c++ - Printing an array of structs of structs results in an unexpected execution error? -

for struct definitions, initialize of them print contents printstruct(); after printing first element program hangs unexpectedly,

1.i thinking if malloc() fails elements right?.
2.i unfortunately have work thse structs, ideas whats wrong code below?

note: char arrays have sizes equal max length of content receive plus 1 null terminating character '\0', each team has 7 players maximum, amount of teams 21000.
sorry kind of error-checking question have never worked structs in c++ in past.

typedef struct player{ char firstname[50]; char lastname[50]; }player;  typedef struct team{     int id;     char title[50];     char summary[100];     int numberofplayers;     player *players; }team;  typedef struct teamslog{     team *arr;     int numberofteams; }teams;  int main() {    teamslog log;    log.numberofteams = 21000;    log.arr = (team*)malloc(log.numberofteams * sizeof(team));      (int = 0; < log.numberofteams; ++i)     {         (log.arr+ i)->id = 1;         (log.arr + i)->numberofplayers = 7;         (int l = 0; l < 10; ++l)         {             (log.arr + i)->summary[l] = '0' + l;             (log.arr + i)->title[l] = '0' + l;         }         (log.arr + i)->summary[10] = '\0';         (log.arr + i)->title[10] = '\0';         log.arr->players = (player*)malloc(7 * sizeof(player*));         (int l = 0; l < 7; ++l)         {             (int k = 0; k < 10; ++k){                 (log.arr + i)->players[l].firstname[k] = '0' + k;                 (log.arr + i)->players[l].lastname[k] = '0' + k;             }             (log.arr + i)->players[l].firstname[10] = '\0';             (log.arr + i)->players[l].lastname[10] = '\0';         }         printstruct(log.arr + i);      }   } 

code of printstruct():

void printstruct(team* arg) {     cout << "\nteam name: " << arg->title          << "\nid: " << arg->id          << "\nsummary: " << arg->summary          << "\nnumber of players: " << arg->numberofplayers << endl;     (int j = 0; j < arg->numberofplayers; ++j)         cout << "player " << j+1 << " " << ((arg->players) + j)->firstname << " "               << ((arg->players) + j)->lastname << endl; } 

when copy/pasted code got segfault because of following:

 log.arr->players = (player*)malloc(7 * sizeof(player*)); 

you forgot add index trying malloc memory in same spot every time go through loop, causing segfault. mentioned in comments, should using sizeof(player) instead of sizeof(player*).

following style, should be:

 (log.arr + i)->players = (player*)malloc(7 * sizeof(player)); 

i suggest making team *arr std::vector , player *players std::vector (assuming want dynamic container). vector take care of memory management (through allocator) , improve code's readability , make easier use in future (code reuse).