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.

In reply to Re^3: XS: how to destroy HV* that was used internally? by ikegami
in thread XS: how to destroy HV* that was used internally? by OlegG

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