typedef void (*DESTRUCTORFUNC_NOCONTEXT_t) (void*);
typedef void (*DESTRUCTORFUNC_t) (pTHX_ void*);
typedef void (*SVFUNC_t) (pTHX_ SV* const);
-typedef I32 (*SVCOMPARE_t) (pTHX_ SV*, SV*);
+typedef I32 (*SVCOMPARE_t) (pTHX_ SV* const, SV* const);
typedef void (*XSINIT_t) (pTHX);
typedef void (*ATEXIT_t) (pTHX_ void*);
typedef void (*XSUBADDR_t) (pTHX_ CV *);