void sgen_client_mark_togglerefs (char *start, char *end, ScanCopyContext ctx);
void sgen_client_clear_togglerefs (char *start, char *end, ScanCopyContext ctx);
void sgen_client_mark_togglerefs (char *start, char *end, ScanCopyContext ctx);
void sgen_client_clear_togglerefs (char *start, char *end, ScanCopyContext ctx);