-extern ecdh_t *ecdh_generate_public(void *pubkey) __attribute__ ((__malloc__));
-extern bool ecdh_compute_shared(ecdh_t *ecdh, const void *pubkey, void *shared);
-extern void ecdh_free(ecdh_t *ecdh);
+ecdh_t *ecdh_generate_public(void *pubkey) __attribute__((__malloc__));
+bool ecdh_compute_shared(ecdh_t *ecdh, const void *pubkey, void *shared) __attribute__((__warn_unused_result__));
+void ecdh_free(ecdh_t *ecdh);