Size of pointer array inside Struct

Question

I have these 2 structs :

typedef struct {
    char name[20];
    int num;
    int score;
} player;

typedef struct {
    char name[20];
    player *players;
} team;

I need to know the amount of elements stored per every *players inside my team struct. Thanks!

Then create a struct member for that (of type size_t, perhaps). — user529758
– user529758, Commented Apr 21, 2013 at 19:55
The team struct just contains a pointer to a player. This could be the first player in an array of players or it could just be a single player. How many will depend on how many you allocate when you assign some memory to that pointer. — Will
– Will, Commented Apr 21, 2013 at 19:56
@Will, i alocate 22, but the program may or may not use 22, so, then I'll realloc that memory to the amount used, then, a function needs to print how many players there are per team, so, i need a way to know how many items there're in the array itself — Dunnow
– Dunnow, Commented Apr 21, 2013 at 20:08
possible duplicate of How to find the 'sizeof'(a pointer pointing to an array)? — Bo Persson
– Bo Persson, Commented Apr 21, 2013 at 21:01

Ed Swangren · Accepted Answer · 2013-04-21 19:56:13Z

7

You can't. players is a pointer to N player instances. It carries no more information than an address. It is not an array; it is a pointer.

You will have to store the number of elements in the struct separately.

typedef struct {
    char name[20];
    player *players;
    size_t num_players;
} team;

On a side note, you had better hope that Jarrod Saltalamacchia never joins this team.

answered Apr 21, 2013 at 19:56

Ed Swangren

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8 Comments

user529758 Over a year ago

That side note! (I'd +1 this if I had any votes left for today.)

Lefteris E Over a year ago

Jarrod Saltalamacchia?? Who is that and why does he suck?

Ed Swangren Over a year ago

@LefterisE: char name[20];

Ed Swangren Over a year ago

@H2CO3: Damn it all, I was editing! :D I actually tried to find a name that was 20, but 21 was the best I could do.

Dunnow Over a year ago

the names are max 20 chars by specs, not my decission. When all works i'll change that to char *name and make it work properly, untill then, i just want it working

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