-#define PM_GETRE(o) (INT2PTR(REGEXP*,SvIVX(PL_regex_pad[(o)->op_pmoffset])))
-#define PM_SETRE(o,r) STMT_START { \
- SV* const sv = PL_regex_pad[(o)->op_pmoffset]; \
- sv_setiv(sv, PTR2IV(r)); \
+#define PM_GETRE(o) (SvTYPE(PL_regex_pad[(o)->op_pmoffset]) == SVt_REGEXP \
+ ? (REGEXP*)(PL_regex_pad[(o)->op_pmoffset]) : NULL)
+/* The assignment is just to enforce type safety (or at least get a warning).
+ */
+/* With first class regexps not via a reference one needs to assign
+ &PL_sv_undef under ithreads. (This would probably work unthreaded, but NULL
+ is cheaper. I guess we could allow NULL, but the check above would get
+ more complex, and we'd have an AV with (SV*)NULL in it, which feels bad */
+/* BEWARE - something that calls this macro passes (r) which has a side
+ effect. */
+#define PM_SETRE(o,r) STMT_START { \
+ REGEXP *const _pm_setre = (r); \
+ assert(_pm_setre); \
+ PL_regex_pad[(o)->op_pmoffset] = MUTABLE_SV(_pm_setre); \