-int X509_CRL_get_ext_count(X509_CRL *x);
-int X509_CRL_get_ext_by_NID(X509_CRL *x, int nid, int lastpos);
-int X509_CRL_get_ext_by_OBJ(X509_CRL *x, ASN1_OBJECT *obj, int lastpos);
-int X509_CRL_get_ext_by_critical(X509_CRL *x, int crit, int lastpos);
-X509_EXTENSION *X509_CRL_get_ext(X509_CRL *x, int loc);
+int X509_CRL_get_ext_count(const X509_CRL *x);
+int X509_CRL_get_ext_by_NID(const X509_CRL *x, int nid, int lastpos);
+int X509_CRL_get_ext_by_OBJ(const X509_CRL *x, ASN1_OBJECT *obj, int lastpos);
+int X509_CRL_get_ext_by_critical(const X509_CRL *x, int crit, int lastpos);
+X509_EXTENSION *X509_CRL_get_ext(const X509_CRL *x, int loc);