dlctl
int dlctl(void *, int, void *);
int (*dlctl)(void *, int, void *);
if (_dl_cb != NULL && _dl_cb->dlctl != NULL)
return _dl_cb->dlctl(handle, command, data);
DEF_WEAK(dlctl);
PROTO_NORMAL(dlctl);
dlctl(NULL, DL_REFERENCE, dso);
dlctl(NULL, DL_SETTHREADLCK, _rthread_dl_lock);
typeof(dlctl) dlctl asm("_dlctl") __attribute__((weak));
int dlctl(void *handle, int cmd, void *data) { return 0; }
__strong_alias(_dlctl,dlctl);
.dlctl = &dlctl,