XS: how to destroy HV* that was used internally?

[OlegG]

Suppose I have following class implemented with XS

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "ppport.h"

typedef struct {
    HV* set;
    char foo;
} My_Class;

MODULE = My::Class    PACKAGE = My::Class

SV*
new(char* class)
    PREINIT:
        My_Class *self;
    CODE:
        Newx(self, 1, My_Class);
        self->set = newHV();
        self->foo = 0;

        RETVAL = newSV(0);
        sv_setref_pv(RETVAL, class, (void *)self);
    OUTPUT:
        RETVAL

void
DESTROY(My_Class *self)
    CODE:
        /* HOW TO DESTROY self->set HERE*/
        Safefree(self);

Where I'll use self->set internally, which type is HV*. In the constructor (new) newHV() creates HV with reference count 1. So, as I understand, to be destroyed reference count should be decreased to 0. But as I found we have only SvREFCNT_dec() which argument may be SV* and not HV*.

So, what is a solution here?
May be I just need to call Safefree(self->set)?
Or get reference to self->set into SV* variable and call SvREFCNT_dec on it?

[salva]

SvREFCNT_dec((SV*)hv);

All internal Perl data structures are derived from SV, so that you can do thinks like that.

[OlegG]

Thank you!
Also found that for me it works without type casting. But, ok, I'll use it
And after all I found similar question on stackoverflow with similar answer.

[ikegami]

That's because SvREFCNT_dec already casts for you. In fact, it casts in a way that will detect if the input was const, so doing SvREFCNT_dec((SV*)hv) instead of SvREFCNT_dec(hv) is actually harmful.

If you ever use (SV*)x, consider using MUTABLE_SV(x) instead.