Samba 4.9 still uses e.g. tevent_context_is_wrapper() or tevent_context_same_loop() however in tevent 0.9.39 those functions are inside a

#ifdef TEVENT_DEPRECATED
#endif

which means that you can compile errors like:

../source3/lib/messages_ctdb.c: In function ‘messaging_ctdb_register_tevent_context’:         
../source3/lib/messages_ctdb.c:248:7: error: implicit declaration of function ‘tevent_context_same_loop’; did you mean ‘tevent_context_init_ops’? [-Werror=implicit-function-declaration]
  248 |   if (tevent_context_same_loop(fde_ev->ev, ev)) {                                                                                                                                    
      |       ^~~~~~~~~~~~~~~~~~~~~~~~                                                                                                                                                       
      |       tevent_context_init_ops                                                         
../source3/lib/messages_ctdb.c:256:7: error: implicit declaration of function ‘tevent_context_is_wrapper’; did you mean ‘tevent_context_init_ops’? [-Werror=implicit-function-declaration]   
  256 |   if (tevent_context_is_wrapper(ev)) {                                                
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~                                                       
      |       tevent_context_init_ops                                                                                                                                                        
cc1: some warnings being treated as errors                                                                                                                                                   
../source3/lib/messages.c: In function ‘messaging_register_event_context’:                                                                                                                   
../source3/lib/messages.c:211:7: error: implicit declaration of function ‘tevent_context_same_loop’; did you mean ‘tevent_context_init_ops’? [-Werror=implicit-function-declaration]         
  211 |   if (tevent_context_same_loop(reg->ev, ev)) {                                                                                                                                       
      |       ^~~~~~~~~~~~~~~~~~~~~~~~                                                                                                                                                       
      |       tevent_context_init_ops                                                                                                                                                        
../source3/lib/messages.c: In function ‘messaging_init_internal’:                                                                                                                            
../source3/lib/messages.c:503:6: error: implicit declaration of function ‘tevent_context_is_wrapper’; did you mean ‘tevent_context_init_ops’? [-Werror=implicit-function-declaration]
  503 |  if (tevent_context_is_wrapper(ev)) {                                                                                                                                                
      |      ^~~~~~~~~~~~~~~~~~~~~~~~~                                                                                                                                                       
      |      tevent_context_init_ops