c++ - segmentation fault in iterator of std::list -

class declarations

struct cmp_str {  bool operator()(char const *a, char const *b)  {     return std::strcmp(a, b) < 0;  } };  class event_t { public:   event_t(string *_session_time, string *_event_type, string *_table_name, string *_num_of_events);   ~event_t();    char *table_name;    char *event_type;      pthread_mutex_t lock;    pthread_cond_t cond;    int num_of_events_threshold;    double time_out;     int num_of_events_so_far;  };   std::map <char*, std::list<event_t*>, cmp_str > all_events;  //global map 

i have function waits variable reach threshold done through pthread_cond , pthread_mutex. returns. last line gives segmentation fault.

void foo(){     //don't worry event object ic created     event_t *new_event = new event_t(args[0]->val_str(s),(args[1]->val_str(s)), (args[2]->val_str(s)), (args[3]->val_str(s)));      map<char*, list<event_t*> >::iterator map_it;       map_it = all_events.find(new_event->table_name);      if(map_it == all_events.end()){       list<event_t*> *my_list = new list<event_t*>();       my_list->push_back(new_event);       all_events[new_event->table_name] = *my_list;     }     else{       map_it->second.push_back(new_event);       (list<event_t*>::iterator list_it=map_it->second.begin(); list_it!=map_it->second.end(); ++list_it)         std::cout << (*list_it)->event_type << " " << (*list_it)->time_out << " " << (*list_it)->num_of_events_threshold << '\n';     }   /* * waiting number of events reach threshold. */     pthread_mutex_lock(&new_event->lock);      while(new_event->num_of_events_so_far < new_event->num_of_events_threshold )       pthread_cond_wait(&new_event->cond, &new_event->lock);     pthread_mutex_unlock(&new_event->lock);     // segmentation fault!!!     (list<event_t*>::iterator list_it=map_it->second.begin(); list_it!=map_it->second.end(); ++list_it)         std::cout << (*list_it)->event_type << " " << (*list_it)->time_out << " " << (*list_it)->num_of_events_threshold << '\n'; }    

if(map_it == all_events.end()){   list<event_t*> *my_list = new list<event_t*>();   my_list->push_back(new_event);   all_events[new_event->table_name] = *my_list; } 

this code doesn't leave map_it pointing valid iterator, when dereference @ bottom of function crash.

you want add line like

map_it = all_events.find(new_event->table_name); 

inside if { } clause.