[perl5.git] / mg.c

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

/*
 *  Sam sat on the ground and put his head in his hands.  'I wish I had never
 *  come here, and I don't want to see no more magic,' he said, and fell silent.
 *
 *     [p.363 of _The Lord of the Rings_, II/vii: "The Mirror of Galadriel"]
 */

/*
=head1 Magic
"Magic" is special data attached to SV structures in order to give them
"magical" properties.  When any Perl code tries to read from, or assign to,
an SV marked as magical, it calls the 'get' or 'set' function associated
with that SV's magic.  A get is called prior to reading an SV, in order to
give it a chance to update its internal value (get on $. writes the line
number of the last read filehandle into the SV's IV slot), while
set is called after an SV has been written to, in order to allow it to make
use of its changed value (set on $/ copies the SV's new value to the
PL_rs global variable).

Magic is implemented as a linked list of MAGIC structures attached to the
SV.  Each MAGIC struct holds the type of the magic, a pointer to an array
of functions that implement the get(), set(), length() etc functions,
plus space for some flags and pointers.  For example, a tied variable has
a MAGIC structure that contains a pointer to the object associated with the
tie.

=for apidoc Ayh||MAGIC

=cut

*/

#include "EXTERN.h"
#define PERL_IN_MG_C
#include "perl.h"
#include "feature.h"

#if defined(HAS_GETGROUPS) || defined(HAS_SETGROUPS)
#  ifdef I_GRP
#    include <grp.h>
#  endif
#endif

#if defined(HAS_SETGROUPS)
#  ifndef NGROUPS
#    define NGROUPS 32
#  endif
#endif

#ifdef __hpux
#  include <sys/pstat.h>
#endif

#ifdef HAS_PRCTL_SET_NAME
#  include <sys/prctl.h>
#endif

#ifdef __Lynx__
/* Missing protos on LynxOS */
void setruid(uid_t id);
void seteuid(uid_t id);
void setrgid(uid_t id);
void setegid(uid_t id);
#endif

/*
 * Pre-magic setup and post-magic takedown.
 * Use the "DESTRUCTOR" scope cleanup to reinstate magic.
 */

struct magic_state {
    SV* mgs_sv;
    I32 mgs_ss_ix;
    U32 mgs_flags;
    bool mgs_bumped;
};
/* MGS is typedef'ed to struct magic_state in perl.h */

STATIC void
S_save_magic_flags(pTHX_ I32 mgs_ix, SV *sv, U32 flags)
{
    MGS* mgs;
    bool bumped = FALSE;

    PERL_ARGS_ASSERT_SAVE_MAGIC_FLAGS;

    assert(SvMAGICAL(sv));

    /* we shouldn't really be called here with RC==0, but it can sometimes
     * happen via mg_clear() (which also shouldn't be called when RC==0,
     * but it can happen). Handle this case gracefully(ish) by not RC++
     * and thus avoiding the resultant double free */
    if (SvREFCNT(sv) > 0) {
    /* guard against sv getting freed midway through the mg clearing,
     * by holding a private reference for the duration. */
        SvREFCNT_inc_simple_void_NN(sv);
        bumped = TRUE;
    }

    SAVEDESTRUCTOR_X(S_restore_magic, INT2PTR(void*, (IV)mgs_ix));

    mgs = SSPTR(mgs_ix, MGS*);
    mgs->mgs_sv = sv;
    mgs->mgs_flags = SvMAGICAL(sv) | SvREADONLY(sv);
    mgs->mgs_ss_ix = PL_savestack_ix;   /* points after the saved destructor */
    mgs->mgs_bumped = bumped;

    SvFLAGS(sv) &= ~flags;
    SvREADONLY_off(sv);
}

#define save_magic(a,b) save_magic_flags(a,b,SVs_GMG|SVs_SMG|SVs_RMG)

/*
=for apidoc mg_magical

Turns on the magical status of an SV.  See C<L</sv_magic>>.

=cut
*/

void
Perl_mg_magical(SV *sv)
{
    const MAGIC* mg;
    PERL_ARGS_ASSERT_MG_MAGICAL;

    SvMAGICAL_off(sv);
    if ((mg = SvMAGIC(sv))) {
        do {
            const MGVTBL* const vtbl = mg->mg_virtual;
            if (vtbl) {
                if (vtbl->svt_get && !(mg->mg_flags & MGf_GSKIP))
                    SvGMAGICAL_on(sv);
                if (vtbl->svt_set)
                    SvSMAGICAL_on(sv);
                if (vtbl->svt_clear)
                    SvRMAGICAL_on(sv);
            }
        } while ((mg = mg->mg_moremagic));
        if (!(SvFLAGS(sv) & (SVs_GMG|SVs_SMG)))
            SvRMAGICAL_on(sv);
    }
}

/*
=for apidoc mg_get

Do magic before a value is retrieved from the SV.  The type of SV must
be >= C<SVt_PVMG>.  See C<L</sv_magic>>.

=cut
*/

int
Perl_mg_get(pTHX_ SV *sv)
{
    const I32 mgs_ix = SSNEW(sizeof(MGS));
    bool saved = FALSE;
    bool have_new = 0;
    bool taint_only = TRUE; /* the only get method seen is taint */
    MAGIC *newmg, *head, *cur, *mg;

    PERL_ARGS_ASSERT_MG_GET;

    if (PL_localizing == 1 && sv == DEFSV) return 0;

    /* We must call svt_get(sv, mg) for each valid entry in the linked
       list of magic. svt_get() may delete the current entry, add new
       magic to the head of the list, or upgrade the SV. AMS 20010810 */

    newmg = cur = head = mg = SvMAGIC(sv);
    while (mg) {
        const MGVTBL * const vtbl = mg->mg_virtual;
        MAGIC * const nextmg = mg->mg_moremagic;	/* it may delete itself */

        if (!(mg->mg_flags & MGf_GSKIP) && vtbl && vtbl->svt_get) {

            /* taint's mg get is so dumb it doesn't need flag saving */
            if (mg->mg_type != PERL_MAGIC_taint) {
                taint_only = FALSE;
                if (!saved) {
                    save_magic(mgs_ix, sv);
                    saved = TRUE;
                }
            }

            vtbl->svt_get(aTHX_ sv, mg);

            /* guard against magic having been deleted - eg FETCH calling
             * untie */
            if (!SvMAGIC(sv)) {
                /* recalculate flags */
                (SSPTR(mgs_ix, MGS *))->mgs_flags &= ~(SVs_GMG|SVs_SMG|SVs_RMG);
                break;
            }

            /* recalculate flags if this entry was deleted. */
            if (mg->mg_flags & MGf_GSKIP)
                (SSPTR(mgs_ix, MGS *))->mgs_flags &=
                     ~(SVs_GMG|SVs_SMG|SVs_RMG);
        }
        else if (vtbl == &PL_vtbl_utf8) {
            /* get-magic can reallocate the PV, unless there's only taint
             * magic */
            if (taint_only) {
                MAGIC *mg2;
                for (mg2 = nextmg; mg2; mg2 = mg2->mg_moremagic) {
                    if (   mg2->mg_type != PERL_MAGIC_taint
                        && !(mg2->mg_flags & MGf_GSKIP)
                        && mg2->mg_virtual
                        && mg2->mg_virtual->svt_get
                    ) {
                        taint_only = FALSE;
                        break;
                    }
                }
            }
            if (!taint_only)
                magic_setutf8(sv, mg);
        }

        mg = nextmg;

        if (have_new) {
            /* Have we finished with the new entries we saw? Start again
               where we left off (unless there are more new entries). */
            if (mg == head) {
                have_new = 0;
                mg   = cur;
                head = newmg;
            }
        }

        /* Were any new entries added? */
        if (!have_new && (newmg = SvMAGIC(sv)) != head) {
            have_new = 1;
            cur = mg;
            mg  = newmg;
            /* recalculate flags */
            (SSPTR(mgs_ix, MGS *))->mgs_flags &= ~(SVs_GMG|SVs_SMG|SVs_RMG);
        }
    }

    if (saved)
        restore_magic(INT2PTR(void *, (IV)mgs_ix));

    return 0;
}

/*
=for apidoc mg_set

Do magic after a value is assigned to the SV.  See C<L</sv_magic>>.

=cut
*/

int
Perl_mg_set(pTHX_ SV *sv)
{
    const I32 mgs_ix = SSNEW(sizeof(MGS));
    MAGIC* mg;
    MAGIC* nextmg;

    PERL_ARGS_ASSERT_MG_SET;

    if (PL_localizing == 2 && sv == DEFSV) return 0;

    save_magic_flags(mgs_ix, sv, SVs_GMG|SVs_SMG); /* leave SVs_RMG on */

    for (mg = SvMAGIC(sv); mg; mg = nextmg) {
        const MGVTBL* vtbl = mg->mg_virtual;
        nextmg = mg->mg_moremagic;	/* it may delete itself */
        if (mg->mg_flags & MGf_GSKIP) {
            mg->mg_flags &= ~MGf_GSKIP;	/* setting requires another read */
            (SSPTR(mgs_ix, MGS*))->mgs_flags &= ~(SVs_GMG|SVs_SMG|SVs_RMG);
        }
        if (PL_localizing == 2
            && PERL_MAGIC_TYPE_IS_VALUE_MAGIC(mg->mg_type))
            continue;
        if (vtbl && vtbl->svt_set)
            vtbl->svt_set(aTHX_ sv, mg);
    }

    restore_magic(INT2PTR(void*, (IV)mgs_ix));
    return 0;
}

I32
Perl_mg_size(pTHX_ SV *sv)
{
    MAGIC* mg;

    PERL_ARGS_ASSERT_MG_SIZE;

    for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
        const MGVTBL* const vtbl = mg->mg_virtual;
        if (vtbl && vtbl->svt_len) {
            const I32 mgs_ix = SSNEW(sizeof(MGS));
            I32 len;
            save_magic(mgs_ix, sv);
            /* omit MGf_GSKIP -- not changed here */
            len = vtbl->svt_len(aTHX_ sv, mg);
            restore_magic(INT2PTR(void*, (IV)mgs_ix));
            return len;
        }
    }

    switch(SvTYPE(sv)) {
        case SVt_PVAV:
            return AvFILLp((const AV *) sv); /* Fallback to non-tied array */
        case SVt_PVHV:
            /* FIXME */
        default:
            Perl_croak(aTHX_ "Size magic not implemented");

    }
    NOT_REACHED; /* NOTREACHED */
}

/*
=for apidoc mg_clear

Clear something magical that the SV represents.  See C<L</sv_magic>>.

=cut
*/

int
Perl_mg_clear(pTHX_ SV *sv)
{
    const I32 mgs_ix = SSNEW(sizeof(MGS));
    MAGIC* mg;
    MAGIC *nextmg;

    PERL_ARGS_ASSERT_MG_CLEAR;

    save_magic(mgs_ix, sv);

    for (mg = SvMAGIC(sv); mg; mg = nextmg) {
        const MGVTBL* const vtbl = mg->mg_virtual;
        /* omit GSKIP -- never set here */

        nextmg = mg->mg_moremagic; /* it may delete itself */

        if (vtbl && vtbl->svt_clear)
            vtbl->svt_clear(aTHX_ sv, mg);
    }

    restore_magic(INT2PTR(void*, (IV)mgs_ix));
    return 0;
}

static MAGIC*
S_mg_findext_flags(const SV *sv, int type, const MGVTBL *vtbl, U32 flags)
{
    assert(flags <= 1);

    if (sv) {
        MAGIC *mg;

        for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
            if (mg->mg_type == type && (!flags || mg->mg_virtual == vtbl)) {
                return mg;
            }
        }
    }

    return NULL;
}

/*
=for apidoc mg_find

Finds the magic pointer for C<type> matching the SV.  See C<L</sv_magic>>.

=cut
*/

MAGIC*
Perl_mg_find(const SV *sv, int type)
{
    return S_mg_findext_flags(sv, type, NULL, 0);
}

/*
=for apidoc mg_findext

Finds the magic pointer of C<type> with the given C<vtbl> for the C<SV>.  See
C<L</sv_magicext>>.

=cut
*/

MAGIC*
Perl_mg_findext(const SV *sv, int type, const MGVTBL *vtbl)
{
    return S_mg_findext_flags(sv, type, vtbl, 1);
}

MAGIC *
Perl_mg_find_mglob(pTHX_ SV *sv)
{
    PERL_ARGS_ASSERT_MG_FIND_MGLOB;
    if (SvTYPE(sv) == SVt_PVLV && LvTYPE(sv) == 'y') {
        /* This sv is only a delegate.  //g magic must be attached to
           its target. */
        vivify_defelem(sv);
        sv = LvTARG(sv);
    }
    if (SvTYPE(sv) >= SVt_PVMG && SvMAGIC(sv))
        return S_mg_findext_flags(sv, PERL_MAGIC_regex_global, 0, 0);
    return NULL;
}

/*
=for apidoc mg_copy

Copies the magic from one SV to another.  See C<L</sv_magic>>.

=cut
*/

int
Perl_mg_copy(pTHX_ SV *sv, SV *nsv, const char *key, I32 klen)
{
    int count = 0;
    MAGIC* mg;

    PERL_ARGS_ASSERT_MG_COPY;

    for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
        const MGVTBL* const vtbl = mg->mg_virtual;
        if ((mg->mg_flags & MGf_COPY) && vtbl->svt_copy){
            count += vtbl->svt_copy(aTHX_ sv, mg, nsv, key, klen);
        }
        else {
            const char type = mg->mg_type;
            if (isUPPER(type) && type != PERL_MAGIC_uvar) {
                sv_magic(nsv,
                     (type == PERL_MAGIC_tied)
                        ? SvTIED_obj(sv, mg)
                        : mg->mg_obj,
                     toLOWER(type), key, klen);
                count++;
            }
        }
    }
    return count;
}

/*
=for apidoc mg_localize

Copy some of the magic from an existing SV to new localized version of that
SV.  Container magic (I<e.g.>, C<%ENV>, C<$1>, C<tie>)
gets copied, value magic doesn't (I<e.g.>,
C<taint>, C<pos>).

If C<setmagic> is false then no set magic will be called on the new (empty) SV.
This typically means that assignment will soon follow (e.g. S<C<'local $x = $y'>>),
and that will handle the magic.

=cut
*/

void
Perl_mg_localize(pTHX_ SV *sv, SV *nsv, bool setmagic)
{
    MAGIC *mg;

    PERL_ARGS_ASSERT_MG_LOCALIZE;

    if (nsv == DEFSV)
        return;

    for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
        const MGVTBL* const vtbl = mg->mg_virtual;
        if (PERL_MAGIC_TYPE_IS_VALUE_MAGIC(mg->mg_type))
            continue;
                
        if ((mg->mg_flags & MGf_LOCAL) && vtbl->svt_local)
            (void)vtbl->svt_local(aTHX_ nsv, mg);
        else
            sv_magicext(nsv, mg->mg_obj, mg->mg_type, vtbl,
                            mg->mg_ptr, mg->mg_len);

        /* container types should remain read-only across localization */
        SvFLAGS(nsv) |= SvREADONLY(sv);
    }

    if (SvTYPE(nsv) >= SVt_PVMG && SvMAGIC(nsv)) {
        SvFLAGS(nsv) |= SvMAGICAL(sv);
        if (setmagic) {
            PL_localizing = 1;
            SvSETMAGIC(nsv);
            PL_localizing = 0;
        }
    }	    
}

#define mg_free_struct(sv, mg) S_mg_free_struct(aTHX_ sv, mg)
static void
S_mg_free_struct(pTHX_ SV *sv, MAGIC *mg)
{
    const MGVTBL* const vtbl = mg->mg_virtual;
    if (vtbl && vtbl->svt_free)
        vtbl->svt_free(aTHX_ sv, mg);

    if (mg->mg_len > 0)
        Safefree(mg->mg_ptr);
    else if (mg->mg_len == HEf_SVKEY)
        SvREFCNT_dec(MUTABLE_SV(mg->mg_ptr));

    if (mg->mg_flags & MGf_REFCOUNTED)
        SvREFCNT_dec(mg->mg_obj);
    Safefree(mg);
}

/*
=for apidoc mg_free

Free any magic storage used by the SV.  See C<L</sv_magic>>.

=cut
*/

int
Perl_mg_free(pTHX_ SV *sv)
{
    MAGIC* mg;
    MAGIC* moremagic;

    PERL_ARGS_ASSERT_MG_FREE;

    for (mg = SvMAGIC(sv); mg; mg = moremagic) {
        moremagic = mg->mg_moremagic;
        mg_free_struct(sv, mg);
        SvMAGIC_set(sv, moremagic);
    }
    SvMAGIC_set(sv, NULL);
    SvMAGICAL_off(sv);
    return 0;
}

/*
=for apidoc mg_free_type

Remove any magic of type C<how> from the SV C<sv>.  See L</sv_magic>.

=cut
*/

void
Perl_mg_free_type(pTHX_ SV *sv, int how)
{
    MAGIC *mg, *prevmg, *moremg;
    PERL_ARGS_ASSERT_MG_FREE_TYPE;
    for (prevmg = NULL, mg = SvMAGIC(sv); mg; prevmg = mg, mg = moremg) {
        moremg = mg->mg_moremagic;
        if (mg->mg_type == how) {
            MAGIC *newhead;
            /* temporarily move to the head of the magic chain, in case
               custom free code relies on this historical aspect of mg_free */
            if (prevmg) {
                prevmg->mg_moremagic = moremg;
                mg->mg_moremagic = SvMAGIC(sv);
                SvMAGIC_set(sv, mg);
            }
            newhead = mg->mg_moremagic;
            mg_free_struct(sv, mg);
            SvMAGIC_set(sv, newhead);
            mg = prevmg;
        }
    }
    mg_magical(sv);
}

/*
=for apidoc mg_freeext

Remove any magic of type C<how> using virtual table C<vtbl> from the
SV C<sv>.  See L</sv_magic>.

C<mg_freeext(sv, how, NULL)> is equivalent to C<mg_free_type(sv, how)>.

=cut
*/

void
Perl_mg_freeext(pTHX_ SV *sv, int how, const MGVTBL *vtbl)
{
    MAGIC *mg, *prevmg, *moremg;
    PERL_ARGS_ASSERT_MG_FREEEXT;
    for (prevmg = NULL, mg = SvMAGIC(sv); mg; prevmg = mg, mg = moremg) {
        MAGIC *newhead;
        moremg = mg->mg_moremagic;
        if (mg->mg_type == how && (vtbl == NULL || mg->mg_virtual == vtbl)) {
            /* temporarily move to the head of the magic chain, in case
               custom free code relies on this historical aspect of mg_free */
            if (prevmg) {
                prevmg->mg_moremagic = moremg;
                mg->mg_moremagic = SvMAGIC(sv);
                SvMAGIC_set(sv, mg);
            }
            newhead = mg->mg_moremagic;
            mg_free_struct(sv, mg);
            SvMAGIC_set(sv, newhead);
            mg = prevmg;
        }
    }
    mg_magical(sv);
}

#include <signal.h>

U32
Perl_magic_regdata_cnt(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_UNUSED_ARG(sv);

    PERL_ARGS_ASSERT_MAGIC_REGDATA_CNT;

    if (PL_curpm) {
        REGEXP * const rx = PM_GETRE(PL_curpm);
        if (rx) {
            const SSize_t n = (SSize_t)mg->mg_obj;
            if (n == '+') {          /* @+ */
                /* return the number possible */
                return RX_NPARENS(rx);
            } else {   /* @- @^CAPTURE  @{^CAPTURE} */
                I32 paren = RX_LASTPAREN(rx);

                /* return the last filled */
                while ( paren >= 0
                        && (RX_OFFS(rx)[paren].start == -1
                            || RX_OFFS(rx)[paren].end == -1) )
                    paren--;
                if (n == '-') {
                    /* @- */
                    return (U32)paren;
                } else {
                    /* @^CAPTURE @{^CAPTURE} */
                    return paren >= 0 ? (U32)(paren-1) : (U32)-1;
                }
            }
        }
    }

    return (U32)-1;
}

/* @-, @+ */

int
Perl_magic_regdatum_get(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_REGDATUM_GET;

    if (PL_curpm) {
        REGEXP * const rx = PM_GETRE(PL_curpm);
        if (rx) {
            const SSize_t n = (SSize_t)mg->mg_obj;
            /* @{^CAPTURE} does not contain $&, so we need to increment by 1 */
            const I32 paren = mg->mg_len
                            + (n == '\003' ? 1 : 0);
            SSize_t s;
            SSize_t t;
            if (paren < 0)
                return 0;
            if (paren <= (I32)RX_NPARENS(rx) &&
                (s = RX_OFFS(rx)[paren].start) != -1 &&
                (t = RX_OFFS(rx)[paren].end) != -1)
                {
                    SSize_t i;

                    if (n == '+')                /* @+ */
                        i = t;
                    else if (n == '-')           /* @- */
                        i = s;
                    else {                        /* @^CAPTURE @{^CAPTURE} */
                        CALLREG_NUMBUF_FETCH(rx,paren,sv);
                        return 0;
                    }

                    if (RX_MATCH_UTF8(rx)) {
                        const char * const b = RX_SUBBEG(rx);
                        if (b)
                            i = RX_SUBCOFFSET(rx) +
                                    utf8_length((U8*)b,
                                        (U8*)(b-RX_SUBOFFSET(rx)+i));
                    }

                    sv_setuv(sv, i);
                    return 0;
                }
        }
    }
    sv_set_undef(sv);
    return 0;
}

/* @-, @+ */

int
Perl_magic_regdatum_set(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_REGDATUM_SET;
    PERL_UNUSED_CONTEXT;
    PERL_UNUSED_ARG(sv);
    PERL_UNUSED_ARG(mg);
    Perl_croak_no_modify();
    NORETURN_FUNCTION_END;
}

#define SvRTRIM(sv) STMT_START {                \
    SV * sv_ = sv;                              \
    if (SvPOK(sv_)) {                           \
        STRLEN len = SvCUR(sv_);                \
        char * const p = SvPVX(sv_);            \
        while (len > 0 && isSPACE(p[len-1]))    \
           --len;                               \
        SvCUR_set(sv_, len);                    \
        p[len] = '\0';                          \
    }                                           \
} STMT_END

void
Perl_emulate_cop_io(pTHX_ const COP *const c, SV *const sv)
{
    PERL_ARGS_ASSERT_EMULATE_COP_IO;

    if (!(CopHINTS_get(c) & (HINT_LEXICAL_IO_IN|HINT_LEXICAL_IO_OUT)))
        sv_set_undef(sv);
    else {
        SvPVCLEAR(sv);
        SvUTF8_off(sv);
        if ((CopHINTS_get(c) & HINT_LEXICAL_IO_IN)) {
            SV *const value = cop_hints_fetch_pvs(c, "open<", 0);
            assert(value);
            sv_catsv(sv, value);
        }
        sv_catpvs(sv, "\0");
        if ((CopHINTS_get(c) & HINT_LEXICAL_IO_OUT)) {
            SV *const value = cop_hints_fetch_pvs(c, "open>", 0);
            assert(value);
            sv_catsv(sv, value);
        }
    }
}

STATIC void
S_fixup_errno_string(pTHX_ SV* sv)
{
    /* Do what is necessary to fixup the non-empty string in 'sv' for return to
     * Perl space. */

    PERL_ARGS_ASSERT_FIXUP_ERRNO_STRING;

    assert(SvOK(sv));

    if(strEQ(SvPVX(sv), "")) {
        sv_catpv(sv, UNKNOWN_ERRNO_MSG);
    }
}

/*
=for apidoc_section $errno
=for apidoc sv_string_from_errnum

Generates the message string describing an OS error and returns it as
an SV.  C<errnum> must be a value that C<errno> could take, identifying
the type of error.

If C<tgtsv> is non-null then the string will be written into that SV
(overwriting existing content) and it will be returned.  If C<tgtsv>
is a null pointer then the string will be written into a new mortal SV
which will be returned.

The message will be taken from whatever locale would be used by C<$!>,
and will be encoded in the SV in whatever manner would be used by C<$!>.
The details of this process are subject to future change.  Currently,
the message is taken from the C locale by default (usually producing an
English message), and from the currently selected locale when in the scope
of the C<use locale> pragma.  A heuristic attempt is made to decode the
message from the locale's character encoding, but it will only be decoded
as either UTF-8 or ISO-8859-1.  It is always correctly decoded in a UTF-8
locale, usually in an ISO-8859-1 locale, and never in any other locale.

The SV is always returned containing an actual string, and with no other
OK bits set.  Unlike C<$!>, a message is even yielded for C<errnum> zero
(meaning success), and if no useful message is available then a useless
string (currently empty) is returned.

=cut
*/

SV *
Perl_sv_string_from_errnum(pTHX_ int errnum, SV *tgtsv)
{
    char const *errstr;
    utf8ness_t utf8ness;

    if(!tgtsv)
        tgtsv = newSV_type_mortal(SVt_PV);
    errstr = my_strerror(errnum, &utf8ness);
    if(errstr) {
        sv_setpv(tgtsv, errstr);
        if (utf8ness == UTF8NESS_YES) {
            SvUTF8_on(tgtsv);
        }
        fixup_errno_string(tgtsv);
    } else {
        SvPVCLEAR(tgtsv);
    }
    return tgtsv;
}

#ifdef VMS
#include <descrip.h>
#include <starlet.h>
#endif

int
Perl_magic_get(pTHX_ SV *sv, MAGIC *mg)
{
    I32 paren;
    const char *s = NULL;
    REGEXP *rx;
    char nextchar;

    PERL_ARGS_ASSERT_MAGIC_GET;

    const char * const remaining = (mg->mg_ptr)
                                   ? mg->mg_ptr + 1
                                   : NULL;

    if (!mg->mg_ptr) {
        paren = mg->mg_len;
        if (PL_curpm && (rx = PM_GETRE(PL_curpm))) {
          do_numbuf_fetch:
            CALLREG_NUMBUF_FETCH(rx,paren,sv);
        }
        else
            goto set_undef;
        return 0;
    }

    nextchar = *remaining;
    switch (*mg->mg_ptr) {
    case '\001':		/* ^A */
        if (SvOK(PL_bodytarget)) sv_copypv(sv, PL_bodytarget);
        else
            sv_set_undef(sv);
        if (SvTAINTED(PL_bodytarget))
            SvTAINTED_on(sv);
        break;
    case '\003':		/* ^C, ^CHILD_ERROR_NATIVE */
        if (nextchar == '\0') {
            sv_setiv(sv, (IV)PL_minus_c);
        }
        else if (strEQ(remaining, "HILD_ERROR_NATIVE")) {
            sv_setiv(sv, (IV)STATUS_NATIVE);
        }
        break;

    case '\004':		/* ^D */
        sv_setiv(sv, (IV)(PL_debug & DEBUG_MASK));
        break;
    case '\005':  /* ^E */
         if (nextchar != '\0') {
            if (strEQ(remaining, "NCODING"))
                sv_set_undef(sv);
            break;
        }

#if defined(VMS) || defined(OS2) || defined(WIN32)
#   if defined(VMS)
        {
            char msg[255];
            $DESCRIPTOR(msgdsc,msg);
            sv_setnv(sv,(NV) vaxc$errno);
            if (sys$getmsg(vaxc$errno,&msgdsc.dsc$w_length,&msgdsc,0,0) & 1)
                sv_setpvn(sv,msgdsc.dsc$a_pointer,msgdsc.dsc$w_length);
            else
                SvPVCLEAR(sv);
        }
#elif defined(OS2)
        if (!(_emx_env & 0x200)) {	/* Under DOS */
            sv_setnv(sv, (NV)errno);
            if (errno) {
                utf8ness_t utf8ness;
                const char * errstr = my_strerror(errnum, &utf8ness);

                sv_setpv(sv, errstr);

                if (utf8ness == UTF8NESS_YES) {
                    SvUTF8_on(sv);
                }
            }
            else {
                SvPVCLEAR(sv);
            }
        } else {
            if (errno != errno_isOS2) {
                const int tmp = _syserrno();
                if (tmp)	/* 2nd call to _syserrno() makes it 0 */
                    Perl_rc = tmp;
            }
            sv_setnv(sv, (NV)Perl_rc);
            sv_setpv(sv, os2error(Perl_rc));
        }
        if (SvOK(sv) && strNE(SvPVX(sv), "")) {
            fixup_errno_string(sv);
        }
#   elif defined(WIN32)
        {
            const DWORD dwErr = GetLastError();
            sv_setnv(sv, (NV)dwErr);
            if (dwErr) {
                PerlProc_GetOSError(sv, dwErr);
                fixup_errno_string(sv);

#     ifdef USE_LOCALE
                if (   IN_LOCALE
                    && get_win32_message_utf8ness(SvPV_nomg_const_nolen(sv)))
                {
                    SvUTF8_on(sv);
                }
#     endif
            }
            else
                SvPVCLEAR(sv);
            SetLastError(dwErr);
        }
#   else
#   error Missing code for platform
#   endif
        SvRTRIM(sv);
        SvNOK_on(sv);	/* what a wonderful hack! */
        break;
#endif  /* End of platforms with special handling for $^E; others just fall
           through to $! */
    /* FALLTHROUGH */

    case '!':
        {
            dSAVE_ERRNO;
#ifdef VMS
            sv_setnv(sv, (NV)((errno == EVMSERR) ? vaxc$errno : errno));
#else
            sv_setnv(sv, (NV)errno);
#endif
#ifdef OS2
            if (errno == errno_isOS2 || errno == errno_isOS2_set)
                sv_setpv(sv, os2error(Perl_rc));
            else
#endif
            if (! errno) {
                SvPVCLEAR(sv);
            }
            else {
                sv_string_from_errnum(errno, sv);
                /* If no useful string is available, don't
                 * claim to have a string part.  The SvNOK_on()
                 * below will cause just the number part to be valid */
                if (!SvCUR(sv))
                    SvPOK_off(sv);
            }
            RESTORE_ERRNO;
        }

        SvRTRIM(sv);
        SvNOK_on(sv);	/* what a wonderful hack! */
        break;

    case '\006':		/* ^F */
        if (nextchar == '\0') {
            sv_setiv(sv, (IV)PL_maxsysfd);
        }
        break;
    case '\007':		/* ^GLOBAL_PHASE */
        if (strEQ(remaining, "LOBAL_PHASE")) {
            sv_setpvn(sv, PL_phase_names[PL_phase],
                      strlen(PL_phase_names[PL_phase]));
        }
        break;
    case '\010':		/* ^H */
        sv_setuv(sv, PL_hints);
        break;
    case '\011':		/* ^I */ /* NOT \t in EBCDIC */
        sv_setpv(sv, PL_inplace); /* Will undefine sv if PL_inplace is NULL */
        break;
    case '\014':		/* ^LAST_FH */
        if (strEQ(remaining, "AST_FH")) {
            if (PL_last_in_gv && (SV*)PL_last_in_gv != &PL_sv_undef) {
                assert(isGV_with_GP(PL_last_in_gv));
                sv_setrv_inc(sv, MUTABLE_SV(PL_last_in_gv));
                sv_rvweaken(sv);
            }
            else
                sv_set_undef(sv);
        }
        break;
    case '\017':		/* ^O & ^OPEN */
        if (nextchar == '\0') {
            sv_setpv(sv, PL_osname);
            SvTAINTED_off(sv);
        }
        else if (strEQ(remaining, "PEN")) {
            Perl_emulate_cop_io(aTHX_ &PL_compiling, sv);
        }
        break;
    case '\020':
        sv_setiv(sv, (IV)PL_perldb);
        break;
    case '\023':		/* ^S */
        if (nextchar == '\0') {
            if (PL_parser && PL_parser->lex_state != LEX_NOTPARSING)
                SvOK_off(sv);
            else if (PL_in_eval)
                sv_setiv(sv, PL_in_eval & ~(EVAL_INREQUIRE));
            else
                sv_setiv(sv, 0);
        }
        else if (strEQ(remaining, "AFE_LOCALES")) {

#if ! defined(USE_ITHREADS) || defined(USE_THREAD_SAFE_LOCALE)

            sv_setuv(sv, (UV) 1);

#else
            sv_setuv(sv, (UV) 0);

#endif

        }
        break;
    case '\024':		/* ^T */
        if (nextchar == '\0') {
#ifdef BIG_TIME
            sv_setnv(sv, PL_basetime);
#else
            sv_setiv(sv, (IV)PL_basetime);
#endif
        }
        else if (strEQ(remaining, "AINT"))
            sv_setiv(sv, TAINTING_get
                    ? (TAINT_WARN_get || PL_unsafe ? -1 : 1)
                    : 0);
        break;
    case '\025':		/* $^UNICODE, $^UTF8LOCALE, $^UTF8CACHE */
        if (strEQ(remaining, "NICODE"))
            sv_setuv(sv, (UV) PL_unicode);
        else if (strEQ(remaining, "TF8LOCALE"))
            sv_setuv(sv, (UV) PL_utf8locale);
        else if (strEQ(remaining, "TF8CACHE"))
            sv_setiv(sv, (IV) PL_utf8cache);
        break;
    case '\027':		/* ^W  & $^WARNING_BITS */
        if (nextchar == '\0')
            sv_setiv(sv, (IV)cBOOL(PL_dowarn & G_WARN_ON));
        else if (strEQ(remaining, "ARNING_BITS")) {
            if (PL_compiling.cop_warnings == pWARN_NONE) {
                sv_setpvn(sv, WARN_NONEstring, WARNsize) ;
            }
            else if (PL_compiling.cop_warnings == pWARN_STD) {
                goto set_undef;
            }
            else if (PL_compiling.cop_warnings == pWARN_ALL) {
                sv_setpvn(sv, WARN_ALLstring, WARNsize);
            }
            else {
                sv_setpvn(sv, (char *) (PL_compiling.cop_warnings + 1),
                          *PL_compiling.cop_warnings);
            }
        }
        break;
    case '+':
        if (PL_curpm && (rx = PM_GETRE(PL_curpm))) {
            paren = RX_LASTPAREN(rx);
            if (paren)
                goto do_numbuf_fetch;
        }
        goto set_undef;
    case '\016':		/* ^N */
        if (PL_curpm && (rx = PM_GETRE(PL_curpm))) {
            paren = RX_LASTCLOSEPAREN(rx);
            if (paren)
                goto do_numbuf_fetch;
        }
        goto set_undef;
    case '.':
        if (GvIO(PL_last_in_gv)) {
            sv_setiv(sv, (IV)IoLINES(GvIOp(PL_last_in_gv)));
        }
        break;
    case '?':
        {
            sv_setiv(sv, (IV)STATUS_CURRENT);
#ifdef COMPLEX_STATUS
            SvUPGRADE(sv, SVt_PVLV);
            LvTARGOFF(sv) = PL_statusvalue;
            LvTARGLEN(sv) = PL_statusvalue_vms;
#endif
        }
        break;
    case '^':
        if (GvIOp(PL_defoutgv))
                s = IoTOP_NAME(GvIOp(PL_defoutgv));
        if (s)
            sv_setpv(sv,s);
        else {
            sv_setpv(sv,GvENAME(PL_defoutgv));
            sv_catpvs(sv,"_TOP");
        }
        break;
    case '~':
        if (GvIOp(PL_defoutgv))
            s = IoFMT_NAME(GvIOp(PL_defoutgv));
        if (!s)
            s = GvENAME(PL_defoutgv);
        sv_setpv(sv,s);
        break;
    case '=':
        if (GvIO(PL_defoutgv))
            sv_setiv(sv, (IV)IoPAGE_LEN(GvIOp(PL_defoutgv)));
        break;
    case '-':
        if (GvIO(PL_defoutgv))
            sv_setiv(sv, (IV)IoLINES_LEFT(GvIOp(PL_defoutgv)));
        break;
    case '%':
        if (GvIO(PL_defoutgv))
            sv_setiv(sv, (IV)IoPAGE(GvIOp(PL_defoutgv)));
        break;
    case ':':
    case '/':
        break;
    case '[':
        sv_setiv(sv, 0);
        break;
    case '|':
        if (GvIO(PL_defoutgv))
            sv_setiv(sv, (IV)(IoFLAGS(GvIOp(PL_defoutgv)) & IOf_FLUSH) != 0 );
        break;
    case '\\':
        if (PL_ors_sv)
            sv_copypv(sv, PL_ors_sv);
        else
            goto set_undef;
        break;
    case '$': /* $$ */
        {
            IV const pid = (IV)PerlProc_getpid();
            if (isGV(mg->mg_obj) || SvIV(mg->mg_obj) != pid) {
                /* never set manually, or at least not since last fork */
                sv_setiv(sv, pid);
                /* never unsafe, even if reading in a tainted expression */
                SvTAINTED_off(sv);
            }
            /* else a value has been assigned manually, so do nothing */
        }
        break;
    case '<':
        sv_setuid(sv, PerlProc_getuid());
        break;
    case '>':
        sv_setuid(sv, PerlProc_geteuid());
        break;
    case '(':
        sv_setgid(sv, PerlProc_getgid());
        goto add_groups;
    case ')':
        sv_setgid(sv, PerlProc_getegid());
      add_groups:
#ifdef HAS_GETGROUPS
        {
            Groups_t *gary = NULL;
            I32 num_groups = getgroups(0, gary);
            if (num_groups > 0) {
                I32 i;
                Newx(gary, num_groups, Groups_t);
                num_groups = getgroups(num_groups, gary);
                for (i = 0; i < num_groups; i++)
                    Perl_sv_catpvf(aTHX_ sv, " %" IVdf, (IV)gary[i]);
                Safefree(gary);
            }
        }

        /*
            Set this to avoid warnings when the SV is used as a number.
            Avoid setting the public IOK flag so that serializers will
            use the PV.
        */
        (void)SvIOKp_on(sv);	/* what a wonderful hack! */
#endif
        break;
    case '0':
        break;
    }
    return 0;

  set_undef:
    sv_set_undef(sv);
    return 0;
}

int
Perl_magic_getuvar(pTHX_ SV *sv, MAGIC *mg)
{
    struct ufuncs * const uf = (struct ufuncs *)mg->mg_ptr;

    PERL_ARGS_ASSERT_MAGIC_GETUVAR;

    if (uf && uf->uf_val)
        (*uf->uf_val)(aTHX_ uf->uf_index, sv);
    return 0;
}

int
Perl_magic_setenv(pTHX_ SV *sv, MAGIC *mg)
{
    STRLEN len = 0, klen;

    const char *key;
    const char *s = "";

    SV *keysv = MgSV(mg);

    if (keysv == NULL) {
        key = mg->mg_ptr;
        klen = mg->mg_len;
    }
    else {
        if (!sv_utf8_downgrade(keysv, /* fail_ok */ TRUE)) {
            Perl_ck_warner_d(aTHX_ packWARN(WARN_UTF8), "Wide character in %s", "setenv key (encoding to utf8)");
        }

        key = SvPV_const(keysv,klen);
    }

    PERL_ARGS_ASSERT_MAGIC_SETENV;

    SvGETMAGIC(sv);
    if (SvOK(sv)) {
        /* defined environment variables are byte strings; unfortunately
           there is no SvPVbyte_force_nomg(), so we must do this piecewise */
        (void)SvPV_force_nomg_nolen(sv);
        (void)sv_utf8_downgrade(sv, /* fail_ok */ TRUE);
        if (SvUTF8(sv)) {
            Perl_ck_warner_d(aTHX_ packWARN(WARN_UTF8), "Wide character in %s", "setenv");
            SvUTF8_off(sv);
        }
        s = SvPVX(sv);
        len = SvCUR(sv);
    }
    my_setenv(key, s); /* does the deed */

#ifdef DYNAMIC_ENV_FETCH
     /* We just undefd an environment var.  Is a replacement */
     /* waiting in the wings? */
    if (!len) {
        SV ** const valp = hv_fetch(GvHVn(PL_envgv), key, klen, FALSE);
        if (valp)
            s = SvOK(*valp) ? SvPV_const(*valp, len) : "";
    }
#endif

#if !defined(OS2) && !defined(WIN32)
                            /* And you'll never guess what the dog had */
                            /*   in its mouth... */
    if (TAINTING_get) {
        MgTAINTEDDIR_off(mg);
#ifdef VMS
        if (s && memEQs(key, klen, "DCL$PATH")) {
            char pathbuf[256], eltbuf[256], *cp, *elt;
            int i = 0, j = 0;

            my_strlcpy(eltbuf, s, sizeof(eltbuf));
            elt = eltbuf;
            do {          /* DCL$PATH may be a search list */
                while (1) {   /* as may dev portion of any element */
                    if ( ((cp = strchr(elt,'[')) || (cp = strchr(elt,'<'))) ) {
                        if ( *(cp+1) == '.' || *(cp+1) == '-' ||
                             cando_by_name(S_IWUSR,0,elt) ) {
                            MgTAINTEDDIR_on(mg);
                            return 0;
                        }
                    }
                    if ((cp = strchr(elt, ':')) != NULL)
                        *cp = '\0';
                    if (my_trnlnm(elt, eltbuf, j++))
                        elt = eltbuf;
                    else
                        break;
                }
                j = 0;
            } while (my_trnlnm(s, pathbuf, i++) && (elt = pathbuf));
        }
#endif /* VMS */
        if (s && memEQs(key, klen, "PATH")) {
            const char * const strend = s + len;
#ifdef __VMS  /* Hmm.  How do we get $Config{path_sep} from C? */
            const char path_sep = PL_perllib_sep;
#else
            const char path_sep = ':';
#endif

#ifndef __VMS
            /* Does this apply for VMS?
             * Empty PATH on linux is treated same as ".", which is forbidden
             * under taint. So check if the PATH variable is empty. */
            if (!len) {
                MgTAINTEDDIR_on(mg);
                return 0;
            }
#endif
            /* set MGf_TAINTEDDIR if any component of the new path is
             * relative or world-writeable */
            while (s < strend) {
                char tmpbuf[256];
                Stat_t st;
                I32 i;
                s = delimcpy_no_escape(tmpbuf, tmpbuf + sizeof tmpbuf,
                             s, strend, path_sep, &i);
                s++;
                if (i >= (I32)sizeof tmpbuf   /* too long -- assume the worst */
#ifdef __VMS
                      /* no colon thus no device name -- assume relative path */
                      || (PL_perllib_sep != ':' && !strchr(tmpbuf, ':'))
                      /* Using Unix separator, e.g. under bash, so act line Unix */
                      || (PL_perllib_sep == ':' && *tmpbuf != '/')
#else
                      || *tmpbuf != '/' /* no starting slash -- assume relative path */
                      || s == strend    /* trailing empty component -- same as "." */
#endif
                      || (PerlLIO_stat(tmpbuf, &st) == 0 && (st.st_mode & 2)) ) {
                    MgTAINTEDDIR_on(mg);
                    return 0;
                }
            }
        }
    }
#endif /* neither OS2 nor WIN32 */

    return 0;
}

int
Perl_magic_clearenv(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEARENV;
    PERL_UNUSED_ARG(sv);
    my_setenv(MgPV_nolen_const(mg),NULL);
    return 0;
}

int
Perl_magic_set_all_env(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SET_ALL_ENV;
    PERL_UNUSED_ARG(mg);
#if defined(VMS)
    Perl_die(aTHX_ "Can't make list assignment to %%ENV on this system");
#else
    if (PL_localizing) {
        HE* entry;
        my_clearenv();
        hv_iterinit(MUTABLE_HV(sv));
        while ((entry = hv_iternext(MUTABLE_HV(sv)))) {
            I32 keylen;
            my_setenv(hv_iterkey(entry, &keylen),
                      SvPV_nolen_const(hv_iterval(MUTABLE_HV(sv), entry)));
        }
    }
#endif
    return 0;
}

int
Perl_magic_clear_all_env(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEAR_ALL_ENV;
    PERL_UNUSED_ARG(sv);
    PERL_UNUSED_ARG(mg);
#if defined(VMS)
    Perl_die(aTHX_ "Can't make list assignment to %%ENV on this system");
#else
    my_clearenv();
#endif
    return 0;
}

#ifndef PERL_MICRO
#ifdef HAS_SIGPROCMASK
static void
restore_sigmask(pTHX_ SV *save_sv)
{
    const sigset_t * const ossetp = (const sigset_t *) SvPV_nolen_const( save_sv );
    (void)sigprocmask(SIG_SETMASK, ossetp, NULL);
}
#endif
int
Perl_magic_getsig(pTHX_ SV *sv, MAGIC *mg)
{
    /* Are we fetching a signal entry? */
    int i = (I16)mg->mg_private;

    PERL_ARGS_ASSERT_MAGIC_GETSIG;

    if (!i) {
        STRLEN siglen;
        const char * sig = MgPV_const(mg, siglen);
        mg->mg_private = i = whichsig_pvn(sig, siglen);
    }

    if (i > 0) {
        if(PL_psig_ptr[i])
            sv_setsv(sv,PL_psig_ptr[i]);
        else {
            Sighandler_t sigstate = rsignal_state(i);
#ifdef FAKE_PERSISTENT_SIGNAL_HANDLERS
            if (PL_sig_handlers_initted && PL_sig_ignoring[i])
                sigstate = SIG_IGN;
#endif
#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
            if (PL_sig_handlers_initted && PL_sig_defaulting[i])
                sigstate = SIG_DFL;
#endif
            /* cache state so we don't fetch it again */
            if(sigstate == (Sighandler_t) SIG_IGN)
                sv_setpvs(sv,"IGNORE");
            else
                sv_set_undef(sv);
            PL_psig_ptr[i] = SvREFCNT_inc_simple_NN(sv);
            SvTEMP_off(sv);
        }
    }
    return 0;
}
int
Perl_magic_clearsig(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEARSIG;

    magic_setsig(NULL, mg);
    return sv_unmagic(sv, mg->mg_type);
}


#ifdef PERL_USE_3ARG_SIGHANDLER
Signal_t
Perl_csighandler(int sig, Siginfo_t *sip, void *uap)
{
    Perl_csighandler3(sig, sip, uap);
}
#else
Signal_t
Perl_csighandler(int sig)
{
    Perl_csighandler3(sig, NULL, NULL);
}
#endif

Signal_t
Perl_csighandler1(int sig)
{
    Perl_csighandler3(sig, NULL, NULL);
}

/* Handler intended to directly handle signal calls from the kernel.
 * (Depending on configuration, the kernel may actually call one of the
 * wrappers csighandler() or csighandler1() instead.)
 * It either queues up the signal or dispatches it immediately depending
 * on whether safe signals are enabled and whether the signal is capable
 * of being deferred (e.g. SEGV isn't).
 */

Signal_t
Perl_csighandler3(int sig, Siginfo_t *sip PERL_UNUSED_DECL, void *uap PERL_UNUSED_DECL)
{
#ifdef PERL_GET_SIG_CONTEXT
    dTHXa(PERL_GET_SIG_CONTEXT);
#else
    dTHX;
#endif

#ifdef PERL_USE_3ARG_SIGHANDLER
#if defined(__cplusplus) && defined(__GNUC__)
    /* g++ doesn't support PERL_UNUSED_DECL, so the sip and uap
     * parameters would be warned about. */
    PERL_UNUSED_ARG(sip);
    PERL_UNUSED_ARG(uap);
#endif
#endif

#ifdef FAKE_PERSISTENT_SIGNAL_HANDLERS
    (void) rsignal(sig, PL_csighandlerp);
    if (PL_sig_ignoring[sig]) return;
#endif
#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
    if (PL_sig_defaulting[sig])
#ifdef KILL_BY_SIGPRC
            exit((Perl_sig_to_vmscondition(sig)&STS$M_COND_ID)|STS$K_SEVERE|STS$M_INHIB_MSG);
#else
            exit(1);
#endif
#endif
    if (
#ifdef SIGILL
           sig == SIGILL ||
#endif
#ifdef SIGBUS
           sig == SIGBUS ||
#endif
#ifdef SIGSEGV
           sig == SIGSEGV ||
#endif
#ifdef SIGFPE
           sig == SIGFPE ||
#endif
           (PL_signals & PERL_SIGNALS_UNSAFE_FLAG))
        /* Call the perl level handler now--
         * with risk we may be in malloc() or being destructed etc. */
    {
        if (PL_sighandlerp == Perl_sighandler)
            /* default handler, so can call perly_sighandler() directly
             * rather than via Perl_sighandler, passing the extra
             * 'safe = false' arg
             */
            Perl_perly_sighandler(sig, NULL, NULL, 0 /* unsafe */);
        else
#ifdef PERL_USE_3ARG_SIGHANDLER
            (*PL_sighandlerp)(sig, NULL, NULL);
#else
            (*PL_sighandlerp)(sig);
#endif
    }
    else {
        if (!PL_psig_pend) return;
        /* Set a flag to say this signal is pending, that is awaiting delivery after
         * the current Perl opcode completes */
        PL_psig_pend[sig]++;

#ifndef SIG_PENDING_DIE_COUNT
#  define SIG_PENDING_DIE_COUNT 120
#endif
        /* Add one to say _a_ signal is pending */
        if (++PL_sig_pending >= SIG_PENDING_DIE_COUNT)
            Perl_croak(aTHX_ "Maximal count of pending signals (%lu) exceeded",
                       (unsigned long)SIG_PENDING_DIE_COUNT);
    }
}

#if defined(FAKE_PERSISTENT_SIGNAL_HANDLERS) || defined(FAKE_DEFAULT_SIGNAL_HANDLERS)
void
Perl_csighandler_init(void)
{
    int sig;
    if (PL_sig_handlers_initted) return;

    for (sig = 1; sig < SIG_SIZE; sig++) {
#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
        dTHX;
        PL_sig_defaulting[sig] = 1;
        (void) rsignal(sig, PL_csighandlerp);
#endif
#ifdef FAKE_PERSISTENT_SIGNAL_HANDLERS
        PL_sig_ignoring[sig] = 0;
#endif
    }
    PL_sig_handlers_initted = 1;
}
#endif

#if defined HAS_SIGPROCMASK
static void
unblock_sigmask(pTHX_ void* newset)
{
    PERL_UNUSED_CONTEXT;
    sigprocmask(SIG_UNBLOCK, (sigset_t*)newset, NULL);
}
#endif

void
Perl_despatch_signals(pTHX)
{
    int sig;
    PL_sig_pending = 0;
    for (sig = 1; sig < SIG_SIZE; sig++) {
        if (PL_psig_pend[sig]) {
            dSAVE_ERRNO;
#ifdef HAS_SIGPROCMASK
            /* From sigaction(2) (FreeBSD man page):
             * | Signal routines normally execute with the signal that
             * | caused their invocation blocked, but other signals may
             * | yet occur.
             * Emulation of this behavior (from within Perl) is enabled
             * using sigprocmask
             */
            int was_blocked;
            sigset_t newset, oldset;

            sigemptyset(&newset);
            sigaddset(&newset, sig);
            sigprocmask(SIG_BLOCK, &newset, &oldset);
            was_blocked = sigismember(&oldset, sig);
            if (!was_blocked) {
                SV* save_sv = newSVpvn((char *)(&newset), sizeof(sigset_t));
                ENTER;
                SAVEFREESV(save_sv);
                SAVEDESTRUCTOR_X(unblock_sigmask, SvPV_nolen(save_sv));
            }
#endif
            PL_psig_pend[sig] = 0;
            if (PL_sighandlerp == Perl_sighandler)
                /* default handler, so can call perly_sighandler() directly
                 * rather than via Perl_sighandler, passing the extra
                 * 'safe = true' arg
                 */
                Perl_perly_sighandler(sig, NULL, NULL, 1 /* safe */);
            else
#ifdef PERL_USE_3ARG_SIGHANDLER
                (*PL_sighandlerp)(sig, NULL, NULL);
#else
                (*PL_sighandlerp)(sig);
#endif

#ifdef HAS_SIGPROCMASK
            if (!was_blocked)
                LEAVE;
#endif
            RESTORE_ERRNO;
        }
    }
}

/* sv of NULL signifies that we're acting as magic_clearsig.  */
int
Perl_magic_setsig(pTHX_ SV *sv, MAGIC *mg)
{
    I32 i;
    SV** svp = NULL;
    /* Need to be careful with SvREFCNT_dec(), because that can have side
     * effects (due to closures). We must make sure that the new disposition
     * is in place before it is called.
     */
    SV* to_dec = NULL;
    STRLEN len;
#ifdef HAS_SIGPROCMASK
    sigset_t set, save;
    SV* save_sv;
#endif
    const char *s = MgPV_const(mg,len);

    PERL_ARGS_ASSERT_MAGIC_SETSIG;

    if (*s == '_') {
        if (memEQs(s, len, "__DIE__"))
            svp = &PL_diehook;
        else if (memEQs(s, len, "__WARN__")
                 && (sv ? 1 : PL_warnhook != PERL_WARNHOOK_FATAL)) {
            /* Merge the existing behaviours, which are as follows:
               magic_setsig, we always set svp to &PL_warnhook
               (hence we always change the warnings handler)
               For magic_clearsig, we don't change the warnings handler if it's
               set to the &PL_warnhook.  */
            svp = &PL_warnhook;
        } else if (sv) {
            SV *tmp = sv_newmortal();
            Perl_croak(aTHX_ "No such hook: %s",
                                pv_pretty(tmp, s, len, 0, NULL, NULL, 0));
        }
        i = 0;
        if (svp && *svp) {
            if (*svp != PERL_WARNHOOK_FATAL)
                to_dec = *svp;
            *svp = NULL;
        }
    }
    else {
        i = (I16)mg->mg_private;
        if (!i) {
            i = whichsig_pvn(s, len);   /* ...no, a brick */
            mg->mg_private = (U16)i;
        }
        if (i <= 0) {
            if (sv) {
                SV *tmp = sv_newmortal();
                Perl_ck_warner(aTHX_ packWARN(WARN_SIGNAL), "No such signal: SIG%s",
                                            pv_pretty(tmp, s, len, 0, NULL, NULL, 0));
            }
            return 0;
        }
#ifdef HAS_SIGPROCMASK
        /* Avoid having the signal arrive at a bad time, if possible. */
        sigemptyset(&set);
        sigaddset(&set,i);
        sigprocmask(SIG_BLOCK, &set, &save);
        ENTER;
        save_sv = newSVpvn((char *)(&save), sizeof(sigset_t));
        SAVEFREESV(save_sv);
        SAVEDESTRUCTOR_X(restore_sigmask, save_sv);
#endif
        PERL_ASYNC_CHECK();
#if defined(FAKE_PERSISTENT_SIGNAL_HANDLERS) || defined(FAKE_DEFAULT_SIGNAL_HANDLERS)
        if (!PL_sig_handlers_initted) Perl_csighandler_init();
#endif
#ifdef FAKE_PERSISTENT_SIGNAL_HANDLERS
        PL_sig_ignoring[i] = 0;
#endif
#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
        PL_sig_defaulting[i] = 0;
#endif
        to_dec = PL_psig_ptr[i];
        if (sv) {
            PL_psig_ptr[i] = SvREFCNT_inc_simple_NN(sv);
            SvTEMP_off(sv); /* Make sure it doesn't go away on us */

            /* Signals don't change name during the program's execution, so once
               they're cached in the appropriate slot of PL_psig_name, they can
               stay there.

               Ideally we'd find some way of making SVs at (C) compile time, or
               at least, doing most of the work.  */
            if (!PL_psig_name[i]) {
                const char* name = PL_sig_name[i];
                PL_psig_name[i] = newSVpvn(name, strlen(name));
                SvREADONLY_on(PL_psig_name[i]);
            }
        } else {
            SvREFCNT_dec(PL_psig_name[i]);
            PL_psig_name[i] = NULL;
            PL_psig_ptr[i] = NULL;
        }
    }
    if (sv && (isGV_with_GP(sv) || SvROK(sv))) {
        if (i) {
            (void)rsignal(i, PL_csighandlerp);
        }
        else
            *svp = SvREFCNT_inc_simple_NN(sv);
    } else {
        if (sv && SvOK(sv)) {
            s = SvPV_force(sv, len);
        } else {
            sv = NULL;
        }
        if (sv && memEQs(s, len,"IGNORE")) {
            if (i) {
#ifdef FAKE_PERSISTENT_SIGNAL_HANDLERS
                PL_sig_ignoring[i] = 1;
                (void)rsignal(i, PL_csighandlerp);
#else
                (void)rsignal(i, (Sighandler_t) SIG_IGN);
#endif
            }
        }
        else if (!sv || memEQs(s, len,"DEFAULT") || !len) {
            if (i) {
#ifdef FAKE_DEFAULT_SIGNAL_HANDLERS
                PL_sig_defaulting[i] = 1;
                (void)rsignal(i, PL_csighandlerp);
#else
                (void)rsignal(i, (Sighandler_t) SIG_DFL);
#endif
            }
        }
        else {
            /*
             * We should warn if HINT_STRICT_REFS, but without
             * access to a known hint bit in a known OP, we can't
             * tell whether HINT_STRICT_REFS is in force or not.
             */
            if (!memchr(s, ':', len) && !memchr(s, '\'', len))
                Perl_sv_insert_flags(aTHX_ sv, 0, 0, STR_WITH_LEN("main::"),
                                     SV_GMAGIC);
            if (i)
                (void)rsignal(i, PL_csighandlerp);
            else
                *svp = SvREFCNT_inc_simple_NN(sv);
        }
    }

#ifdef HAS_SIGPROCMASK
    if(i)
        LEAVE;
#endif
    SvREFCNT_dec(to_dec);
    return 0;
}
#endif /* !PERL_MICRO */

int
Perl_magic_setsigall(pTHX_ SV* sv, MAGIC* mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETSIGALL;
    PERL_UNUSED_ARG(mg);

    if (PL_localizing == 2) {
        HV* hv = (HV*)sv;
        HE* current;
        hv_iterinit(hv);
        while ((current = hv_iternext(hv))) {
            SV* sigelem = hv_iterval(hv, current);
            mg_set(sigelem);
        }
    }
    return 0;
}

int
Perl_magic_setisa(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETISA;
    PERL_UNUSED_ARG(sv);

    /* Skip _isaelem because _isa will handle it shortly */
    if (PL_delaymagic & DM_ARRAY_ISA && mg->mg_type == PERL_MAGIC_isaelem)
        return 0;

    return magic_clearisa(NULL, mg);
}

/* sv of NULL signifies that we're acting as magic_setisa.  */
int
Perl_magic_clearisa(pTHX_ SV *sv, MAGIC *mg)
{
    HV* stash;
    PERL_ARGS_ASSERT_MAGIC_CLEARISA;

    /* Bail out if destruction is going on */
    if(PL_phase == PERL_PHASE_DESTRUCT) return 0;

    if (sv)
        av_clear(MUTABLE_AV(sv));

    if (SvTYPE(mg->mg_obj) != SVt_PVGV && SvSMAGICAL(mg->mg_obj))
        /* This occurs with setisa_elem magic, which calls this
           same function. */
        mg = mg_find(mg->mg_obj, PERL_MAGIC_isa);

    assert(mg);
    if (SvTYPE(mg->mg_obj) == SVt_PVAV) { /* multiple stashes */
        SV **svp = AvARRAY((AV *)mg->mg_obj);
        I32 items = AvFILLp((AV *)mg->mg_obj) + 1;
        while (items--) {
            stash = GvSTASH((GV *)*svp++);
            if (stash && HvENAME(stash)) mro_isa_changed_in(stash);
        }

        return 0;
    }

    stash = GvSTASH(
        (const GV *)mg->mg_obj
    );

    /* The stash may have been detached from the symbol table, so check its
       name before doing anything. */
    if (stash && HvENAME_get(stash))
        mro_isa_changed_in(stash);

    return 0;
}

int
Perl_magic_getnkeys(pTHX_ SV *sv, MAGIC *mg)
{
    HV * const hv = MUTABLE_HV(LvTARG(sv));
    I32 i = 0;

    PERL_ARGS_ASSERT_MAGIC_GETNKEYS;
    PERL_UNUSED_ARG(mg);

    if (hv) {
         (void) hv_iterinit(hv);
         if (! SvTIED_mg((const SV *)hv, PERL_MAGIC_tied))
             i = HvUSEDKEYS(hv);
         else {
             while (hv_iternext(hv))
                 i++;
         }
    }

    sv_setiv(sv, (IV)i);
    return 0;
}

int
Perl_magic_setnkeys(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETNKEYS;
    PERL_UNUSED_ARG(mg);
    if (LvTARG(sv)) {
        hv_ksplit(MUTABLE_HV(LvTARG(sv)), SvIV(sv));
    }
    return 0;
}

/*
=for apidoc_section $magic
=for apidoc magic_methcall

Invoke a magic method (like FETCH).

C<sv> and C<mg> are the tied thingy and the tie magic.

C<meth> is the name of the method to call.

C<argc> is the number of args (in addition to $self) to pass to the method.

The C<flags> can be:

    G_DISCARD     invoke method with G_DISCARD flag and don't
                  return a value
    G_UNDEF_FILL  fill the stack with argc pointers to
                  PL_sv_undef

The arguments themselves are any values following the C<flags> argument.

Returns the SV (if any) returned by the method, or C<NULL> on failure.


=cut
*/

SV*
Perl_magic_methcall(pTHX_ SV *sv, const MAGIC *mg, SV *meth, U32 flags,
                    U32 argc, ...)
{
    dSP;
    SV* ret = NULL;

    PERL_ARGS_ASSERT_MAGIC_METHCALL;

    ENTER;

    if (flags & G_WRITING_TO_STDERR) {
        SAVETMPS;

        save_re_context();
        SAVESPTR(PL_stderrgv);
        PL_stderrgv = NULL;
    }

    PUSHSTACKi(PERLSI_MAGIC);
    PUSHMARK(SP);

    /* EXTEND() expects a signed argc; don't wrap when casting */
    assert(argc <= I32_MAX);
    EXTEND(SP, (I32)argc+1);
    PUSHs(SvTIED_obj(sv, mg));
    if (flags & G_UNDEF_FILL) {
        while (argc--) {
            PUSHs(&PL_sv_undef);
        }
    } else if (argc > 0) {
        va_list args;
        va_start(args, argc);

        do {
            SV *const this_sv = va_arg(args, SV *);
            PUSHs(this_sv);
        } while (--argc);

        va_end(args);
    }
    PUTBACK;
    if (flags & G_DISCARD) {
        call_sv(meth, G_SCALAR|G_DISCARD|G_METHOD_NAMED);
    }
    else {
        if (call_sv(meth, G_SCALAR|G_METHOD_NAMED))
            ret = *PL_stack_sp--;
    }
    POPSTACK;
    if (flags & G_WRITING_TO_STDERR)
        FREETMPS;
    LEAVE;
    return ret;
}

/* wrapper for magic_methcall that creates the first arg */

STATIC SV*
S_magic_methcall1(pTHX_ SV *sv, const MAGIC *mg, SV *meth, U32 flags,
    int n, SV *val)
{
    SV* arg1 = NULL;

    PERL_ARGS_ASSERT_MAGIC_METHCALL1;

    if (mg->mg_ptr) {
        if (mg->mg_len >= 0) {
            arg1 = newSVpvn_flags(mg->mg_ptr, mg->mg_len, SVs_TEMP);
        }
        else if (mg->mg_len == HEf_SVKEY)
            arg1 = MUTABLE_SV(mg->mg_ptr);
    }
    else if (mg->mg_type == PERL_MAGIC_tiedelem) {
        arg1 = newSViv((IV)(mg->mg_len));
        sv_2mortal(arg1);
    }
    if (!arg1) {
        return Perl_magic_methcall(aTHX_ sv, mg, meth, flags, n - 1, val);
    }
    return Perl_magic_methcall(aTHX_ sv, mg, meth, flags, n, arg1, val);
}

STATIC int
S_magic_methpack(pTHX_ SV *sv, const MAGIC *mg, SV *meth)
{
    SV* ret;

    PERL_ARGS_ASSERT_MAGIC_METHPACK;

    ret = magic_methcall1(sv, mg, meth, 0, 1, NULL);
    if (ret)
        sv_setsv(sv, ret);
    return 0;
}

int
Perl_magic_getpack(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_GETPACK;

    if (mg->mg_type == PERL_MAGIC_tiedelem)
        mg->mg_flags |= MGf_GSKIP;
    magic_methpack(sv,mg,SV_CONST(FETCH));
    return 0;
}

int
Perl_magic_setpack(pTHX_ SV *sv, MAGIC *mg)
{
    MAGIC *tmg;
    SV    *val;

    PERL_ARGS_ASSERT_MAGIC_SETPACK;

    /* in the code C<$tied{foo} = $val>, the "thing" that gets passed to
     * STORE() is not $val, but rather a PVLV (the sv in this call), whose
     * public flags indicate its value based on copying from $val. Doing
     * mg_set() on the PVLV temporarily does SvMAGICAL_off(), then calls us.
     * So STORE()'s $_[2] arg is a temporarily disarmed PVLV. This goes
     * wrong if $val happened to be tainted, as sv hasn't got magic
     * enabled, even though taint magic is in the chain. In which case,
     * fake up a temporary tainted value (this is easier than temporarily
     * re-enabling magic on sv). */

    if (TAINTING_get && (tmg = mg_find(sv, PERL_MAGIC_taint))
        && (tmg->mg_len & 1))
    {
        val = sv_mortalcopy(sv);
        SvTAINTED_on(val);
    }
    else
        val = sv;

    magic_methcall1(sv, mg, SV_CONST(STORE), G_DISCARD, 2, val);
    return 0;
}

int
Perl_magic_clearpack(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEARPACK;

    if (mg->mg_type == PERL_MAGIC_tiedscalar) return 0;
    return magic_methpack(sv,mg,SV_CONST(DELETE));
}


U32
Perl_magic_sizepack(pTHX_ SV *sv, MAGIC *mg)
{
    I32 retval = 0;
    SV* retsv;

    PERL_ARGS_ASSERT_MAGIC_SIZEPACK;

    retsv = magic_methcall1(sv, mg, SV_CONST(FETCHSIZE), 0, 1, NULL);
    if (retsv) {
        retval = SvIV(retsv)-1;
        if (retval < -1)
            Perl_croak(aTHX_ "FETCHSIZE returned a negative value");
    }
    return (U32) retval;
}

int
Perl_magic_wipepack(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_WIPEPACK;

    Perl_magic_methcall(aTHX_ sv, mg, SV_CONST(CLEAR), G_DISCARD, 0);
    return 0;
}

int
Perl_magic_nextpack(pTHX_ SV *sv, MAGIC *mg, SV *key)
{
    SV* ret;

    PERL_ARGS_ASSERT_MAGIC_NEXTPACK;

    ret = SvOK(key) ? Perl_magic_methcall(aTHX_ sv, mg, SV_CONST(NEXTKEY), 0, 1, key)
        : Perl_magic_methcall(aTHX_ sv, mg, SV_CONST(FIRSTKEY), 0, 0);
    if (ret)
        sv_setsv(key,ret);
    return 0;
}

int
Perl_magic_existspack(pTHX_ SV *sv, const MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_EXISTSPACK;

    return magic_methpack(sv,mg,SV_CONST(EXISTS));
}

SV *
Perl_magic_scalarpack(pTHX_ HV *hv, MAGIC *mg)
{
    SV *retval;
    SV * const tied = SvTIED_obj(MUTABLE_SV(hv), mg);
    HV * const pkg = SvSTASH((const SV *)SvRV(tied));
   
    PERL_ARGS_ASSERT_MAGIC_SCALARPACK;

    if (!gv_fetchmethod_autoload(pkg, "SCALAR", FALSE)) {
        SV *key;
        if (HvEITER_get(hv))
            /* we are in an iteration so the hash cannot be empty */
            return &PL_sv_yes;
        /* no xhv_eiter so now use FIRSTKEY */
        key = sv_newmortal();
        magic_nextpack(MUTABLE_SV(hv), mg, key);
        HvEITER_set(hv, NULL);     /* need to reset iterator */
        return SvOK(key) ? &PL_sv_yes : &PL_sv_no;
    }
   
    /* there is a SCALAR method that we can call */
    retval = Perl_magic_methcall(aTHX_ MUTABLE_SV(hv), mg, SV_CONST(SCALAR), 0, 0);
    if (!retval)
        retval = &PL_sv_undef;
    return retval;
}

int
Perl_magic_setdbline(pTHX_ SV *sv, MAGIC *mg)
{
    SV **svp;

    PERL_ARGS_ASSERT_MAGIC_SETDBLINE;

    /* The magic ptr/len for the debugger's hash should always be an SV.  */
    if (UNLIKELY(mg->mg_len != HEf_SVKEY)) {
        Perl_croak(aTHX_ "panic: magic_setdbline len=%" IVdf ", ptr='%s'",
                   (IV)mg->mg_len, mg->mg_ptr);
    }

    /* Use sv_2iv instead of SvIV() as the former generates smaller code, and
       setting/clearing debugger breakpoints is not a hot path.  */
    svp = av_fetch(MUTABLE_AV(mg->mg_obj),
                   sv_2iv(MUTABLE_SV((mg)->mg_ptr)), FALSE);

    if (svp && SvIOKp(*svp)) {
        OP * const o = INT2PTR(OP*,SvIVX(*svp));
        if (o) {
#ifdef PERL_DEBUG_READONLY_OPS
            Slab_to_rw(OpSLAB(o));
#endif
            /* set or clear breakpoint in the relevant control op */
            if (SvTRUE(sv))
                o->op_flags |= OPf_SPECIAL;
            else
                o->op_flags &= ~OPf_SPECIAL;
#ifdef PERL_DEBUG_READONLY_OPS
            Slab_to_ro(OpSLAB(o));
#endif
        }
    }
    return 0;
}

int
Perl_magic_getarylen(pTHX_ SV *sv, const MAGIC *mg)
{
    AV * const obj = MUTABLE_AV(mg->mg_obj);

    PERL_ARGS_ASSERT_MAGIC_GETARYLEN;

    if (obj) {
        sv_setiv(sv, AvFILL(obj));
    } else {
        sv_set_undef(sv);
    }
    return 0;
}

int
Perl_magic_setarylen(pTHX_ SV *sv, MAGIC *mg)
{
    AV * const obj = MUTABLE_AV(mg->mg_obj);

    PERL_ARGS_ASSERT_MAGIC_SETARYLEN;

    if (obj) {
        av_fill(obj, SvIV(sv));
    } else {
        Perl_ck_warner(aTHX_ packWARN(WARN_MISC),
                       "Attempt to set length of freed array");
    }
    return 0;
}

int
Perl_magic_cleararylen_p(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEARARYLEN_P;
    PERL_UNUSED_ARG(sv);
    PERL_UNUSED_CONTEXT;

    /* Reset the iterator when the array is cleared */
    if (sizeof(IV) == sizeof(SSize_t)) {
        *((IV *) &(mg->mg_len)) = 0;
    } else {
        if (mg->mg_ptr)
            *((IV *) mg->mg_ptr) = 0;
    }

    return 0;
}

int
Perl_magic_freearylen_p(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_FREEARYLEN_P;
    PERL_UNUSED_ARG(sv);

    /* during global destruction, mg_obj may already have been freed */
    if (PL_in_clean_all)
        return 0;

    mg = mg_find (mg->mg_obj, PERL_MAGIC_arylen);

    if (mg) {
        /* arylen scalar holds a pointer back to the array, but doesn't own a
           reference. Hence the we (the array) are about to go away with it
           still pointing at us. Clear its pointer, else it would be pointing
           at free memory. See the comment in sv_magic about reference loops,
           and why it can't own a reference to us.  */
        mg->mg_obj = 0;
    }
    return 0;
}

int
Perl_magic_getpos(pTHX_ SV *sv, MAGIC *mg)
{
    SV* const lsv = LvTARG(sv);
    MAGIC * const found = mg_find_mglob(lsv);

    PERL_ARGS_ASSERT_MAGIC_GETPOS;
    PERL_UNUSED_ARG(mg);

    if (found && found->mg_len != -1) {
            STRLEN i = found->mg_len;
            if (found->mg_flags & MGf_BYTES && DO_UTF8(lsv))
                i = sv_pos_b2u_flags(lsv, i, SV_GMAGIC|SV_CONST_RETURN);
            sv_setuv(sv, i);
            return 0;
    }
    sv_set_undef(sv);
    return 0;
}

int
Perl_magic_setpos(pTHX_ SV *sv, MAGIC *mg)
{
    SV* const lsv = LvTARG(sv);
    SSize_t pos;
    STRLEN len;
    MAGIC* found;
    const char *s;

    PERL_ARGS_ASSERT_MAGIC_SETPOS;
    PERL_UNUSED_ARG(mg);

    found = mg_find_mglob(lsv);
    if (!found) {
        if (!SvOK(sv))
            return 0;
        found = sv_magicext_mglob(lsv);
    }
    else if (!SvOK(sv)) {
        found->mg_len = -1;
        return 0;
    }
    s = SvPV_const(lsv, len);

    pos = SvIV(sv);

    if (DO_UTF8(lsv)) {
        const STRLEN ulen = sv_or_pv_len_utf8(lsv, s, len);
        if (ulen)
            len = ulen;
    }

    if (pos < 0) {
        pos += len;
        if (pos < 0)
            pos = 0;
    }
    else if (pos > (SSize_t)len)
        pos = len;

    found->mg_len = pos;
    found->mg_flags &= ~(MGf_MINMATCH|MGf_BYTES);

    return 0;
}

int
Perl_magic_getsubstr(pTHX_ SV *sv, MAGIC *mg)
{
    STRLEN len;
    SV * const lsv = LvTARG(sv);
    const char * const tmps = SvPV_const(lsv,len);
    STRLEN offs = LvTARGOFF(sv);
    STRLEN rem = LvTARGLEN(sv);
    const bool negoff = LvFLAGS(sv) & LVf_NEG_OFF;
    const bool negrem = LvFLAGS(sv) & LVf_NEG_LEN;

    PERL_ARGS_ASSERT_MAGIC_GETSUBSTR;
    PERL_UNUSED_ARG(mg);

    if (!translate_substr_offsets(
            SvUTF8(lsv) ? sv_or_pv_len_utf8(lsv, tmps, len) : len,
            negoff ? -(IV)offs : (IV)offs, !negoff,
            negrem ? -(IV)rem  : (IV)rem,  !negrem, &offs, &rem
    )) {
        Perl_ck_warner(aTHX_ packWARN(WARN_SUBSTR), "substr outside of string");
        sv_set_undef(sv);
        return 0;
    }

    if (SvUTF8(lsv))
        offs = sv_or_pv_pos_u2b(lsv, tmps, offs, &rem);
    sv_setpvn(sv, tmps + offs, rem);
    if (SvUTF8(lsv))
        SvUTF8_on(sv);
    return 0;
}

int
Perl_magic_setsubstr(pTHX_ SV *sv, MAGIC *mg)
{
    STRLEN len, lsv_len, oldtarglen, newtarglen;
    const char * const tmps = SvPV_const(sv, len);
    SV * const lsv = LvTARG(sv);
    STRLEN lvoff = LvTARGOFF(sv);
    STRLEN lvlen = LvTARGLEN(sv);
    const bool negoff = LvFLAGS(sv) & LVf_NEG_OFF;
    const bool neglen = LvFLAGS(sv) & LVf_NEG_LEN;

    PERL_ARGS_ASSERT_MAGIC_SETSUBSTR;
    PERL_UNUSED_ARG(mg);

    SvGETMAGIC(lsv);
    if (SvROK(lsv))
        Perl_ck_warner(aTHX_ packWARN(WARN_SUBSTR),
                            "Attempt to use reference as lvalue in substr"
        );
    SvPV_force_nomg(lsv,lsv_len);
    if (SvUTF8(lsv)) lsv_len = sv_len_utf8_nomg(lsv);
    if (!translate_substr_offsets(
            lsv_len,
            negoff ? -(IV)lvoff : (IV)lvoff, !negoff,
            neglen ? -(IV)lvlen : (IV)lvlen, !neglen, &lvoff, &lvlen
    ))
        Perl_croak(aTHX_ "substr outside of string");
    oldtarglen = lvlen;
    if (DO_UTF8(sv)) {
        sv_utf8_upgrade_nomg(lsv);
        lvoff = sv_pos_u2b_flags(lsv, lvoff, &lvlen, SV_CONST_RETURN);
        sv_insert_flags(lsv, lvoff, lvlen, tmps, len, 0);
        newtarglen = sv_or_pv_len_utf8(sv, tmps, len);
        SvUTF8_on(lsv);
    }
    else if (SvUTF8(lsv)) {
        const char *utf8;
        lvoff = sv_pos_u2b_flags(lsv, lvoff, &lvlen, SV_CONST_RETURN);
        newtarglen = len;
        utf8 = (char*)bytes_to_utf8((U8*)tmps, &len);
        sv_insert_flags(lsv, lvoff, lvlen, utf8, len, 0);
        Safefree(utf8);
    }
    else {
        sv_insert_flags(lsv, lvoff, lvlen, tmps, len, 0);
        newtarglen = len;
    }
    if (!neglen) LvTARGLEN(sv) = newtarglen;
    if (negoff)  LvTARGOFF(sv) += newtarglen - oldtarglen;

    return 0;
}

int
Perl_magic_gettaint(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_GETTAINT;
    PERL_UNUSED_ARG(sv);
#ifdef NO_TAINT_SUPPORT
    PERL_UNUSED_ARG(mg);
#endif

    TAINT_IF((PL_localizing != 1) && (mg->mg_len & 1) && IN_PERL_RUNTIME);
    return 0;
}

int
Perl_magic_settaint(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETTAINT;
    PERL_UNUSED_ARG(sv);

    /* update taint status */
    if (TAINT_get)
        mg->mg_len |= 1;
    else
        mg->mg_len &= ~1;
    return 0;
}

int
Perl_magic_getvec(pTHX_ SV *sv, MAGIC *mg)
{
    SV * const lsv = LvTARG(sv);
    char errflags = LvFLAGS(sv);

    PERL_ARGS_ASSERT_MAGIC_GETVEC;
    PERL_UNUSED_ARG(mg);

    /* non-zero errflags implies deferred out-of-range condition */
    assert(!(errflags & ~(LVf_NEG_OFF|LVf_OUT_OF_RANGE)));
    sv_setuv(sv, errflags ? 0 : do_vecget(lsv, LvTARGOFF(sv), LvTARGLEN(sv)));

    return 0;
}

int
Perl_magic_setvec(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETVEC;
    PERL_UNUSED_ARG(mg);
    do_vecset(sv);	/* XXX slurp this routine */
    return 0;
}

SV *
Perl_defelem_target(pTHX_ SV *sv, MAGIC *mg)
{
    SV *targ = NULL;
    PERL_ARGS_ASSERT_DEFELEM_TARGET;
    if (!mg) mg = mg_find(sv, PERL_MAGIC_defelem);
    assert(mg);
    if (LvTARGLEN(sv)) {
        if (mg->mg_obj) {
            SV * const ahv = LvTARG(sv);
            HE * const he = hv_fetch_ent(MUTABLE_HV(ahv), mg->mg_obj, FALSE, 0);
            if (he)
                targ = HeVAL(he);
        }
        else if (LvSTARGOFF(sv) >= 0) {
            AV *const av = MUTABLE_AV(LvTARG(sv));
            if (LvSTARGOFF(sv) <= AvFILL(av))
            {
              if (SvRMAGICAL(av)) {
                SV * const * const svp = av_fetch(av, LvSTARGOFF(sv), 0);
                targ = svp ? *svp : NULL;
              }
              else
                targ = AvARRAY(av)[LvSTARGOFF(sv)];
            }
        }
        if (targ && (targ != &PL_sv_undef)) {
            /* somebody else defined it for us */
            SvREFCNT_dec(LvTARG(sv));
            LvTARG(sv) = SvREFCNT_inc_simple_NN(targ);
            LvTARGLEN(sv) = 0;
            SvREFCNT_dec(mg->mg_obj);
            mg->mg_obj = NULL;
            mg->mg_flags &= ~MGf_REFCOUNTED;
        }
        return targ;
    }
    else
        return LvTARG(sv);
}

int
Perl_magic_getdefelem(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_GETDEFELEM;

    sv_setsv(sv, defelem_target(sv, mg));
    return 0;
}

int
Perl_magic_setdefelem(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETDEFELEM;
    PERL_UNUSED_ARG(mg);
    if (LvTARGLEN(sv))
        vivify_defelem(sv);
    if (LvTARG(sv)) {
        sv_setsv(LvTARG(sv), sv);
        SvSETMAGIC(LvTARG(sv));
    }
    return 0;
}

void
Perl_vivify_defelem(pTHX_ SV *sv)
{
    MAGIC *mg;
    SV *value = NULL;

    PERL_ARGS_ASSERT_VIVIFY_DEFELEM;

    if (!LvTARGLEN(sv) || !(mg = mg_find(sv, PERL_MAGIC_defelem)))
        return;
    if (mg->mg_obj) {
        SV * const ahv = LvTARG(sv);
        HE * const he = hv_fetch_ent(MUTABLE_HV(ahv), mg->mg_obj, TRUE, 0);
        if (he)
            value = HeVAL(he);
        if (!value || value == &PL_sv_undef)
            Perl_croak(aTHX_ PL_no_helem_sv, SVfARG(mg->mg_obj));
    }
    else if (LvSTARGOFF(sv) < 0)
        Perl_croak(aTHX_ PL_no_aelem, LvSTARGOFF(sv));
    else {
        AV *const av = MUTABLE_AV(LvTARG(sv));
        if ((I32)LvTARGLEN(sv) < 0 && LvSTARGOFF(sv) > AvFILL(av))
            LvTARG(sv) = NULL;	/* array can't be extended */
        else {
            SV* const * const svp = av_fetch(av, LvSTARGOFF(sv), TRUE);
            if (!svp || !(value = *svp))
                Perl_croak(aTHX_ PL_no_aelem, LvSTARGOFF(sv));
        }
    }
    SvREFCNT_inc_simple_void(value);
    SvREFCNT_dec(LvTARG(sv));
    LvTARG(sv) = value;
    LvTARGLEN(sv) = 0;
    SvREFCNT_dec(mg->mg_obj);
    mg->mg_obj = NULL;
    mg->mg_flags &= ~MGf_REFCOUNTED;
}

int
Perl_magic_setnonelem(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETNONELEM;
    PERL_UNUSED_ARG(mg);
    sv_unmagic(sv, PERL_MAGIC_nonelem);
    return 0;
}

int
Perl_magic_killbackrefs(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_KILLBACKREFS;
    Perl_sv_kill_backrefs(aTHX_ sv, MUTABLE_AV(mg->mg_obj));
    return 0;
}

int
Perl_magic_setmglob(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETMGLOB;
    PERL_UNUSED_CONTEXT;
    PERL_UNUSED_ARG(sv);
    mg->mg_len = -1;
    return 0;
}


int
Perl_magic_freemglob(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_FREEMGLOB;
    PERL_UNUSED_ARG(sv);

    /* pos() magic uses mg_len as a string position rather than a buffer
     * length, and mg_ptr is currently unused, so skip freeing.
     */
    assert(mg->mg_type == PERL_MAGIC_regex_global && mg->mg_len >= -1);
    mg->mg_ptr = NULL;
    return 0;
}


int
Perl_magic_setuvar(pTHX_ SV *sv, MAGIC *mg)
{
    const struct ufuncs * const uf = (struct ufuncs *)mg->mg_ptr;

    PERL_ARGS_ASSERT_MAGIC_SETUVAR;

    if (uf && uf->uf_set)
        (*uf->uf_set)(aTHX_ uf->uf_index, sv);
    return 0;
}

int
Perl_magic_setregexp(pTHX_ SV *sv, MAGIC *mg)
{
    const char type = mg->mg_type;

    PERL_ARGS_ASSERT_MAGIC_SETREGEXP;

    assert(    type == PERL_MAGIC_fm
            || type == PERL_MAGIC_qr
            || type == PERL_MAGIC_bm);
    return sv_unmagic(sv, type);
}

#ifdef USE_LOCALE_COLLATE
int
Perl_magic_setcollxfrm(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETCOLLXFRM;

    /*
     * RenE<eacute> Descartes said "I think not."
     * and vanished with a faint plop.
     */
    PERL_UNUSED_CONTEXT;
    PERL_UNUSED_ARG(sv);
    if (mg->mg_ptr) {
        Safefree(mg->mg_ptr);
        mg->mg_ptr = NULL;
        mg->mg_len = -1;
    }
    return 0;
}

int
Perl_magic_freecollxfrm(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_FREECOLLXFRM;
    PERL_UNUSED_ARG(sv);

    /* Collate magic uses mg_len as a string length rather than a buffer
     * length, so we need to free even with mg_len == 0: hence we can't
     * rely on standard magic free handling */
    if (mg->mg_len >= 0) {
        assert(mg->mg_type == PERL_MAGIC_collxfrm);
        Safefree(mg->mg_ptr);
        mg->mg_ptr = NULL;
    }

    return 0;
}
#endif /* USE_LOCALE_COLLATE */

/* Just clear the UTF-8 cache data. */
int
Perl_magic_setutf8(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_SETUTF8;
    PERL_UNUSED_CONTEXT;
    PERL_UNUSED_ARG(sv);
    Safefree(mg->mg_ptr);	/* The mg_ptr holds the pos cache. */
    mg->mg_ptr = NULL;
    mg->mg_len = -1;		/* The mg_len holds the len cache. */
    return 0;
}

int
Perl_magic_freeutf8(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_FREEUTF8;
    PERL_UNUSED_ARG(sv);

    /* utf8 magic uses mg_len as a string length rather than a buffer
     * length, so we need to free even with mg_len == 0: hence we can't
     * rely on standard magic free handling */
    assert(mg->mg_type == PERL_MAGIC_utf8 && mg->mg_len >= -1);
    Safefree(mg->mg_ptr);
    mg->mg_ptr = NULL;
    return 0;
}


int
Perl_magic_setlvref(pTHX_ SV *sv, MAGIC *mg)
{
    const char *bad = NULL;
    PERL_ARGS_ASSERT_MAGIC_SETLVREF;
    if (!SvROK(sv)) Perl_croak(aTHX_ "Assigned value is not a reference");
    switch (mg->mg_private & OPpLVREF_TYPE) {
    case OPpLVREF_SV:
        if (SvTYPE(SvRV(sv)) > SVt_PVLV)
            bad = " SCALAR";
        break;
    case OPpLVREF_AV:
        if (SvTYPE(SvRV(sv)) != SVt_PVAV)
            bad = "n ARRAY";
        break;
    case OPpLVREF_HV:
        if (SvTYPE(SvRV(sv)) != SVt_PVHV)
            bad = " HASH";
        break;
    case OPpLVREF_CV:
        if (SvTYPE(SvRV(sv)) != SVt_PVCV)
            bad = " CODE";
    }
    if (bad)
        /* diag_listed_as: Assigned value is not %s reference */
        Perl_croak(aTHX_ "Assigned value is not a%s reference", bad);
    switch (mg->mg_obj ? SvTYPE(mg->mg_obj) : 0) {
    case 0:
    {
        SV * const old = PAD_SV(mg->mg_len);
        PAD_SETSV(mg->mg_len, SvREFCNT_inc_NN(SvRV(sv)));
        SvREFCNT_dec(old);
        break;
    }
    case SVt_PVGV:
        gv_setref(mg->mg_obj, sv);
        SvSETMAGIC(mg->mg_obj);
        break;
    case SVt_PVAV:
        av_store((AV *)mg->mg_obj, SvIV((SV *)mg->mg_ptr),
                 SvREFCNT_inc_simple_NN(SvRV(sv)));
        break;
    case SVt_PVHV:
        (void)hv_store_ent((HV *)mg->mg_obj, (SV *)mg->mg_ptr,
                           SvREFCNT_inc_simple_NN(SvRV(sv)), 0);
    }
    if (mg->mg_flags & MGf_PERSIST)
        NOOP; /* This sv is in use as an iterator var and will be reused,
                 so we must leave the magic.  */
    else
        /* This sv could be returned by the assignment op, so clear the
           magic, as lvrefs are an implementation detail that must not be
           leaked to the user.  */
        sv_unmagic(sv, PERL_MAGIC_lvref);
    return 0;
}

static void
S_set_dollarzero(pTHX_ SV *sv)
    PERL_TSA_REQUIRES(PL_dollarzero_mutex)
{
    const char *s;
    STRLEN len;
#ifdef HAS_SETPROCTITLE
    /* The BSDs don't show the argv[] in ps(1) output, they
     * show a string from the process struct and provide
     * the setproctitle() routine to manipulate that. */
    if (PL_origalen != 1) {
        s = SvPV_const(sv, len);
#   if __FreeBSD_version > 410001 || defined(__DragonFly__)
        /* The leading "-" removes the "perl: " prefix,
         * but not the "(perl) suffix from the ps(1)
         * output, because that's what ps(1) shows if the
         * argv[] is modified. */
        setproctitle("-%s", s);
#   else	/* old FreeBSDs, NetBSD, OpenBSD, anyBSD */
        /* This doesn't really work if you assume that
         * $0 = 'foobar'; will wipe out 'perl' from the $0
         * because in ps(1) output the result will be like
         * sprintf("perl: %s (perl)", s)
         * I guess this is a security feature:
         * one (a user process) cannot get rid of the original name.
         * --jhi */
        setproctitle("%s", s);
#   endif
    }
#elif defined(__hpux) && defined(PSTAT_SETCMD)
    if (PL_origalen != 1) {
        union pstun un;
        s = SvPV_const(sv, len);
        un.pst_command = (char *)s;
        pstat(PSTAT_SETCMD, un, len, 0, 0);
    }
#else
    if (PL_origalen > 1) {
        I32 i;
        /* PL_origalen is set in perl_parse(). */
        s = SvPV_force(sv,len);
        if (len >= (STRLEN)PL_origalen-1) {
            /* Longer than original, will be truncated. We assume that
             * PL_origalen bytes are available. */
            Copy(s, PL_origargv[0], PL_origalen-1, char);
        }
        else {
            /* Shorter than original, will be padded. */
#ifdef PERL_DARWIN
            /* Special case for Mac OS X: see [perl #38868] */
            const int pad = 0;
#else
            /* Is the space counterintuitive?  Yes.
             * (You were expecting \0?)
             * Does it work?  Seems to.  (In Linux 2.4.20 at least.)
             * --jhi */
            const int pad = ' ';
#endif
            Copy(s, PL_origargv[0], len, char);
            PL_origargv[0][len] = 0;
            memset(PL_origargv[0] + len + 1,
                   pad,  PL_origalen - len - 1);
        }
        PL_origargv[0][PL_origalen-1] = 0;
        for (i = 1; i < PL_origargc; i++)
            PL_origargv[i] = 0;
#ifdef HAS_PRCTL_SET_NAME
        /* Set the legacy process name in addition to the POSIX name on Linux */
        if (prctl(PR_SET_NAME, (unsigned long)s, 0, 0, 0) != 0) {
            /* diag_listed_as: SKIPME */
            Perl_croak(aTHX_ "Can't set $0 with prctl(): %s", Strerror(errno));
        }
#endif
    }
#endif
}

int
Perl_magic_set(pTHX_ SV *sv, MAGIC *mg)
{
    I32 paren;
    const REGEXP * rx;
    I32 i;
    STRLEN len;
    MAGIC *tmg;

    PERL_ARGS_ASSERT_MAGIC_SET;

    if (!mg->mg_ptr) {
        paren = mg->mg_len;
        if (PL_curpm && (rx = PM_GETRE(PL_curpm))) {
          setparen_got_rx:
            CALLREG_NUMBUF_STORE((REGEXP *)rx,paren,sv);
        } else {
            /* Croak with a READONLY error when a numbered match var is
             * set without a previous pattern match. Unless it's C<local $1>
             */
          croakparen:
            if (!PL_localizing) {
                Perl_croak_no_modify();
            }
        }
        return 0;
    }

    switch (*mg->mg_ptr) {
    case '\001':	/* ^A */
        if (SvOK(sv)) sv_copypv(PL_bodytarget, sv);
        else SvOK_off(PL_bodytarget);
        FmLINES(PL_bodytarget) = 0;
        if (SvPOK(PL_bodytarget)) {
            char *s = SvPVX(PL_bodytarget);
            char *e = SvEND(PL_bodytarget);
            while ( ((s = (char *) memchr(s, '\n', e - s))) ) {
                FmLINES(PL_bodytarget)++;
                s++;
            }
        }
        /* mg_set() has temporarily made sv non-magical */
        if (TAINTING_get) {
            if ((tmg = mg_find(sv,PERL_MAGIC_taint)) && tmg->mg_len & 1)
                SvTAINTED_on(PL_bodytarget);
            else
                SvTAINTED_off(PL_bodytarget);
        }
        break;
    case '\003':	/* ^C */
        PL_minus_c = cBOOL(SvIV(sv));
        break;

    case '\004':	/* ^D */
#ifdef DEBUGGING
        {
            const char *s = SvPV_nolen_const(sv);
            PL_debug = get_debug_opts(&s, 0) | DEBUG_TOP_FLAG;
            if (DEBUG_x_TEST || DEBUG_B_TEST)
                dump_all_perl(!DEBUG_B_TEST);
        }
#else
        PL_debug = (SvIV(sv)) | DEBUG_TOP_FLAG;
#endif
        break;
    case '\005':  /* ^E */
        if (*(mg->mg_ptr+1) == '\0') {
#ifdef VMS
            set_vaxc_errno(SvIV(sv));
#elif defined(WIN32)
            SetLastError( SvIV(sv) );
#elif defined(OS2)
            os2_setsyserrno(SvIV(sv));
#else
            /* will anyone ever use this? */
            SETERRNO(SvIV(sv), 4);
#endif
        }
        else if (strEQ(mg->mg_ptr + 1, "NCODING") && SvOK(sv))
            Perl_croak(aTHX_ "${^ENCODING} is no longer supported");
        break;
    case '\006':	/* ^F */
        if (mg->mg_ptr[1] == '\0') {
            PL_maxsysfd = SvIV(sv);
        }
        break;
    case '\010':	/* ^H */
        {
            U32 save_hints = PL_hints;
            PL_hints = SvUV(sv);

            /* If wasn't UTF-8, and now is, notify the parser */
            if ((PL_hints & HINT_UTF8) && ! (save_hints & HINT_UTF8)) {
                notify_parser_that_changed_to_utf8();
            }
        }
        break;
    case '\011':	/* ^I */ /* NOT \t in EBCDIC */
        Safefree(PL_inplace);
        PL_inplace = SvOK(sv) ? savesvpv(sv) : NULL;
        break;
    case '\016':	/* ^N */
        if (PL_curpm && (rx = PM_GETRE(PL_curpm))
         && (paren = RX_LASTCLOSEPAREN(rx))) goto setparen_got_rx;
        goto croakparen;
    case '\017':	/* ^O */
        if (*(mg->mg_ptr+1) == '\0') {
            Safefree(PL_osname);
            PL_osname = NULL;
            if (SvOK(sv)) {
                TAINT_PROPER("assigning to $^O");
                PL_osname = savesvpv(sv);
            }
        }
        else if (strEQ(mg->mg_ptr, "\017PEN")) {
            STRLEN len;
            const char *const start = SvPV(sv, len);
            const char *out = (const char*)memchr(start, '\0', len);
            SV *tmp;


            PL_compiling.cop_hints |= HINT_LEXICAL_IO_IN | HINT_LEXICAL_IO_OUT;
            PL_hints |= HINT_LEXICAL_IO_IN | HINT_LEXICAL_IO_OUT;

            /* Opening for input is more common than opening for output, so
               ensure that hints for input are sooner on linked list.  */
            tmp = out ? newSVpvn_flags(out + 1, start + len - out - 1,
                                       SvUTF8(sv))
                : newSVpvs_flags("", SvUTF8(sv));
            (void)hv_stores(GvHV(PL_hintgv), "open>", tmp);
            mg_set(tmp);

            tmp = newSVpvn_flags(start, out ? (STRLEN)(out - start) : len,
                                        SvUTF8(sv));
            (void)hv_stores(GvHV(PL_hintgv), "open<", tmp);
            mg_set(tmp);
        }
        break;
    case '\020':	/* ^P */
          PL_perldb = SvIV(sv);
          if (PL_perldb && !PL_DBsingle)
              init_debugger();
      break;
    case '\024':	/* ^T */
#ifdef BIG_TIME
        PL_basetime = (Time_t)(SvNOK(sv) ? SvNVX(sv) : sv_2nv(sv));
#else
        PL_basetime = (Time_t)SvIV(sv);
#endif
        break;
    case '\025':	/* ^UTF8CACHE */
         if (strEQ(mg->mg_ptr+1, "TF8CACHE")) {
             PL_utf8cache = (signed char) sv_2iv(sv);
         }
         break;
    case '\027':	/* ^W & $^WARNING_BITS */
        if (*(mg->mg_ptr+1) == '\0') {
            if ( ! (PL_dowarn & G_WARN_ALL_MASK)) {
                i = SvIV(sv);
                PL_dowarn = (PL_dowarn & ~G_WARN_ON)
                                | (i ? G_WARN_ON : G_WARN_OFF) ;
            }
        }
        else if (strEQ(mg->mg_ptr+1, "ARNING_BITS")) {
            if ( ! (PL_dowarn & G_WARN_ALL_MASK)) {
                if (!SvPOK(sv)) {
            free_and_set_cop_warnings(&PL_compiling, pWARN_STD);
                    break;
                }
                {
                    STRLEN len, i;
                    int not_none = 0, not_all = 0;
                    const U8 * const ptr = (const U8 *)SvPV_const(sv, len) ;
                    for (i = 0 ; i < len ; ++i) {
                        not_none |= ptr[i];
                        not_all |= ptr[i] ^ 0x55;
                    }
                    if (!not_none) {
                free_and_set_cop_warnings(&PL_compiling, pWARN_NONE);
                    } else if (len >= WARNsize && !not_all) {
                free_and_set_cop_warnings(&PL_compiling, pWARN_ALL);
                    PL_dowarn |= G_WARN_ONCE ;
                }
            else {
                             STRLEN len;
                             const char *const p = SvPV_const(sv, len);

                             PL_compiling.cop_warnings
                                 = Perl_new_warnings_bitfield(aTHX_ PL_compiling.cop_warnings,
                                                         p, len);

                     if (isWARN_on(PL_compiling.cop_warnings, WARN_ONCE))
                            PL_dowarn |= G_WARN_ONCE ;
               }

                }
            }
        }
        break;
    case '.':
        if (PL_localizing) {
            if (PL_localizing == 1)
                SAVESPTR(PL_last_in_gv);
        }
        else if (SvOK(sv) && GvIO(PL_last_in_gv))
            IoLINES(GvIOp(PL_last_in_gv)) = SvIV(sv);
        break;
    case '^':
        Safefree(IoTOP_NAME(GvIOp(PL_defoutgv)));
        IoTOP_NAME(GvIOp(PL_defoutgv)) = savesvpv(sv);
        IoTOP_GV(GvIOp(PL_defoutgv)) =  gv_fetchsv(sv, GV_ADD, SVt_PVIO);
        break;
    case '~':
        Safefree(IoFMT_NAME(GvIOp(PL_defoutgv)));
        IoFMT_NAME(GvIOp(PL_defoutgv)) = savesvpv(sv);
        IoFMT_GV(GvIOp(PL_defoutgv)) =  gv_fetchsv(sv, GV_ADD, SVt_PVIO);
        break;
    case '=':
        IoPAGE_LEN(GvIOp(PL_defoutgv)) = (SvIV(sv));
        break;
    case '-':
        IoLINES_LEFT(GvIOp(PL_defoutgv)) = (SvIV(sv));
        if (IoLINES_LEFT(GvIOp(PL_defoutgv)) < 0L)
                IoLINES_LEFT(GvIOp(PL_defoutgv)) = 0L;
        break;
    case '%':
        IoPAGE(GvIOp(PL_defoutgv)) = (SvIV(sv));
        break;
    case '|':
        {
            IO * const io = GvIO(PL_defoutgv);
            if(!io)
              break;
            if ((SvIV(sv)) == 0)
                IoFLAGS(io) &= ~IOf_FLUSH;
            else {
                if (!(IoFLAGS(io) & IOf_FLUSH)) {
                    PerlIO *ofp = IoOFP(io);
                    if (ofp)
                        (void)PerlIO_flush(ofp);
                    IoFLAGS(io) |= IOf_FLUSH;
                }
            }
        }
        break;
    case '/':
        {
            if (SvROK(sv)) {
                SV *referent = SvRV(sv);
                const char *reftype = sv_reftype(referent, 0);
                /* XXX: dodgy type check: This leaves me feeling dirty, but
                 * the alternative is to copy pretty much the entire
                 * sv_reftype() into this routine, or to do a full string
                 * comparison on the return of sv_reftype() both of which
                 * make me feel worse! NOTE, do not modify this comment
                 * without reviewing the corresponding comment in
                 * sv_reftype(). - Yves */
                if (reftype[0] == 'S' || reftype[0] == 'L') {
                    IV val = SvIV(referent);
                    if (val <= 0) {
                        sv_setsv(sv, PL_rs);
                        Perl_croak(aTHX_ "Setting $/ to a reference to %s is forbidden",
                                         val < 0 ? "a negative integer" : "zero");
                    }
                } else {
                    sv_setsv(sv, PL_rs);
                    /* diag_listed_as: Setting $/ to %s reference is forbidden */
                    Perl_croak(aTHX_ "Setting $/ to a%s %s reference is forbidden",
                                      *reftype == 'A' ? "n" : "", reftype);
                }
            }
            SvREFCNT_dec(PL_rs);
            PL_rs = newSVsv(sv);
        }
        break;
    case '\\':
        SvREFCNT_dec(PL_ors_sv);
        if (SvOK(sv)) {
            PL_ors_sv = newSVsv(sv);
        }
        else {
            PL_ors_sv = NULL;
        }
        break;
    case '[':
        if (SvIV(sv) != 0)
            Perl_croak(aTHX_ "Assigning non-zero to $[ is no longer possible");
        break;
    case '?':
#ifdef COMPLEX_STATUS
        if (PL_localizing == 2) {
            SvUPGRADE(sv, SVt_PVLV);
            PL_statusvalue = LvTARGOFF(sv);
            PL_statusvalue_vms = LvTARGLEN(sv);
        }
        else
#endif
#ifdef VMSISH_STATUS
        if (VMSISH_STATUS)
            STATUS_NATIVE_CHILD_SET((U32)SvIV(sv));
        else
#endif
            STATUS_UNIX_EXIT_SET(SvIV(sv));
        break;
    case '!':
        {
#ifdef VMS
#   define PERL_VMS_BANG vaxc$errno
#else
#   define PERL_VMS_BANG 0
#endif
#if defined(WIN32)
        SETERRNO(win32_get_errno(SvIOK(sv) ? SvIVX(sv) : SvOK(sv) ? sv_2iv(sv) : 0),
                 (SvIV(sv) == EVMSERR) ? 4 : PERL_VMS_BANG);
#else
        SETERRNO(SvIOK(sv) ? SvIVX(sv) : SvOK(sv) ? sv_2iv(sv) : 0,
                 (SvIV(sv) == EVMSERR) ? 4 : PERL_VMS_BANG);
#endif
        }
        break;
    case '<':
        {
        /* XXX $< currently silently ignores failures */
        const Uid_t new_uid = SvUID(sv);
        PL_delaymagic_uid = new_uid;
        if (PL_delaymagic) {
            PL_delaymagic |= DM_RUID;
            break;				/* don't do magic till later */
        }
#ifdef HAS_SETRUID
        PERL_UNUSED_RESULT(setruid(new_uid));
#elif defined(HAS_SETREUID)
        PERL_UNUSED_RESULT(setreuid(new_uid, (Uid_t)-1));
#elif defined(HAS_SETRESUID)
        PERL_UNUSED_RESULT(setresuid(new_uid, (Uid_t)-1, (Uid_t)-1));
#else
        if (new_uid == PerlProc_geteuid()) {		/* special case $< = $> */
#  ifdef PERL_DARWIN
            /* workaround for Darwin's setuid peculiarity, cf [perl #24122] */
            if (new_uid != 0 && PerlProc_getuid() == 0)
                PERL_UNUSED_RESULT(PerlProc_setuid(0));
#  endif
            PERL_UNUSED_RESULT(PerlProc_setuid(new_uid));
        } else {
            Perl_croak(aTHX_ "setruid() not implemented");
        }
#endif
        break;
        }
    case '>':
        {
        /* XXX $> currently silently ignores failures */
        const Uid_t new_euid = SvUID(sv);
        PL_delaymagic_euid = new_euid;
        if (PL_delaymagic) {
            PL_delaymagic |= DM_EUID;
            break;				/* don't do magic till later */
        }
#ifdef HAS_SETEUID
        PERL_UNUSED_RESULT(seteuid(new_euid));
#elif defined(HAS_SETREUID)
        PERL_UNUSED_RESULT(setreuid((Uid_t)-1, new_euid));
#elif defined(HAS_SETRESUID)
        PERL_UNUSED_RESULT(setresuid((Uid_t)-1, new_euid, (Uid_t)-1));
#else
        if (new_euid == PerlProc_getuid())		/* special case $> = $< */
            PERL_UNUSED_RESULT(PerlProc_setuid(new_euid));
        else {
            Perl_croak(aTHX_ "seteuid() not implemented");
        }
#endif
        break;
        }
    case '(':
        {
        /* XXX $( currently silently ignores failures */
        const Gid_t new_gid = SvGID(sv);
        PL_delaymagic_gid = new_gid;
        if (PL_delaymagic) {
            PL_delaymagic |= DM_RGID;
            break;				/* don't do magic till later */
        }
#ifdef HAS_SETRGID
        PERL_UNUSED_RESULT(setrgid(new_gid));
#elif defined(HAS_SETREGID)
        PERL_UNUSED_RESULT(setregid(new_gid, (Gid_t)-1));
#elif defined(HAS_SETRESGID)
        PERL_UNUSED_RESULT(setresgid(new_gid, (Gid_t)-1, (Gid_t) -1));
#else
        if (new_gid == PerlProc_getegid())			/* special case $( = $) */
            PERL_UNUSED_RESULT(PerlProc_setgid(new_gid));
        else {
            Perl_croak(aTHX_ "setrgid() not implemented");
        }
#endif
        break;
        }
    case ')':
        {
/* (hv) best guess: maybe we'll need configure probes to do a better job,
 * but you can override it if you need to.
 */
#ifndef INVALID_GID
#define INVALID_GID ((Gid_t)-1)
#endif
        /* XXX $) currently silently ignores failures */
        Gid_t new_egid;
#ifdef HAS_SETGROUPS
        {
            const char *p = SvPV_const(sv, len);
            Groups_t *gary = NULL;
            const char* p_end = p + len;
            const char* endptr = p_end;
            UV uv;
#ifdef _SC_NGROUPS_MAX
           int maxgrp = sysconf(_SC_NGROUPS_MAX);

           if (maxgrp < 0)
               maxgrp = NGROUPS;
#else
           int maxgrp = NGROUPS;
#endif

            while (isSPACE(*p))
                ++p;
            if (grok_atoUV(p, &uv, &endptr))
                new_egid = (Gid_t)uv;
            else {
                new_egid = INVALID_GID;
                endptr = NULL;
            }
            for (i = 0; i < maxgrp; ++i) {
                if (endptr == NULL)
                    break;
                p = endptr;
                endptr = p_end;
                while (isSPACE(*p))
                    ++p;
                if (!*p)
                    break;
                if (!gary)
                    Newx(gary, i + 1, Groups_t);
                else
                    Renew(gary, i + 1, Groups_t);
                if (grok_atoUV(p, &uv, &endptr))
                    gary[i] = (Groups_t)uv;
                else {
                    gary[i] = INVALID_GID;
                    endptr = NULL;
                }
            }
            if (i)
                PERL_UNUSED_RESULT(setgroups(i, gary));
            Safefree(gary);
        }
#else  /* HAS_SETGROUPS */
        new_egid = SvGID(sv);
#endif /* HAS_SETGROUPS */
        PL_delaymagic_egid = new_egid;
        if (PL_delaymagic) {
            PL_delaymagic |= DM_EGID;
            break;				/* don't do magic till later */
        }
#ifdef HAS_SETEGID
        PERL_UNUSED_RESULT(setegid(new_egid));
#elif defined(HAS_SETREGID)
        PERL_UNUSED_RESULT(setregid((Gid_t)-1, new_egid));
#elif defined(HAS_SETRESGID)
        PERL_UNUSED_RESULT(setresgid((Gid_t)-1, new_egid, (Gid_t)-1));
#else
        if (new_egid == PerlProc_getgid())			/* special case $) = $( */
            PERL_UNUSED_RESULT(PerlProc_setgid(new_egid));
        else {
            Perl_croak(aTHX_ "setegid() not implemented");
        }
#endif
        break;
        }
    case ':':
        PL_chopset = SvPV_force(sv,len);
        break;
    case '$': /* $$ */
        /* Store the pid in mg->mg_obj so we can tell when a fork has
           occurred.  mg->mg_obj points to *$ by default, so clear it. */
        if (isGV(mg->mg_obj)) {
            if (mg->mg_flags & MGf_REFCOUNTED) /* probably never true */
                SvREFCNT_dec(mg->mg_obj);
            mg->mg_flags |= MGf_REFCOUNTED;
            mg->mg_obj = newSViv((IV)PerlProc_getpid());
        }
        else sv_setiv(mg->mg_obj, (IV)PerlProc_getpid());
        break;
    case '0':
        if (!sv_utf8_downgrade(sv, /* fail_ok */ TRUE)) {

            /* Since we are going to set the string's UTF8-encoded form
               as the process name we should update $0 itself to contain
               that same (UTF8-encoded) value. */
            sv_utf8_encode(GvSV(mg->mg_obj));

            Perl_ck_warner_d(aTHX_ packWARN(WARN_UTF8), "Wide character in %s", "$0");
        }

        LOCK_DOLLARZERO_MUTEX;
        S_set_dollarzero(aTHX_ sv);
        UNLOCK_DOLLARZERO_MUTEX;
        break;
    }
    return 0;
}

/*
=for apidoc_section $signals
=for apidoc whichsig
=for apidoc_item whichsig_pv
=for apidoc_item whichsig_pvn
=for apidoc_item whichsig_sv

These all convert a signal name into its corresponding signal number;
returning -1 if no corresponding number was found.

They differ only in the source of the signal name:

C<whichsig_pv> takes the name from the C<NUL>-terminated string starting at
C<sig>.

C<whichsig> is merely a different spelling, a synonym, of C<whichsig_pv>.

C<whichsig_pvn> takes the name from the string starting at C<sig>, with length
C<len> bytes.

C<whichsig_sv> takes the name from the PV stored in the SV C<sigsv>.

=cut
*/

I32
Perl_whichsig_sv(pTHX_ SV *sigsv)
{
    const char *sigpv;
    STRLEN siglen;
    PERL_ARGS_ASSERT_WHICHSIG_SV;
    sigpv = SvPV_const(sigsv, siglen);
    return whichsig_pvn(sigpv, siglen);
}

I32
Perl_whichsig_pv(pTHX_ const char *sig)
{
    PERL_ARGS_ASSERT_WHICHSIG_PV;
    return whichsig_pvn(sig, strlen(sig));
}

I32
Perl_whichsig_pvn(pTHX_ const char *sig, STRLEN len)
{
    char* const* sigv;

    PERL_ARGS_ASSERT_WHICHSIG_PVN;
    PERL_UNUSED_CONTEXT;

    for (sigv = (char* const*)PL_sig_name; *sigv; sigv++)
        if (strlen(*sigv) == len && memEQ(sig,*sigv, len))
            return PL_sig_num[sigv - (char* const*)PL_sig_name];
#ifdef SIGCLD
    if (memEQs(sig, len, "CHLD"))
        return SIGCLD;
#endif
#ifdef SIGCHLD
    if (memEQs(sig, len, "CLD"))
        return SIGCHLD;
#endif
    return -1;
}


/* Perl_sighandler(), Perl_sighandler1(), Perl_sighandler3():
 * these three function are intended to be called by the OS as 'C' level
 * signal handler functions in the case where unsafe signals are being
 * used - i.e. they immediately invoke Perl_perly_sighandler() to call the
 * perl-level sighandler, rather than deferring.
 * In fact, the core itself will normally use Perl_csighandler as the
 * OS-level handler; that function will then decide whether to queue the
 * signal or call Perl_sighandler / Perl_perly_sighandler itself. So these
 * functions are more useful for e.g. POSIX.xs when it wants explicit
 * control of what's happening.
 */


#ifdef PERL_USE_3ARG_SIGHANDLER

Signal_t
Perl_sighandler(int sig, Siginfo_t *sip, void *uap)
{
    Perl_perly_sighandler(sig, sip, uap, 0);
}

#else

Signal_t
Perl_sighandler(int sig)
{
    Perl_perly_sighandler(sig, NULL, NULL, 0);
}

#endif

Signal_t
Perl_sighandler1(int sig)
{
    Perl_perly_sighandler(sig, NULL, NULL, 0);
}

Signal_t
Perl_sighandler3(int sig, Siginfo_t *sip PERL_UNUSED_DECL, void *uap PERL_UNUSED_DECL)
{
    Perl_perly_sighandler(sig, sip, uap, 0);
}


/* Invoke the perl-level signal handler. This function is called either
 * directly from one of the C-level signals handlers (Perl_sighandler or
 * Perl_csighandler), or for safe signals, later from
 * Perl_despatch_signals() at a suitable safe point during execution.
 *
 * 'safe' is a boolean indicating the latter call path.
 */

Signal_t
Perl_perly_sighandler(int sig, Siginfo_t *sip PERL_UNUSED_DECL,
                    void *uap PERL_UNUSED_DECL, bool safe)
{
#ifdef PERL_GET_SIG_CONTEXT
    dTHXa(PERL_GET_SIG_CONTEXT);
#else
    dTHX;
#endif
    dSP;
    GV *gv = NULL;
    SV *sv = NULL;
    SV * const tSv = PL_Sv;
    CV *cv = NULL;
    OP *myop = PL_op;
    U32 flags = 0;
    XPV * const tXpv = PL_Xpv;
    I32 old_ss_ix = PL_savestack_ix;
    SV *errsv_save = NULL;


    if (!PL_psig_ptr[sig]) {
                PerlIO_printf(Perl_error_log, "Signal SIG%s received, but no signal handler set.\n",
                                 PL_sig_name[sig]);
                exit(sig);
        }

    if (PL_signals &  PERL_SIGNALS_UNSAFE_FLAG) {
        /* Max number of items pushed there is 3*n or 4. We cannot fix
           infinity, so we fix 4 (in fact 5): */
        if (PL_savestack_ix + 15 <= PL_savestack_max) {
            flags |= 1;
            PL_savestack_ix += 5;		/* Protect save in progress. */
            SAVEDESTRUCTOR_X(S_unwind_handler_stack, NULL);
        }
    }
    /* sv_2cv is too complicated, try a simpler variant first: */
    if (!SvROK(PL_psig_ptr[sig]) || !(cv = MUTABLE_CV(SvRV(PL_psig_ptr[sig])))
        || SvTYPE(cv) != SVt_PVCV) {
        HV *st;
        cv = sv_2cv(PL_psig_ptr[sig], &st, &gv, GV_ADD);
    }

    if (!cv || !CvROOT(cv)) {
        const HEK * const hek = gv
                        ? GvENAME_HEK(gv)
                        : cv && CvNAMED(cv)
                           ? CvNAME_HEK(cv)
                           : cv && CvGV(cv) ? GvENAME_HEK(CvGV(cv)) : NULL;
        if (hek)
            Perl_ck_warner(aTHX_ packWARN(WARN_SIGNAL),
                                "SIG%s handler \"%" HEKf "\" not defined.\n",
                                 PL_sig_name[sig], HEKfARG(hek));
             /* diag_listed_as: SIG%s handler "%s" not defined */
        else Perl_ck_warner(aTHX_ packWARN(WARN_SIGNAL),
                           "SIG%s handler \"__ANON__\" not defined.\n",
                            PL_sig_name[sig]);
        goto cleanup;
    }

    sv = PL_psig_name[sig]
            ? SvREFCNT_inc_NN(PL_psig_name[sig])
            : newSVpv(PL_sig_name[sig],0);
    flags |= 8;
    SAVEFREESV(sv);

    if (PL_signals &  PERL_SIGNALS_UNSAFE_FLAG) {
        /* make sure our assumption about the size of the SAVEs are correct:
         * 3 for SAVEDESTRUCTOR_X, 2 for SAVEFREESV */
        assert(old_ss_ix + 2 + ((flags & 1) ? 3+5 : 0)  == PL_savestack_ix);
    }

    PUSHSTACKi(PERLSI_SIGNAL);
    PUSHMARK(SP);
    PUSHs(sv);

#if defined(HAS_SIGACTION) && defined(SA_SIGINFO)
    {
         struct sigaction oact;

         if (sip && sigaction(sig, 0, &oact) == 0 && oact.sa_flags & SA_SIGINFO) {
               HV *sih = newHV();
               SV *rv  = newRV_noinc(MUTABLE_SV(sih));
               /* The siginfo fields signo, code, errno, pid, uid,
                * addr, status, and band are defined by POSIX/SUSv3. */
               (void)hv_stores(sih, "signo", newSViv(sip->si_signo));
               (void)hv_stores(sih, "code", newSViv(sip->si_code));
#  ifdef HAS_SIGINFO_SI_ERRNO
               (void)hv_stores(sih, "errno",      newSViv(sip->si_errno));
#  endif
#  ifdef HAS_SIGINFO_SI_STATUS
               (void)hv_stores(sih, "status",     newSViv(sip->si_status));
#  endif
#  ifdef HAS_SIGINFO_SI_UID
               {
                    SV *uid = newSV(0);
                    sv_setuid(uid, sip->si_uid);
                    (void)hv_stores(sih, "uid", uid);
               }
#  endif
#  ifdef HAS_SIGINFO_SI_PID
               (void)hv_stores(sih, "pid",        newSViv(sip->si_pid));
#  endif
#  ifdef HAS_SIGINFO_SI_ADDR
               (void)hv_stores(sih, "addr",       newSVuv(PTR2UV(sip->si_addr)));
#  endif
#  ifdef HAS_SIGINFO_SI_BAND
               (void)hv_stores(sih, "band",       newSViv(sip->si_band));
#  endif
               EXTEND(SP, 2);
               PUSHs(rv);
               mPUSHp((char *)sip, sizeof(*sip));

         }
    }
#endif

    PUTBACK;

    errsv_save = newSVsv(ERRSV);

    call_sv(MUTABLE_SV(cv), G_DISCARD|G_EVAL);

    POPSTACK;
    {
        SV * const errsv = ERRSV;
        if (SvTRUE_NN(errsv)) {
            SvREFCNT_dec(errsv_save);

#ifndef PERL_MICRO
            /* Handler "died", for example to get out of a restart-able read().
             * Before we re-do that on its behalf re-enable the signal which was
             * blocked by the system when we entered.
             */
#  ifdef HAS_SIGPROCMASK
            if (!safe) {
                /* safe signals called via dispatch_signals() set up a
                 * savestack destructor, unblock_sigmask(), to
                 * automatically unblock the handler at the end. If
                 * instead we get here directly, we have to do it
                 * ourselves
                 */
                sigset_t set;
                sigemptyset(&set);
                sigaddset(&set,sig);
                sigprocmask(SIG_UNBLOCK, &set, NULL);
            }
#  else
            /* Not clear if this will work */
            /* XXX not clear if this should be protected by 'if (safe)'
             * too */

            (void)rsignal(sig, SIG_IGN);
            (void)rsignal(sig, PL_csighandlerp);
#  endif
#endif /* !PERL_MICRO */

            die_sv(errsv);
        }
        else {
            sv_setsv(errsv, errsv_save);
            SvREFCNT_dec(errsv_save);
        }
    }

  cleanup:
    /* pop any of SAVEFREESV, SAVEDESTRUCTOR_X and "save in progress" */
    PL_savestack_ix = old_ss_ix;
    if (flags & 8)
        SvREFCNT_dec_NN(sv);
    PL_op = myop;			/* Apparently not needed... */

    PL_Sv = tSv;			/* Restore global temporaries. */
    PL_Xpv = tXpv;
    return;
}


static void
S_restore_magic(pTHX_ const void *p)
{
    MGS* const mgs = SSPTR(PTR2IV(p), MGS*);
    SV* const sv = mgs->mgs_sv;
    bool bumped;

    if (!sv)
        return;

    if (SvTYPE(sv) >= SVt_PVMG && SvMAGIC(sv)) {
        SvTEMP_off(sv); /* if it's still magical, this value isn't temporary */
        if (mgs->mgs_flags)
            SvFLAGS(sv) |= mgs->mgs_flags;
        else
            mg_magical(sv);
    }

    bumped = mgs->mgs_bumped;
    mgs->mgs_sv = NULL;  /* mark the MGS structure as restored */

    /* If we're still on top of the stack, pop us off.  (That condition
     * will be satisfied if restore_magic was called explicitly, but *not*
     * if it's being called via leave_scope.)
     * The reason for doing this is that otherwise, things like sv_2cv()
     * may leave alloc gunk on the savestack, and some code
     * (e.g. sighandler) doesn't expect that...
     */
    if (PL_savestack_ix == mgs->mgs_ss_ix)
    {
        UV popval = SSPOPUV;
        assert(popval == SAVEt_DESTRUCTOR_X);
        PL_savestack_ix -= 2;
        popval = SSPOPUV;
        assert((popval & SAVE_MASK) == SAVEt_ALLOC);
        PL_savestack_ix -= popval >> SAVE_TIGHT_SHIFT;
    }
    if (bumped) {
        if (SvREFCNT(sv) == 1) {
            /* We hold the last reference to this SV, which implies that the
               SV was deleted as a side effect of the routines we called.
               So artificially keep it alive a bit longer.
               We avoid turning on the TEMP flag, which can cause the SV's
               buffer to get stolen (and maybe other stuff). */
            sv_2mortal(sv);
            SvTEMP_off(sv);
        }
        else
            SvREFCNT_dec_NN(sv); /* undo the inc in S_save_magic() */
    }
}

/* clean up the mess created by Perl_sighandler().
 * Note that this is only called during an exit in a signal handler;
 * a die is trapped by the call_sv() and the SAVEDESTRUCTOR_X manually
 * skipped over. */

static void
S_unwind_handler_stack(pTHX_ const void *p)
{
    PERL_UNUSED_ARG(p);

    PL_savestack_ix -= 5; /* Unprotect save in progress. */
}

/*
=for apidoc_section $magic
=for apidoc magic_sethint

Triggered by a store to C<%^H>, records the key/value pair to
C<PL_compiling.cop_hints_hash>.  It is assumed that hints aren't storing
anything that would need a deep copy.  Maybe we should warn if we find a
reference.

=cut
*/
int
Perl_magic_sethint(pTHX_ SV *sv, MAGIC *mg)
{
    SV *key = (mg->mg_len == HEf_SVKEY) ? MUTABLE_SV(mg->mg_ptr)
        : newSVpvn_flags(mg->mg_ptr, mg->mg_len, SVs_TEMP);

    PERL_ARGS_ASSERT_MAGIC_SETHINT;

    /* mg->mg_obj isn't being used.  If needed, it would be possible to store
       an alternative leaf in there, with PL_compiling.cop_hints being used if
       it's NULL. If needed for threads, the alternative could lock a mutex,
       or take other more complex action.  */

    /* Something changed in %^H, so it will need to be restored on scope exit.
       Doing this here saves a lot of doing it manually in perl code (and
       forgetting to do it, and consequent subtle errors.  */
    PL_hints |= HINT_LOCALIZE_HH;
    CopHINTHASH_set(&PL_compiling,
        cophh_store_sv(CopHINTHASH_get(&PL_compiling), key, 0, sv, 0));
    magic_sethint_feature(key, NULL, 0, sv, 0);
    return 0;
}

/*
=for apidoc magic_clearhint

Triggered by a delete from C<%^H>, records the key to
C<PL_compiling.cop_hints_hash>.

=cut
*/
int
Perl_magic_clearhint(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEARHINT;
    PERL_UNUSED_ARG(sv);

    PL_hints |= HINT_LOCALIZE_HH;
    CopHINTHASH_set(&PL_compiling,
        mg->mg_len == HEf_SVKEY
         ? cophh_delete_sv(CopHINTHASH_get(&PL_compiling),
                                 MUTABLE_SV(mg->mg_ptr), 0, 0)
         : cophh_delete_pvn(CopHINTHASH_get(&PL_compiling),
                                 mg->mg_ptr, mg->mg_len, 0, 0));
    if (mg->mg_len == HEf_SVKEY)
        magic_sethint_feature(MUTABLE_SV(mg->mg_ptr), NULL, 0, NULL, FALSE);
    else
        magic_sethint_feature(NULL, mg->mg_ptr, mg->mg_len, NULL, FALSE);
    return 0;
}

/*
=for apidoc magic_clearhints

Triggered by clearing C<%^H>, resets C<PL_compiling.cop_hints_hash>.

=cut
*/
int
Perl_magic_clearhints(pTHX_ SV *sv, MAGIC *mg)
{
    PERL_ARGS_ASSERT_MAGIC_CLEARHINTS;
    PERL_UNUSED_ARG(sv);
    PERL_UNUSED_ARG(mg);
    cophh_free(CopHINTHASH_get(&PL_compiling));
    CopHINTHASH_set(&PL_compiling, cophh_new_empty());
    CLEARFEATUREBITS();
    return 0;
}

int
Perl_magic_copycallchecker(pTHX_ SV *sv, MAGIC *mg, SV *nsv,
                                 const char *name, I32 namlen)
{
    MAGIC *nmg;

    PERL_ARGS_ASSERT_MAGIC_COPYCALLCHECKER;
    PERL_UNUSED_ARG(sv);
    PERL_UNUSED_ARG(name);
    PERL_UNUSED_ARG(namlen);

    sv_magic(nsv, &PL_sv_undef, mg->mg_type, NULL, 0);
    nmg = mg_find(nsv, mg->mg_type);
    assert(nmg);
    if (nmg->mg_flags & MGf_REFCOUNTED) SvREFCNT_dec(nmg->mg_obj);
    nmg->mg_ptr = mg->mg_ptr;
    nmg->mg_obj = SvREFCNT_inc_simple(mg->mg_obj);
    nmg->mg_flags |= MGf_REFCOUNTED;
    return 1;
}

int
Perl_magic_setdebugvar(pTHX_ SV *sv, MAGIC *mg) {
    PERL_ARGS_ASSERT_MAGIC_SETDEBUGVAR;

#if DBVARMG_SINGLE != 0
    assert(mg->mg_private >= DBVARMG_SINGLE);
#endif
    assert(mg->mg_private < DBVARMG_COUNT);

    PL_DBcontrol[mg->mg_private] = SvIV_nomg(sv);

    return 1;
}

int
Perl_magic_getdebugvar(pTHX_ SV *sv, MAGIC *mg) {
    PERL_ARGS_ASSERT_MAGIC_GETDEBUGVAR;

#if DBVARMG_SINGLE != 0
    assert(mg->mg_private >= DBVARMG_SINGLE);
#endif
    assert(mg->mg_private < DBVARMG_COUNT);
    sv_setiv(sv, PL_DBcontrol[mg->mg_private]);

    return 0;
}

/*
 * ex: set ts=8 sts=4 sw=4 et:
 */