#define GvCV(gv) (GvGP(gv)->gp_cv)
#define GvCVGEN(gv) (GvGP(gv)->gp_cvgen)
-#define GvCVu(gv) (GvGP(gv)->gp_cvgen ? Nullcv : GvGP(gv)->gp_cv)
+#define GvCVu(gv) (GvGP(gv)->gp_cvgen ? NULL : GvGP(gv)->gp_cv)
#define GvLINE(gv) (GvGP(gv)->gp_line)
#define GvFILE(gv) (GvGP(gv)->gp_file)