Creates a new SV, of the type specified. The reference count for the new SV is set to 1.

Creates a new mortal SV, of the type specified. The reference count for the new SV is set to 1.

This is equivalent to SV* sv = sv_2mortal(newSV_type(<some type>)) and SV* sv = sv_newmortal(); sv_upgrade(sv, <some_type>) but should be more efficient than both of them. (Unless sv_2mortal is inlined at some point in the future.)