# typedef struct bar*      Bar;
# typedef struct type_foo* Foo;

TYPEMAP
#######

Bar	T_NULLABLE_PTROBJ
Foo	T_NULLABLE_PTROBJ


INPUT
#####

T_NULLABLE_PTROBJ
	if ( !SvOK( $arg ) ) {  /* if not defined */
		$var = NULL;
	}
	else if ( sv_derived_from( $arg, \"${ntype}\" ) ) {
		IV tmp = SvIV( (SV*)SvRV( $arg ) );
		$var = INT2PTR( $type, tmp );
	}
	else {
		Perl_croak( aTHX_ \"$var is not of type ${ntype}\" )
	}


OUTPUT
######

T_NULLABLE_PTROBJ
	if ( $var )  /* if defined */
		sv_setref_pv( $arg, \"${ntype}\", (void*)$var );
	else
		$arg = &PL_sv_undef;

##</code><code>##

my $foo = undef;
my $bar = Foo::create_bar( $foo );

##</code><code>##

# typedef struct bar*      Bar;
# typedef struct type_foo* Foo;

# In typemap:
# Bar	T_PTROBJ
# Foo	T_PTROBJ

struct bar*
create_bar(foo_sv = 0)
	SV* foo_sv

CODE:
	struct type_foo* foo = NULL;

	if ( !foo_sv ) {
		/* Use default of NULL. */
	}
	else if ( !SvOK( foo_sv ) ) {
		/* Use default of NULL. */
	}
	else if ( sv_derived_from( foo_sv, 'type_foo' ) ) {
		IV tmp = SvIV( (SV*)SvRV( foo_sv ) );
		foo = INT2PTR( struct type_foo*, tmp );
	}
	else {
		Perl_croak( aTHX_ "\$foo is not of type foo_type" )
	}

	RETVAL = my_c_create_bar(foo);

OUTPUT:
	RETVAL