvPVX(gv) : NULL;

    sv_upgrade((SV*)gv, SVt_PVGV);
    if (SvLEN(gv)) {
	if (proto) {
	    SvPVX(gv) = NULL;
	    SvLEN(gv) = 0;
	    SvPOK_off(gv);
	} else
	    Safefree(SvPVX(gv));
    }
    Newz(602, gp, 1, GP);
    GvGP(gv) = gp_ref(gp);
    GvSV(gv) = NEWSV(72,0);
    GvLINE(gv) = CopLINE(PL_curcop);
    GvFILE(gv) = CopFILE(PL_curcop) ? CopFILE(PL_curcop) : "";
    GvCVGEN(gv) = 0;
    GvEGV(gv) = gv;
    sv_magic((SV*)gv, (SV*)gv, PERL_MAGIC_glob, Nullch, 0);
    GvSTASH(gv) = (HV*)SvREFCNT_inc(stash);
    GvNAME(gv) = savepvn(name, len);
    GvNAMELEN(gv) = len;
    if (multi || doproto)              /* doproto means it _was_ mentioned */
	GvMULTI_on(gv);
    if (doproto) {			/* Replicate part of newSUB here. */
	SvIOK_off(gv);
	ENTER;
	/* XXX unsafe for threads if eval_owner isn't held */
	start_subparse(0,0);		/* Create CV in compcv. */
	GvCV(gv) = PL_compcv;
	LEAVE;

	PL_sub_generation++;
	CvGV(GvCV(gv)) = gv;
	CvFILE_set_from_cop(GvCV(gv), PL_curcop);
	CvSTASH(GvCV(gv)) = PL_curstash;
#ifdef USE_5005THREADS
	CvOWNER(GvCV(gv)) = 0;
	if (!CvMUTEXP(GvCV(gv))) {
	    New(666, CvMUTEXP(GvCV(gv)), 1, perl_mutex);
	    MUTEX_INIT(CvMUTEXP(GvCV(gv)));
	}
#endif /* USE_5005THREADS */
	if (proto) {
	    sv_setpv((SV*)GvCV(gv), proto);
	    Safefree(proto);
	}
    }
}

STATIC void
S_gv_init_sv(pTHX_ GV *gv, I32 sv_type)
{
    switch (sv_type) {
    case SVt_PVIO:
	(void)GvIOn(gv);
	break;
    case SVt_PVAV:
	(void)GvAVn(gv);
	break;
    case SVt_PVHV:
	(void)GvHVn(gv);
	break;
    }
}

/*
=for apidoc gv_fetchmeth

Returns the glob with the given C<name> and a defined subroutine or
C<NULL>.  The glob lives in the given C<stash>, or in the stashes
accessible via @ISA and UNIVERSAL::.

The argument C<level> should be either 0 or -1.  If C<level==0>, as a
side-effect creates a glob with the given C<name> in the given C<stash>
which in the case of success contains an alias for the subroutine, and sets
up caching info for this glob.  Similarly for all the searched stashes.

This function grants C<"SUPER"> token as a postfix of the stash name. The
GV returned from C<gv_fetchmeth> may be a method cache entry, which is not
visible to Perl code.  So when calling C<call_sv>, you should not use
the GV directly; instead, you should use the method's CV, which can be
obtained from the GV with the C<GvCV> macro.

=cut
*/

GV *
Perl_gv_fetchmeth(pTHX_ HV *stash, const char *name, STRLEN len, I32 level)
{
    AV* av;
    GV* topgv;
    GV* gv;
    GV** gvp;
    CV* cv;

    /* UNIVERSAL methods should be callable without a stash */
    if (!stash) {
	level = -1;  /* probably appropriate */
	if(!(stash = gv_stashpvn("UNIVERSAL", 9, FALSE)))
	    return 0;
    }

    if ((level > 100) || (level < -100))
	Perl_croak(aTHX_ "Recursive inheritance detected while looking for method '%s' in package '%s'",
	      name, HvNAME(stash));

    DEBUG_o( Perl_deb(aTHX_ "Looking for method %s in package %s\n",name,HvNAME(stash)) );

    gvp = (GV**)hv_fetch(stash, name, len, (level >= 0));
    if (!gvp)
	topgv = Nullgv;
    else {
	topgv = *gvp;
	if (SvTYPE(topgv) != SVt_PVGV)
	    gv_init(topgv, stash, name, len, TRUE);
	if ((cv = GvCV(topgv))) {
	    /* If genuine method or valid cache entry, use it */
	    if (!GvCVGEN(topgv) || GvCVGEN(topgv) == PL_sub_generation)
		return topgv;
	    /* Stale cached entry: junk it */
	    SvREFCNT_dec(cv);
	    GvCV(topgv) = cv = Nullcv;
	    GvCVGEN(topgv) = 0;
	}
	else if (GvCVGEN(topgv) == PL_sub_generation)
	    return 0;  /* cache indicates sub doesn't exist */
    }

    gvp = (GV**)hv_fetch(stash, "ISA", 3, FALSE);
    av = (gvp && (gv = *gvp) && gv != (GV*)&PL_sv_undef) ? GvAV(gv) : Nullav;

    /* create and re-create @.*::SUPER::ISA on demand */
    if (!av || !SvMAGIC(av)) {
	char* packname = HvNAME(stash);
	STRLEN packlen = strlen(packname);

	if (packlen >= 7 && strEQ(packname + packlen - 7, "::SUPER")) {
	    HV* basestash;

	    packlen -= 7;
	    basestash = gv_stashpvn(packname, packlen, TRUE);
	    gvp = (GV**)hv_fetch(basestash, "ISA", 3, FALSE);
	    if (gvp && (gv = *gvp) != (GV*)&PL_sv_undef && (av = GvAV(gv))) {
		gvp = (GV**)hv_fetch(stash, "ISA", 3, TRUE);
		if (!gvp || !(gv = *gvp))
		    Perl_croak(aTHX_ "Cannot create %s::ISA", HvNAME(stash));
		if (SvTYPE(gv) != SVt_PVGV)
		    gv_init(gv, stash, "ISA", 3, TRUE);
		SvREFCNT_dec(GvAV(gv));
		GvAV(gv) = (AV*)SvREFCNT_inc(av);
	    }
	}
    }

    if (av) {
	SV** svp = AvARRAY(av);
	/* NOTE: No support for tied ISA */
	I32 items = AvFILLp(av) + 1;
	while (items--) {
	    SV* sv = *svp++;
	    HV* basestash = gv_stashsv(sv, FALSE);
	    if (!basestash) {
		if (ckWARN(WARN_MISC))
		    Perl_warner(aTHX_ packWARN(WARN_MISC), "Can't locate package %s for @%s::ISA",
			SvPVX(sv), HvNAME(stash));
		continue;
	    }
	    gv = gv_fetchmeth(basestash, name, len,
			      (level >= 0) ? level + 1 : level - 1);
	    if (gv)
		goto gotcha;
	}
    }

    /* if at top level, try UNIVERSAL */

    if (level == 0 || level == -1) {
	HV* lastchance;

	if ((lastchance = gv_stashpvn("UNIVERSAL", 9, FALSE))) {
	    if ((gv = gv_fetchmeth(lastchance, name, len,
				  (level >= 0) ? level + 1 : level - 1)))
	    {
	  gotcha:
		/*
		 * Cache method in topgv if:
		 *  1. topgv has no synonyms (else inheritance crosses wires)
		 *  2. method isn't a stub (else AUTOLOAD fails spectacularly)
		 */
		if (topgv &&
		    GvREFCNT(topgv) == 1 &&
		    (cv = GvCV(gv)) &&
		    (CvROOT(cv) || CvXSUB(cv)))
		{
		    if ((cv = GvCV(topgv)))
			SvREFCNT_dec(cv);
		    GvCV(topgv) = (CV*)SvREFCNT_inc(GvCV(gv));
		    GvCVGEN(topgv) = PL_sub_generation;
		}
		return gv;
	    }
	    else if (topgv && GvREFCNT(topgv) == 1) {
		/* cache the fact that the method is not defined */
		GvCVGEN(topgv) = PL_sub_generation;
	    }
	}
    }

    return 0;
}

/*
=for apidoc gv_fetchmeth_autoload

Same as gv_fetchmeth(), but looks for autoloaded subroutines too.
Returns a glob for the subroutine.

For an autoloaded subroutine without a GV, will create a GV even
if C<level < 0>.  For an autoloaded subroutine without a stub, GvCV()
of the result may be zero.

=cut
*/

GV *
Perl_gv_fetchmeth_autoload(pTHX_ HV *stash, const char *name, STRLEN len, I32 level)
{
    GV *gv = gv_fetchmeth(stash, name, len, level);

    if (!gv) {
	char autoload[] = "AUTOLOAD";
	STRLEN autolen = sizeof(autoload)-1;
	CV *cv;
	GV **gvp;

	if (!stash)
	    return Nullgv;	/* UNIVERSAL::AUTOLOAD could cause trouble */
	if (len == autolen && strnEQ(name, autoload, autolen))
	    return Nullgv;
	if (!(gv = gv_fetchmeth(stash, autoload, autolen, FALSE)))
	    return Nullgv;
	cv = GvCV(gv);
	if (!(CvROOT(cv) || CvXSUB(cv)))
	    return Nullgv;
	/* Have an autoload */
	if (level < 0)	/* Cannot do without a stub */
	    gv_fetchmeth(stash, name, len, 0);
	gvp = (GV**)hv_fetch(stash, name, len, (level >= 0));
	if (!gvp)
	    return Nullgv;
	return *gvp;
    }
    return gv;
}

/*
=for apidoc gv_fetchmethod

See L<gv_fetchmethod_autoload>.

=cut
*/

GV *
Perl_gv_fetchmethod(pTHX_ HV *stash, const char *name)
{
    return gv_fetchmethod_autoload(stash, name, TRUE);
}

/*
=for apidoc gv_fetchmethod_autoload

Returns the glob which contains the subroutine to call to invoke the method
on the C<stash>.  In fact in the presence of autoloading this may be the
glob for "AUTOLOAD".  In this case the corresponding variable $AUTOLOAD is
already setup.

The third parameter of C<gv_fetchmethod_autoload> determines whether
AUTOLOAD lookup is performed if the given method is not present: non-zero
means yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD.
Calling C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload>
with a non-zero C<autoload> parameter.

These functions grant C<"SUPER"> token as a prefix of the method name. Note
that if you want to keep the returned glob for a long time, you need to
check for it being "AUTOLOAD", since at the later time the call may load a
different subroutine due to $AUTOLOAD changing its value. Use the glob
created via a side effect to do this.

These functions have the same side-effects and as C<gv_fetchmeth> with
C<level==0>.  C<name> should be writable if contains C<':'> or C<'
''>. The warning against passing the GV returned by C<gv_fetchmeth> to
C<call_sv> apply equally to these functions.

=cut
*/

GV *
Perl_gv_fetchmethod_autoload(pTHX_ HV *stash, const char *name, I32 autoload)
{
    register const char *nend;
    const char *nsplit = 0;
    GV* gv;

    for (nend = name; *nend; nend++) {
	if (*nend == '\'')
	    nsplit = nend;
	else if (*nend == ':' && *(nend + 1) == ':')
	    nsplit = ++nend;
    }
    if (nsplit) {
	const char *origname = name;
	name = nsplit + 1;
	if (*nsplit == ':')
	    --nsplit;
	if ((nsplit - origname) == 5 && strnEQ(origname, "SUPER", 5)) {
	    /* ->SUPER::method should really be looked up in original stash */
	    SV *tmpstr = sv_2mortal(Perl_newSVpvf(aTHX_ "%s::SUPER",
						  CopSTASHPV(PL_curcop)));
	    /* __PACKAGE__::SUPER stash should be autovivified */
	    stash = gv_stashpvn(SvPVX(tmpstr), SvCUR(tmpstr), TRUE);
	    DEBUG_o( Perl_deb(aTHX_ "Treating %s as %s::%s\n",
			 origname, HvNAME(stash), name) );
	}
	else
            /* don't autovifify if ->NoSuchStash::method */
            stash = gv_stashpvn(origname, nsplit - origname, FALSE);
    }

    gv = gv_fetchmeth(stash, name, nend - name, 0);
    if (!gv) {
	if (strEQ(name,"import") || strEQ(name,"unimport"))
	    gv = (GV*)&PL_sv_yes;
	else if (autoload)
	    gv = gv_autoload4(stash, name, nend - name, TRUE);
    }
    else if (autoload) {
	CV* cv = GvCV(gv);
	if (!CvROOT(cv) && !CvXSUB(cv)) {
	    GV* stubgv;
	    GV* autogv;

	    if (CvANON(cv))
		stubgv = gv;
	    else {
		stubgv = CvGV(cv);
		if (GvCV(stubgv) != cv)		/* orphaned import */
		    stubgv = gv;
	    }
	    autogv = gv_autoload4(GvSTASH(stubgv),
				  GvNAME(stubgv), GvNAMELEN(stubgv), TRUE);
	    if (autogv)
		gv = autogv;
	}
    }

    return gv;
}

GV*
Perl_gv_autoload4(pTHX_ HV *stash, const char *name, STRLEN len, I32 method)
{
    char autoload[] = "AUTOLOAD";
    STRLEN autolen = sizeof(autoload)-1;
    GV* gv;
    CV* cv;
    HV* varstash;
    GV* vargv;
    SV* varsv;

    if (!stash)
	return Nullgv;	/* UNIVERSAL::AUTOLOAD could cause trouble */
    if (len == autolen && strnEQ(name, autoload, autolen))
	return Nullgv;
    if (!(gv = gv_fetchmeth(stash, autoload, autolen, FALSE)))
	return Nullgv;
    cv = GvCV(gv);

    if (!(CvROOT(cv) || CvXSUB(cv)))
	return Nullgv;

    /*
     * Inheriting AUTOLOAD for non-methods works ... for now.
     */
    if (ckWARN2(WARN_DEPRECATED, WARN_SYNTAX) && !method &&
	(GvCVGEN(gv) || GvSTASH(gv) != stash))
	Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX),
	  "Use of inherited AUTOLOAD for non-method %s::%.*s() is deprecated",
	     HvNAME(stash), (int)len, name);

#ifndef USE_5005THREADS
    if (CvXSUB(cv)) {
        /* rather than lookup/init $AUTOLOAD here
         * only to have the XSUB do another lookup for $AUTOLOAD
         * and split that value on the last '::',
         * pass along the same data via some unused fields in the CV
         */
        CvSTASH(cv) = stash;
        SvPVX(cv) = (char *)name; /* cast to lose constness warning */
        SvCUR(cv) = len;
        return gv;
    }
#endif

    /*
     * Given &FOO::AUTOLOAD, set $FOO::AUTOLOAD to desired function name.
     * The subroutine's original name may not be "AUTOLOAD", so we don't
     * use that, but for lack of anything better we will use the sub's
     * original package to look up $AUTOLOAD.
     */
    varstash = GvSTASH(CvGV(cv));
    vargv = *(GV**)hv_fetch(varstash, autoload, autolen, TRUE);
    ENTER;

#ifdef USE_5005THREADS
    sv_lock((SV *)varstash);
#endif
    if (!isGV(vargv))
	gv_init(vargv, varstash, autoload, autolen, FALSE);
    LEAVE;
    varsv = GvSV(vargv);
#ifdef USE_5005THREADS
    sv_lock(varsv);
#endif
    sv_setpv(varsv, HvNAME(stash));
    sv_catpvn(varsv, "::", 2);
    sv_catpvn(varsv, name, len);
    SvTAINTED_off(varsv);
    return gv;
}

/* The "gv" parameter should be the glob known to Perl code as *!
 * The scalar must already have been magicalized.
 */
STATIC void
S_require_errno(pTHX_ GV *gv)
{
    HV* stash = gv_stashpvn("Errno",5,FALSE);

    if (!stash || !(gv_fetchmethod(stash, "TIEHASH"))) { 
	dSP;
	PUTBACK;
	ENTER;
	save_scalar(gv); /* keep the value of $! */
        Perl_load_module(aTHX_ PERL_LOADMOD_NOIMPORT,
                         newSVpvn("Errno",5), Nullsv);
	LEAVE;
	SPAGAIN;
	stash = gv_stashpvn("Errno",5,FALSE);
	if (!stash || !(gv_fetchmethod(stash, "TIEHASH")))
	    Perl_croak(aTHX_ "Can't use %%! because Errno.pm is not available");
    }
}

/*
=for apidoc gv_stashpv

Returns a pointer to the stash for a specified package.  C<name> should
be a valid UTF-8 string.  If C<create> is set then the package will be
created if it does not already exist.  If C<create> is not set and the
package does not exist then NULL is returned.

=cut
*/

HV*
Perl_gv_stashpv(pTHX_ const char *name, I32 create)
{
    return gv_stashpvn(name, strlen(name), create);
}

HV*
Perl_gv_stashpvn(pTHX_ const char *name, U32 namelen, I32 create)
{
    char smallbuf[256];
    char *tmpbuf;
    HV *stash;
    GV *tmpgv;

    if (namelen + 3 < sizeof smallbuf)
	tmpbuf = smallbuf;
    else
	New(606, tmpbuf, namelen + 3, char);
    Copy(name,tmpbuf,namelen,char);
    tmpbuf[namelen++] = ':';
    tmpbuf[namelen++] = ':';
    tmpbuf[namelen] = '\0';
    tmpgv = gv_fetchpv(tmpbuf, create, SVt_PVHV);
    if (tmpbuf != smallbuf)
	Safefree(tmpbuf);
    if (!tmpgv)
	return 0;
    if (!GvHV(tmpgv))
	GvHV(tmpgv) = newHV();
    stash = GvHV(tmpgv);
    if (!HvNAME(stash))
	HvNAME(stash) = savepv(name);
    return stash;
}

/*
=for apidoc gv_stashsv

Returns a pointer to the stash for a specified package, which must be a
valid UTF-8 string.  See C<gv_stashpv>.

=cut
*/

HV*
Perl_gv_stashsv(pTHX_ SV *sv, I32 create)
{
    register char *ptr;
    STRLEN len;
    ptr = SvPV(sv,len);
    return gv_stashpvn(ptr, len, create);
}


GV *
Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
{
    register const char *name = nambeg;
    register GV *gv = 0;
    GV**gvp;
    I32 len;
    register const char *namend;
    HV *stash = 0;

    if (*name == '*' && isALPHA(name[1])) /* accidental stringify on a GV? */
	name++;

    for (namend = name; *namend; namend++) {
	if ((*namend == ':' && namend[1] == ':')
	    || (*namend == '\'' && namend[1]))
	{
	    if (!stash)
		stash = PL_defstash;
	    if (!stash || !SvREFCNT(stash)) /* symbol table under destruction */
		return Nullgv;

	    len = namend - name;
	    if (len > 0) {
		char smallbuf[256];
		char *tmpbuf;

		if (len + 3 < sizeof smallbuf)
		    tmpbuf = smallbuf;
		else
		    New(601, tmpbuf, len+3, char);
		Copy(name, tmpbuf, len, char);
		tmpbuf[len++] = ':';
		tmpbuf[len++] = ':';
		tmpbuf[len] = '\0';
		gvp = (GV**)hv_fetch(stash,tmpbuf,len,add);
		gv = gvp ? *gvp : Nullgv;
		if (gv && gv != (GV*)&PL_sv_undef) {
		    if (SvTYPE(gv) != SVt_PVGV)
			gv_init(gv, stash, tmpbuf, len, (add & GV_ADDMULTI));
		    else
			GvMULTI_on(gv);
		}
		if (tmpbuf != smallbuf)
		    Safefree(tmpbuf);
		if (!gv || gv == (GV*)&PL_sv_undef)
		    return Nullgv;

		if (!(stash = GvHV(gv)))
		    stash = GvHV(gv) = newHV();

		if (!HvNAME(stash))
		    HvNAME(stash) = savepvn(nambeg, namend - nambeg);
	    }

	    if (*namend == ':')
		namend++;
	    namend++;
	    name = namend;
	    if (!*name)
		return gv ? gv : (GV*)*hv_fetch(PL_defstash, "main::", 6, TRUE);
	}
    }
    len = namend - name;
    if (!len)
	len = 1;

    /* No stash in name, so see how we can default */

    if (!stash) {
	if (isIDFIRST_lazy(name)) {
	    bool global = FALSE;

	    if (isUPPER(*name)) {
		if (*name == 'S' && (
		    strEQ(name, "SIG") ||
		    strEQ(name, "STDIN") ||
		    strEQ(name, "STDOUT") ||
		    strEQ(name, "STDERR")))
		    global = TRUE;
		else if (*name == 'I' && strEQ(name, "INC"))
		    global = TRUE;
		else if (*name == 'E' && strEQ(name, "ENV"))
		    global = TRUE;
		else if (*name == 'A' && (
		  strEQ(name, "ARGV") ||
		  strEQ(name, "ARGVOUT")))
		    global = TRUE;
	    }
	    else if (*name == '_' && !name[1])
		global = TRUE;

	    if (global)
		stash = PL_defstash;
	    else if ((COP*)PL_curcop == &PL_compiling) {
		stash = PL_curstash;
		if (add && (PL_hints & HINT_STRICT_VARS) &&
		    sv_type != SVt_PVCV &&
		    sv_type != SVt_PVGV &&
		    sv_type != SVt_PVFM &&
		    sv_type != SVt_PVIO &&
		    !(len == 1 && sv_type == SVt_PV && strchr("ab",*name)) )
		{
		    gvp = (GV**)hv_fetch(stash,name,len,0);
		    if (!gvp ||
			*gvp == (GV*)&PL_sv_undef ||
			SvTYPE(*gvp) != SVt_PVGV)
		    {
			stash = 0;
		    }
		    else if ((sv_type == SVt_PV   && !GvIMPORTED_SV(*gvp)) ||
			     (sv_type == SVt_PVAV && !GvIMPORTED_AV(*gvp)) ||
			     (sv_type == SVt_PVHV && !GvIMPORTED_HV(*gvp)) )
		    {
			Perl_warn(aTHX_ "Variable \"%c%s\" is not imported",
			    sv_type == SVt_PVAV ? '@' :
			    sv_type == SVt_PVHV ? '%' : '$',
			    name);
			if (GvCVu(*gvp))
			    Perl_warn(aTHX_ "\t(Did you mean &%s instead?)\n", name);
			stash = 0;
		    }
		}
	    }
	    else
		stash = CopSTASH(PL_curcop);
	}
	else
	    stash = PL_defstash;
    }

    /* By this point we should have a stash and a name */

    if (!stash) {
	if (add) {
	    qerror(Perl_mess(aTHX_
		 "Global symbol \"%s%s\" requires explicit package name",
		 (sv_type == SVt_PV ? "$"
		  : sv_type == SVt_PVAV ? "@"
		  : sv_type == SVt_PVHV ? "%"
		  : ""), name));
	    stash = PL_nullstash;
	}
	else
	    return Nullgv;
    }

    if (!SvREFCNT(stash))	/* symbol table under destruction */
	return Nullgv;

    gvp = (GV**)hv_fetch(stash,name,len,add);
    if (!gvp || *gvp == (GV*)&PL_sv_undef)
	return Nullgv;
    gv = *gvp;
    if (SvTYPE(gv) == SVt_PVGV) {
	if (add) {
	    GvMULTI_on(gv);
	    gv_init_sv(gv, sv_type);
	    if (*name=='!' && sv_type == SVt_PVHV && len==1)
		require_errno(gv);
	}
	return gv;
    } else if (add & GV_NOINIT) {
	return gv;
    }

    /* Adding a new symbol */

    if (add & GV_ADDWARN && ckWARN_d(WARN_INTERNAL))
	Perl_warner(aTHX_ packWARN(WARN_INTERNAL), "Had to create %s unexpectedly", nambeg);
    gv_init(gv, stash, name, len, add & GV_ADDMULTI);
    gv_init_sv(gv, sv_type);

    if (isALPHA(name[0]) && ! (isLEXWARN_on ? ckWARN(WARN_ONCE) 
			                    : (PL_dowarn & G_WARN_ON ) ) )
        GvMULTI_on(gv) ;

    /* set up magic where warranted */
    switch (*name) {
    case 'A':
	if (strEQ(name, "ARGV")) {
	    IoFLAGS(GvIOn(gv)) |= IOf_ARGV|IOf_START;
	}
	break;
    case 'E':
	if (strnEQ(name, "EXPORT", 6))
	    GvMULTI_on(gv);
	break;
    case 'I':
	if (strEQ(name, "ISA")) {
	    AV* av = GvAVn(gv);
	    GvMULTI_on(gv);
	    sv_magic((SV*)av, (SV*)gv, PERL_MAGIC_isa, Nullch, 0);
	    /* NOTE: No support for tied ISA */
	    if ((add & GV_ADDMULTI) && strEQ(nambeg,"AnyDBM_File::ISA")
		&& AvFILLp(av) == -1)
	    {
		char *pname;
		av_push(av, newSVpvn(pname = "NDBM_File",9));
		gv_stashpvn(pname, 9, TRUE);
		av_push(av, newSVpvn(pname = "DB_File",7));
		gv_stashpvn(pname, 7, TRUE);
		av_push(av, newSVpvn(pname = "GDBM_File",9));
		gv_stashpvn(pname, 9, TRUE);
		av_push(av, newSVpvn(pname = "SDBM_File",9));
		gv_stashpvn(pname, 9, TRUE);
		av_push(av, newSVpvn(pname = "ODBM_File",9));
		gv_stashpvn(pname, 9, TRUE);
	    }
	}
	break;
    case 'O':
        if (strEQ(name, "OVERLOAD")) {
            HV* hv = GvHVn(gv);
            GvMULTI_on(gv);
            hv_magic(hv, Nullgv, PERL_MAGIC_overload);
        }
        break;
    case 'S':
	if (strEQ(name, "SIG")) {
	    HV *hv;
	    I32 i;
	    if (!PL_psig_ptr) {
		Newz(73, PL_psig_ptr,  SIG_SIZE, SV*);
		Newz(73, PL_psig_name, SIG_SIZE, SV*);
		Newz(73, PL_psig_pend, SIG_SIZE, int);
	    }
	    GvMULTI_on(gv);
	    hv = GvHVn(gv);
	    hv_magic(hv, Nullgv, PERL_MAGIC_sig);
	    for (i = 1; i < SIG_SIZE; i++) {
	    	SV ** init;
	    	init = hv_fetch(hv, PL_sig_name[i], strlen(PL_sig_name[i]), 1);
	    	if (init)
		    sv_setsv(*init, &PL_sv_undef);
	    	PL_psig_ptr[i] = 0;
	    	PL_psig_name[i] = 0;
	    	PL_psig_pend[i] = 0;
	    }
	}
	break;
    case 'V':
	if (strEQ(name, "VERSION"))
	    GvMULTI_on(gv);
	break;

    case '&':
    case '`':
    case '\'':
       if (
           len > 1 ||
           sv_type == SVt_PVAV ||
           sv_type == SVt_PVHV ||
           sv_type == SVt_PVCV ||
           sv_type == SVt_PVFM ||
           sv_type == SVt_PVIO
       ) { break; }
	PL_sawampersand = TRUE;
	goto ro_magicalize;

    case ':':
	if (len > 1)
	    break;
	sv_setpv(GvSV(gv),PL_chopset);
	goto magicalize;

    case '?':
	if (len > 1)
	    break;
#ifdef COMPLEX_STATUS
	(void)SvUPGRADE(GvSV(gv), SVt_PVLV);
#endif
	goto magicalize;

    case '!':
	if (len > 1)
	    break;

	/* If %! has been used, automatically load Errno.pm.
	   The require will itself set errno, so in order to
	   preserve its value we have to set up the magic
	   now (rather than going to magicalize)
	*/

	sv_magic(GvSV(gv), (SV*)gv, PERL_MAGIC_sv, name, len);

	if (sv_type == SVt_PVHV)
	    require_errno(gv);

	break;
    case '-':
	if (len > 1)
	    break;
	else {
            AV* av = GvAVn(gv);
            sv_magic((SV*)av, Nullsv, PERL_MAGIC_regdata, Nullch, 0);
	    SvREADONLY_on(av);
        }
	goto magicalize;
    case '#':
    case '*':
	if (ckWARN2(WARN_DEPRECATED, WARN_SYNTAX) && len == 1 && sv_type == SVt_PV)
	    Perl_warner(aTHX_ packWARN2(WARN_DEPRECATED, WARN_SYNTAX), "Use of $%s is deprecated", name);
	/* FALL THROUGH */
    case '[':
    case '^':
    case '~':
    case '=':
    case '%':
    case '.':
    case '(':
    case ')':
    case '<':
    case '>':
    case ',':
    case '\\':
    case '/':
    case '\001':	/* $^A */
    case '\003':	/* $^C */
    case '\004':	/* $^D */
    case '\006':	/* $^F */
    case '\010':	/* $^H */
    case '\011':	/* $^I, NOT \t in EBCDIC */
    case '\016':        /* $^N */
    case '\020':	/* $^P */
	if (len > 1)
	    break;
	goto magicalize;
    case '|':
	if (len > 1)
	    break;
	sv_setiv(GvSV(gv), (IV)(IoFLAGS(GvIOp(PL_defoutgv)) & IOf_FLUSH) != 0);
	goto magicalize;
    case '\005':	/* $^E && $^ENCODING */
	if (len > 1 && strNE(name, "\005NCODING"))
	    break;
	goto magicalize;

    case '\017':	/* $^O & $^OPEN */
	if (len > 1 && strNE(name, "\017PEN"))
	    break;
	goto magicalize;
    case '\023':	/* $^S */
	if (len > 1)
	    break;
	goto ro_magicalize;
    case '\024':	/* $^T, ${^TAINT} */
        if (len == 1)
            goto magicalize;
        else if (strEQ(name, "\024AINT"))
            goto ro_magicalize;
        else
            break;
    case '\027':	/* $^W & $^WARNING_BITS */
	if (len > 1 && strNE(name, "\027ARNING_BITS")
	    && strNE(name, "\027IDE_SYSTEM_CALLS"))
	    break;
	goto magicalize;

    case '+':
	if (len > 1)
	    break;
	else {
            AV* av = GvAVn(gv);
            sv_magic((SV*)av, (SV*)av, PERL_MAGIC_regdata, Nullch, 0);
	    SvREADONLY_on(av);
        }
	/* FALL THROUGH */
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
	/* ensures variable is only digits */
	/* ${"1foo"} fails this test (and is thus writeable) */
	/* added by japhy, but borrowed from is_gv_magical */

	if (len > 1) {
	    const char *end = name + len;
	    while (--end > name) {
		if (!isDIGIT(*end)) return gv;
	    }
	}

      ro_magicalize:
	SvREADONLY_on(GvSV(gv));
      magicalize:
	sv_magic(GvSV(gv), (SV*)gv, PERL_MAGIC_sv, name, len);
	break;

    case '\014':	/* $^L */
	if (len > 1)
	    break;
	sv_setpv(GvSV(gv),"\f");
	PL_formfeed = GvSV(gv);
	break;
    case ';':
	if (len > 1)
	    break;
	sv_setpv(GvSV(gv),"\034");
	break;
    case ']':
	if (len == 1) {
	    SV *sv = GvSV(gv);
	    (void)SvUPGRADE(sv, SVt_PVNV);
	    Perl_sv_setpvf(aTHX_ sv,
#if defined(PERL_SUBVERSION) && (PERL_SUBVERSION > 0)
			    "%8.6"
#else
			    "%5.3"
#endif
			    NVff,
			    SvNVX(PL_patchlevel));
	    SvNVX(sv) = SvNVX(PL_patchlevel);
	    SvNOK_on(sv);
	    SvREADONLY_on(sv);
	}
	break;
    case '\026':	/* $^V */
	if (len == 1) {
	    SV *sv = GvSV(gv);
	    GvSV(gv) = SvREFCNT_inc(PL_patchlevel);
	    SvREFCNT_dec(sv);
	}
	break;
    }
    return gv;
}

void
Perl_gv_fullname4(pTHX_ SV *sv, GV *gv, const char *prefix, bool keepmain)
{
    HV *hv = GvSTASH(gv);
    if (!hv) {
	(void)SvOK_off(sv);
	return;
    }
    sv_setpv(sv, prefix ? prefix : "");
    if (keepmain || strNE(HvNAME(hv), "main")) {
	sv_catpv(sv,HvNAME(hv));
	sv_catpvn(sv,"::", 2);
    }
    sv_catpvn(sv,GvNAME(gv),GvNAMELEN(gv));
}

void
Perl_gv_fullname3(pTHX_ SV *sv, GV *gv, const char *prefix)
{
    HV *hv = GvSTASH(gv);
    if (!hv) {
	(void)SvOK_off(sv);
	return;
    }
    sv_setpv(sv, prefix ? prefix : "");
    sv_catpv(sv,HvNAME(hv));
    sv_catpvn(sv,"::", 2);
    sv_catpvn(sv,GvNAME(gv),GvNAMELEN(gv));
}

void
Perl_gv_efullname4(pTHX_ SV *sv, GV *gv, const char *prefix, bool keepmain)
{
    GV *egv = GvEGV(gv);
    if (!egv)
	egv = gv;
    gv_fullname4(sv, egv, prefix, keepmain);
}

void
Perl_gv_efullname3(pTHX_ SV *sv, GV *gv, const char *prefix)
{
    GV *egv = GvEGV(gv);
    if (!egv)
	egv = gv;
    gv_fullname3(sv, egv, prefix);
}

/* XXX compatibility with versions <= 5.003. */
void
Perl_gv_fullname(pTHX_ SV *sv, GV *gv)
{
    gv_fullname3(sv, gv, sv == (SV*)gv ? "*" : "");
}

/* XXX compatibility with versions <= 5.003. */
void
Perl_gv_efullname(pTHX_ SV *sv, GV *gv)
{
    gv_efullname3(sv, gv, sv == (SV*)gv ? "*" : "");
}

IO *
Perl_newIO(pTHX)
{
    IO *io;
    GV *iogv;

    io = (IO*)NEWSV(0,0);
    sv_upgrade((SV *)io,SVt_PVIO);
    SvREFCNT(io) = 1;
    SvOBJECT_on(io);
    iogv = gv_fetchpv("FileHandle::", FALSE, SVt_PVHV);
    /* unless exists($main::{FileHandle}) and defined(%main::FileHandle::) */
    if (!(iogv && GvHV(iogv) && HvARRAY(GvHV(iogv))))
      iogv = gv_fetchpv("IO::Handle::", TRUE, SVt_PVHV);
    SvSTASH(io) = (HV*)SvREFCNT_inc(GvHV(iogv));
    return io;
}

void
Perl_gv_check(pTHX_ HV *stash)
{
    register HE *entry;
    register I32 i;
    register GV *gv;
    HV *hv;

    if (!HvARRAY(stash))
	return;
    for (i = 0; i <= (I32) HvMAX(stash); i++) {
	for (entry = HvARRAY(stash)[i]; entry; entry = HeNEXT(entry)) {
	    if (HeKEY(entry)[HeKLEN(entry)-1] == ':' &&
		(gv = (GV*)HeVAL(entry)) && (hv = GvHV(gv)))
	    {
		if (hv != PL_defstash && hv != stash)
		     gv_check(hv);              /* nested package */
	    }
	    else if (isALPHA(*HeKEY(entry))) {
		char *file;
		gv = (GV*)HeVAL(entry);
		if (SvTYPE(gv) != SVt_PVGV || GvMULTI(gv))
		    continue;
		file = GvFILE(gv);
		/* performance hack: if filename is absolute and it's a standard
		 * module, don't bother warning */
		if (file
		    && PERL_FILE_IS_ABSOLUTE(file)
#ifdef MACOS_TRADITIONAL
		    && (instr(file, ":lib:")
#else
		    && (instr(file, "/lib/")
#endif
		    || instr(file, ".pm")))
		{
		    continue;
		}
		CopLINE_set(PL_curcop, GvLINE(gv));
#ifdef USE_ITHREADS
		CopFILE(PL_curcop) = file;	/* set for warning */
#else
		CopFILEGV(PL_curcop) = gv_fetchfile(file);
#endif
		Perl_warner(aTHX_ packWARN(WARN_ONCE),
			"Name \"%s::%s\" used only once: possible typo",
			HvNAME(stash), GvNAME(gv));
	    }
	}
    }
}

GV *
Perl_newGVgen(pTHX_ char *pack)
{
    return gv_fetchpv(Perl_form(aTHX_ "%s::_GEN_%ld", pack, (long)PL_gensym++),
		      TRUE, SVt_PVGV);
}

/* hopefully this is only called on local symbol table entries */

GP*
Perl_gp_ref(pTHX_ GP *gp)
{
    if (!gp)
	return (GP*)NULL;
    gp->gp_refcnt++;
    if (gp->gp_cv) {
	if (gp->gp_cvgen) {
	    /* multi-named GPs cannot be used for method cache */
	    SvREFCNT_dec(gp->gp_cv);
	    gp->gp_cv = Nullcv;
	    gp->gp_cvgen = 0;
	}
	else {
	    /* Adding a new name to a subroutine invalidates method cache */
	    PL_sub_generation++;
	}
    }
    return gp;
}

void
Perl_gp_free(pTHX_ GV *gv)
{
    GP* gp;

    if (!gv || !(gp = GvGP(gv)))
	return;
    if (gp->gp_refcnt == 0) {
	if (ckWARN_d(WARN_INTERNAL))
	    Perl_warner(aTHX_ packWARN(WARN_INTERNAL),
			"Attempt to free unreferenced glob pointers");
        return;
    }
    if (gp->gp_cv) {
	/* Deleting the name of a subroutine invalidates method cache */
	PL_sub_generation++;
    }
    if (--gp->gp_refcnt > 0) {
	if (gp->gp_egv == gv)
	    gp->gp_egv = 0;
        return;
    }

    SvREFCNT_dec(gp->gp_sv);
    SvREFCNT_dec(gp->gp_av);
    SvREFCNT_dec(gp->gp_hv);
    SvREFCNT_dec(gp->gp_io);
    SvREFCNT_dec(gp->gp_cv);
    SvREFCNT_dec(gp->gp_form);

    Safefree(gp);
    GvGP(gv) = 0;
}

#if defined(CRIPPLED_CC) && (defined(iAPX286) || defined(M_I286) || defined(I80286))
#define MICROPORT
#endif

#ifdef	MICROPORT	/* Microport 2.4 hack */
AV *GvAVn(gv)
register GV *gv;
{
    if (GvGP(gv)->gp_av)
	return GvGP(gv)->gp_av;
    else
	return GvGP(gv_AVadd(gv))->gp_av;
}

HV *GvHVn(gv)
register GV *gv;
{
    if (GvGP(gv)->gp_hv)
	return GvGP(gv)->gp_hv;
    else
	return GvGP(gv_HVadd(gv))->gp_hv;
}
#endif			/* Microport 2.4 hack */

int
Perl_magic_freeovrld(pTHX_ SV *sv, MAGIC *mg)
{
    AMT *amtp = (AMT*)mg->mg_ptr;
    if (amtp && AMT_AMAGIC(amtp)) {
	int i;
	for (i = 1; i < NofAMmeth; i++) {
	    CV *cv = amtp->table[i];
	    if (cv != Nullcv) {
		SvREFCNT_dec((SV *) cv);
		amtp->table[i] = Nullcv;
	    }
	}
    }
 return 0;
}

/* Updates and caches the CV's */

bool
Perl_Gv_AMupdate(pTHX_ HV *stash)
{
  GV* gv;
  CV* cv;
  MAGIC* mg=mg_find((SV*)stash, PERL_MAGIC_overload_table);
  AMT *amtp = (mg) ? (AMT*)mg->mg_ptr: (AMT *) NULL;
  AMT amt;

  if (mg && amtp->was_ok_am == PL_amagic_generation
      && amtp->was_ok_sub == PL_sub_generation)
      return AMT_OVERLOADED(amtp);
  sv_unmagic((SV*)stash, PERL_MAGIC_overload_table);

  DEBUG_o( Perl_deb(aTHX_ "Recalcing overload magic in package %s\n",HvNAME(stash)) );

  Zero(&amt,1,AMT);
  amt.was_ok_am = PL_amagic_generation;
  amt.was_ok_sub = PL_sub_generation;
  amt.fallback = AMGfallNO;
  amt.flags = 0;

  {
    int filled = 0, have_ovl = 0;
    int i, lim = 1;
    SV* sv = NULL;

    /* Work with "fallback" key, which we assume to be first in PL_AMG_names */

    /* Try to find via inheritance. */
    gv = gv_fetchmeth(stash, PL_AMG_names[0], 2, -1);
    if (gv)
	sv = GvSV(gv);

    if (!gv)
	lim = DESTROY_amg;		/* Skip overloading entries. */
    else if (SvTRUE(sv))
	amt.fallback=AMGfallYES;
    else if (SvOK(sv))
	amt.fallback=AMGfallNEVER;

    for (i = 1; i < lim; i++)
	amt.table[i] = Nullcv;
    for (; i < NofAMmeth; i++) {
	char *cooky = (char*)PL_AMG_names[i];
	/* Human-readable form, for debugging: */
	char *cp = (i >= DESTROY_amg ? cooky : AMG_id2name(i));
	STRLEN l = strlen(cooky);

	DEBUG_o( Perl_deb(aTHX_ "Checking overloading of `%s' in package `%.256s'\n",
		     cp, HvNAME(stash)) );
	/* don't fill the cache while looking up!
	   Creation of inheritance stubs in intermediate packages may
	   conflict with the logic of runtime method substitution.
	   Indeed, for inheritance A -> B -> C, if C overloads "+0",
	   then we could have created stubs for "(+0" in A and C too.
	   But if B overloads "bool", we may want to use it for
	   numifying instead of C's "+0". */
	if (i >= DESTROY_amg)
	    gv = Perl_gv_fetchmeth_autoload(aTHX_ stash, cooky, l, 0);
	else				/* Autoload taken care of below */
	    gv = Perl_gv_fetchmeth(aTHX_ stash, cooky, l, -1);
        cv = 0;
        if (gv && (cv = GvCV(gv))) {
	    if (GvNAMELEN(CvGV(cv)) == 3 && strEQ(GvNAME(CvGV(cv)), "nil")
		&& strEQ(HvNAME(GvSTASH(CvGV(cv))), "overload")) {
		/* This is a hack to support autoloading..., while
		   knowing *which* methods were declared as overloaded. */
		/* GvSV contains the name of the method. */
		GV *ngv = Nullgv;
		
		DEBUG_o( Perl_deb(aTHX_ "Resolving method `%.256s' for overloaded `%s' in package `%.256s'\n",
			     SvPV_nolen(GvSV(gv)), cp, HvNAME(stash)) );
		if (!SvPOK(GvSV(gv))
		    || !(ngv = gv_fetchmethod_autoload(stash, SvPVX(GvSV(gv)),
						       FALSE)))
		{
		    /* Can be an import stub (created by `can'). */
		    if (GvCVGEN(gv)) {
			Perl_croak(aTHX_ "Stub found while resolving method `%.256s' overloading `%s' in package `%.256s'",
			      (SvPOK(GvSV(gv)) ?  SvPVX(GvSV(gv)) : "???" ),
			      cp, HvNAME(stash));
		    } else
			Perl_croak(aTHX_ "Can't resolve method `%.256s' overloading `%s' in package `%.256s'",
			      (SvPOK(GvSV(gv)) ?  SvPVX(GvSV(gv)) : "???" ),
			      cp, HvNAME(stash));
		}
		cv = GvCV(gv = ngv);
	    }
	    DEBUG_o( Perl_deb(aTHX_ "Overloading `%s' in package `%.256s' via `%.256s::%.256s' \n",
			 cp, HvNAME(stash), HvNAME(GvSTASH(CvGV(cv))),
			 GvNAME(CvGV(cv))) );
	    filled = 1;
	    if (i < DESTROY_amg)
		have_ovl = 1;
	} else if (gv) {		/* Autoloaded... */
	    cv = (CV*)gv;
	    filled = 1;
	}
	amt.table[i]=(CV*)SvREFCNT_inc(cv);
    }
    if (filled) {
      AMT_AMAGIC_on(&amt);
      if (have_ovl)
	  AMT_OVERLOADED_on(&amt);
      sv_magic((SV*)stash, 0, PERL_MAGIC_overload_table,
						(char*)&amt, sizeof(AMT));
      return have_ovl;
    }
  }
  /* Here we have no table: */
  /* no_table: */
  AMT_AMAGIC_off(&amt);
  sv_magic((SV*)stash, 0, PERL_MAGIC_overload_table,
						(char*)&amt, sizeof(AMTS));
  return FALSE;
}


CV*
Perl_gv_handler(pTHX_ HV *stash, I32 id)
{
    MAGIC *mg;
    AMT *amtp;
    CV *ret;

    if (!stash)
        return Nullcv;
    mg = mg_find((SV*)stash, PERL_MAGIC_overload_table);
    if (!mg) {
      do_update:
	Gv_AMupdate(stash);
	mg = mg_find((SV*)stash, PERL_MAGIC_overload_table);
    }
    amtp = (AMT*)mg->mg_ptr;
    if ( amtp->was_ok_am != PL_amagic_generation
	 || amtp->was_ok_sub != PL_sub_generation )
	goto do_update;
    if (AMT_AMAGIC(amtp)) {
	ret = amtp->table[id];
	if (ret && isGV(ret)) {		/* Autoloading stab */
	    /* Passing it through may have resulted in a warning
	       "Inherited AUTOLOAD for a non-method deprecated", since
	       our caller is going through a function call, not a method call.
	       So return the CV for AUTOLOAD, setting $AUTOLOAD. */
	    GV *gv = gv_fetchmethod(stash, (char*)PL_AMG_names[id]);

	    if (gv && GvCV(gv))
		return GvCV(gv);
	}
	return ret;
    }
    
    return Nullcv;
}


SV*
Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
{
  MAGIC *mg;
  CV *cv=NULL;
  CV **cvp=NULL, **ocvp=NULL;
  AMT *amtp=NULL, *oamtp=NULL;
  int off=0, off1, lr=0, assign=AMGf_assign & flags, notfound=0;
  int postpr = 0, force_cpy = 0, assignshift = assign ? 1 : 0;
#ifdef DEBUGGING
  int fl=0;
#endif
  HV* stash=NULL;
  if (!(AMGf_noleft & flags) && SvAMAGIC(left)
      && (stash = SvSTASH(SvRV(left)))
      && (mg = mg_find((SV*)stash, PERL_MAGIC_overload_table))
      && (ocvp = cvp = (AMT_AMAGIC((AMT*)mg->mg_ptr)
			? (oamtp = amtp = (AMT*)mg->mg_ptr)->table
			: (CV **) NULL))
      && ((cv = cvp[off=method+assignshift])
	  || (assign && amtp->fallback > AMGfallNEVER && /* fallback to
						          * usual method */
		  (
#ifdef DEBUGGING
		   fl = 1,
#endif 
		   cv = cvp[off=method])))) {
    lr = -1;			/* Call method for left argument */
  } else {
    if (cvp && amtp->fallback > AMGfallNEVER && flags & AMGf_unary) {
      int logic;

      /* look for substituted methods */
      /* In all the covered cases we should be called with assign==0. */
	 switch (method) {
	 case inc_amg:
	   force_cpy = 1;
	   if ((cv = cvp[off=add_ass_amg])
	       || ((cv = cvp[off = add_amg]) && (force_cpy = 0, postpr = 1))) {
	     right = &PL_sv_yes; lr = -1; assign = 1;
	   }
	   break;
	 case dec_amg:
	   force_cpy = 1;
	   if ((cv = cvp[off = subtr_ass_amg])
	       || ((cv = cvp[off = subtr_amg]) && (force_cpy = 0, postpr=1))) {
	     right = &PL_sv_yes; lr = -1; assign = 1;
	   }
	   break;
	 case bool__amg:
	   (void)((cv = cvp[off=numer_amg]) || (cv = cvp[off=string_amg]));
	   break;
	 case numer_amg:
	   (void)((cv = cvp[off=string_amg]) || (cv = cvp[off=bool__amg]));
	   break;
	 case string_amg:
	   (void)((cv = cvp[off=numer_amg]) || (cv = cvp[off=bool__amg]));
	   break;
 case not_amg:
   (void)((cv = cvp[off=bool__amg])
	  || (cv = cvp[off=numer_amg])
	  || (cv = cvp[off=string_amg]));
   postpr = 1;
   break;
	 case copy_amg:
	   {
	     /*
		  * SV* ref causes confusion with the interpreter variable of
		  * the same name
		  */
	     SV* tmpRef=SvRV(left);
	     if (!SvROK(tmpRef) && SvTYPE(tmpRef) <= SVt_PVMG) {
		/*
		 * Just to be extra cautious.  Maybe in some
		 * additional cases sv_setsv is safe, too.
		 */
		SV* newref = newSVsv(tmpRef);
		SvOBJECT_on(newref);
		SvSTASH(newref) = (HV*)SvREFCNT_inc(SvSTASH(tmpRef));
		return newref;
	     }
	   }
	   break;
	 case abs_amg:
	   if ((cvp[off1=lt_amg] || cvp[off1=ncmp_amg])
	       && ((cv = cvp[off=neg_amg]) || (cv = cvp[off=subtr_amg]))) {
	     SV* nullsv=sv_2mortal(newSViv(0));
	     if (off1==lt_amg) {
	       SV* lessp = amagic_call(left,nullsv,
				       lt_amg,AMGf_noright);
	       logic = SvTRUE(lessp);
	     } else {
	       SV* lessp = amagic_call(left,nullsv,
				       ncmp_amg,AMGf_noright);
	       logic = (SvNV(lessp) < 0);
	     }
	     if (logic) {
	       if (off==subtr_amg) {
		 right = left;
		 left = nullsv;
		 lr = 1;
	       }
	     } else {
	       return left;
	     }
	   }
	   break;
	 case neg_amg:
	   if ((cv = cvp[off=subtr_amg])) {
	     right = left;
	     left = sv_2mortal(newSViv(0));
	     lr = 1;
	   }
	   break;
	 case int_amg:
	 case iter_amg:			/* XXXX Eventually should do to_gv. */
	     /* FAIL safe */
	     return NULL;	/* Delegate operation to standard mechanisms. */
	     break;
	 case to_sv_amg:
	 case to_av_amg:
	 case to_hv_amg:
	 case to_gv_amg:
	 case to_cv_amg:
	     /* FAIL safe */
	     return left;	/* Delegate operation to standard mechanisms. */
	     break;
	 default:
	   goto not_found;
	 }
	 if (!cv) goto not_found;
    } else if (!(AMGf_noright & flags) && SvAMAGIC(right)
	       && (stash = SvSTASH(SvRV(right)))
	       && (mg = mg_find((SV*)stash, PERL_MAGIC_overload_table))
	       && (cvp = (AMT_AMAGIC((AMT*)mg->mg_ptr)
			  ? (amtp = (AMT*)mg->mg_ptr)->table
			  : (CV **) NULL))
	       && (cv = cvp[off=method])) { /* Method for right
					     * argument found */
      lr=1;
    } else if (((ocvp && oamtp->fallback > AMGfallNEVER
		 && (cvp=ocvp) && (lr = -1))
		|| (cvp && amtp->fallback > AMGfallNEVER && (lr=1)))
	       && !(flags & AMGf_unary)) {
				/* We look for substitution for
				 * comparison operations and
				 * concatenation */
      if (method==concat_amg || method==concat_ass_amg
	  || method==repeat_amg || method==repeat_ass_amg) {
	return NULL;		/* Delegate operation to string conversion */
      }
      off = -1;
      switch (method) {
	 case lt_amg:
	 case le_amg:
	 case gt_amg:
	 case ge_amg:
	 case eq_amg:
	 case ne_amg:
	   postpr = 1; off=ncmp_amg; break;
	 case slt_amg:
	 case sle_amg:
	 case sgt_amg:
	 case sge_amg:
	 case seq_amg:
	 case sne_amg:
	   postpr = 1; off=scmp_amg; break;
	 }
      if (off != -1) cv = cvp[off];
      if (!cv) {
	goto not_found;
      }
    } else {
    not_found:			/* No method found, either report or croak */
      switch (method) {
	 case to_sv_amg:
	 case to_av_amg:
	 case to_hv_amg:
	 case to_gv_amg:
	 case to_cv_amg:
	     /* FAIL safe */
	     return left;	/* Delegate operation to standard mechanisms. */
	     break;
      }
      if (ocvp && (cv=ocvp[nomethod_amg])) { /* Call report method */
	notfound = 1; lr = -1;
      } else if (cvp && (cv=cvp[nomethod_amg])) {
	notfound = 1; lr = 1;
      } else {
	SV *msg;
	if (off==-1) off=method;
	msg = sv_2mortal(Perl_newSVpvf(aTHX_
		      "Operation `%s': no method found,%sargument %s%s%s%s",
		      AMG_id2name(method + assignshift),
		      (flags & AMGf_unary ? " " : "\n\tleft "),
		      SvAMAGIC(left)?
		        "in overloaded package ":
		        "has no overloaded magic",
		      SvAMAGIC(left)?
		        HvNAME(SvSTASH(SvRV(left))):
		        "",
		      SvAMAGIC(right)?
		        ",\n\tright argument in overloaded package ":
		        (flags & AMGf_unary
			 ? ""
			 : ",\n\tright argument has no overloaded magic"),
		      SvAMAGIC(right)?
		        HvNAME(SvSTASH(SvRV(right))):
		        ""));
	if (amtp && amtp->fallback >= AMGfallYES) {
	  DEBUG_o( Perl_deb(aTHX_ "%s", SvPVX(msg)) );
	} else {
	  Perl_croak(aTHX_ "%"SVf, msg);
	}
	return NULL;
      }
      force_cpy = force_cpy || assign;
    }
  }
#ifdef DEBUGGING
  if (!notfound) {
    DEBUG_o(Perl_deb(aTHX_
		     "Overloaded operator `%s'%s%s%s:\n\tmethod%s found%s in package %s%s\n",
		     AMG_id2name(off),
		     method+assignshift==off? "" :
		     " (initially `",
		     method+assignshift==off? "" :
		     AMG_id2name(method+assignshift),
		     method+assignshift==off? "" : "')",
		     flags & AMGf_unary? "" :
		     lr==1 ? " for right argument": " for left argument",
		     flags & AMGf_unary? " for argument" : "",
		     stash ? HvNAME(stash) : "null",
		     fl? ",\n\tassignment variant used": "") );
  }
#endif
    /* Since we use shallow copy during assignment, we need
     * to dublicate the contents, probably calling user-supplied
     * version of copy operator
     */
    /* We need to copy in following cases:
     * a) Assignment form was called.
     * 		assignshift==1,  assign==T, method + 1 == off
     * b) Increment or decrement, called directly.
     * 		assignshift==0,  assign==0, method + 0 == off
     * c) Increment or decrement, translated to assignment add/subtr.
     * 		assignshift==0,  assign==T,
     *		force_cpy == T
     * d) Increment or decrement, translated to nomethod.
     * 		assignshift==0,  assign==0,
     *		force_cpy == T
     * e) Assignment form translated to nomethod.
     * 		assignshift==1,  assign==T, method + 1 != off
     *		force_cpy == T
     */
    /*	off is method, method+assignshift, or a result of opcode substitution.
     *	In the latter case assignshift==0, so only notfound case is important.
     */
  if (( (method + assignshift == off)
	&& (assign || (method == inc_amg) || (method == dec_amg)))
      || force_cpy)
    RvDEEPCP(left);
  {
    dSP;
    BINOP myop;
    SV* res;
    bool oldcatch = CATCH_GET;

    CATCH_SET(TRUE);
    Zero(&myop, 1, BINOP);
    myop.op_last = (OP *) &myop;
    myop.op_next = Nullop;
    myop.op_flags = OPf_WANT_SCALAR | OPf_STACKED;

    PUSHSTACKi(PERLSI_OVERLOAD);
    ENTER;
    SAVEOP();
    PL_op = (OP *) &myop;
    if (PERLDB_SUB && PL_curstash != PL_debstash)
	PL_op->op_private |= OPpENTERSUB_DB;
    PUTBACK;
    pp_pushmark();

    EXTEND(SP, notfound + 5);
    PUSHs(lr>0? right: left);
    PUSHs(lr>0? left: right);
    PUSHs( lr > 0 ? &PL_sv_yes : ( assign ? &PL_sv_undef : &PL_sv_no ));
    if (notfound) {
      PUSHs( sv_2mortal(newSVpv(AMG_id2name(method + assignshift),0)));
    }
    PUSHs((SV*)cv);
    PUTBACK;

    if ((PL_op = Perl_pp_entersub(aTHX)))
      CALLRUNOPS(aTHX);
    LEAVE;
    SPAGAIN;

    res=POPs;
    PUTBACK;
    POPSTACK;
    CATCH_SET(oldcatch);

    if (postpr) {
      int ans=0;
      switch (method) {
      case le_amg:
      case sle_amg:
	ans=SvIV(res)<=0; break;
      case lt_amg:
      case slt_amg:
	ans=SvIV(res)<0; break;
      case ge_amg:
      case sge_amg:
	ans=SvIV(res)>=0; break;
      case gt_amg:
      case sgt_amg:
	ans=SvIV(res)>0; break;
      case eq_amg:
      case seq_amg:
	ans=SvIV(res)==0; break;
      case ne_amg:
      case sne_amg:
	ans=SvIV(res)!=0; break;
      case inc_amg:
      case dec_amg:
	SvSetSV(left,res); return left;
      case not_amg:
	ans=!SvTRUE(res); break;
      }
      return boolSV(ans);
    } else if (method==copy_amg) {
      if (!SvROK(res)) {
	Perl_croak(aTHX_ "Copy method did not return a reference");
      }
      return SvREFCNT_inc(SvRV(res));
    } else {
      return res;
    }
  }
}

/*
=for apidoc is_gv_magical

Returns C<TRUE> if given the name of a magical GV.

Currently only useful internally when determining if a GV should be
created even in rvalue contexts.

C<flags> is not used at present but available for future extension to
allow selecting particular classes of magical variable.

=cut
*/
bool
Perl_is_gv_magical(pTHX_ char *name, STRLEN len, U32 flags)
{
    if (!len)
	return FALSE;

    switch (*name) {
    case 'I':
	if (len == 3 && strEQ(name, "ISA"))
	    goto yes;
	break;
    case 'O':
	if (len == 8 && strEQ(name, "OVERLOAD"))
	    goto yes;
	break;
    case 'S':
	if (len == 3 && strEQ(name, "SIG"))
	    goto yes;
	break;
    case '\017':   /* $^O & $^OPEN */
	if (len == 1
	    || (len == 4 && strEQ(name, "\017PEN")))
	{
	    goto yes;
	}
	break;
    case '\027':   /* $^W & $^WARNING_BITS */
	if (len == 1
	    || (len == 12 && strEQ(name, "\027ARNING_BITS"))
	    || (len == 17 && strEQ(name, "\027IDE_SYSTEM_CALLS")))
	{
	    goto yes;
	}
	break;

    case '&':
    case '`':
    case '\'':
    case ':':
    case '?':
    case '!':
    case '-':
    case '#':
    case '*':
    case '[':
    case '^':
    case '~':
    case '=':
    case '%':
    case '.':
    case '(':
    case ')':
    case '<':
    case '>':
    case ',':
    case '\\':
    case '/':
    case '|':
    case '+':
    case ';':
    case ']':
    case '\001':   /* $^A */
    case '\003':   /* $^C */
    case '\004':   /* $^D */
    case '\005':   /* $^E */
    case '\006':   /* $^F */
    case '\010':   /* $^H */
    case '\011':   /* $^I, NOT \t in EBCDIC */
    case '\014':   /* $^L */
    case '\016':   /* $^N */
    case '\020':   /* $^P */
    case '\023':   /* $^S */
    case '\026':   /* $^V */
	if (len == 1)
	    goto yes;
	break;
    case '\024':   /* $^T, ${^TAINT} */
        if (len == 1 || strEQ(name, "\024AINT"))
            goto yes;
        break;
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
	if (len > 1) {
	    char *end = name + len;
	    while (--end > name) {
		if (!isDIGIT(*end))
		    return FALSE;
	    }
	}
    yes:
	return TRUE;
    default:
	break;
    }
    return FALSE;
}