int bl_getc(struct byteloader_fdata *);
int bl_read(struct byteloader_fdata *, char *, size_t, size_t);
-extern void byterun(pTHXo_ struct byteloader_state *);
+extern void byterun(pTHX_ struct byteloader_state *);
enum {
INSN_RET, /* 0 */
# define pTHX_4 4
#endif
-#ifndef pTHXo
+/* these are only defined for compatibility; should not be used internally */
+#if !defined(pTHXo) && !defined(PERL_CORE)
# define pTHXo pTHX
# define pTHXo_ pTHX_
# define aTHXo aTHX