Constant Integer and Array Initialization in C

Question

I have this expression:

const int numPlayers = 2;
player players[numPlayers];

This is an array of user-defined type players (using struct). However, I get an error saying that numPlayers has to be a constant value.

expression must have a constant value

What am I doing wrong?

I have also initialized the array like this:

player *players = (player*)calloc(sizeof(player), numPlayers);

But I cannot access any of the local variables of the struct without the program crashing.

#define numPlayers 2, declaring an int as const is not a constant for purposes of array declaration. — David C. Rankin
– David C. Rankin, Commented Apr 11, 2018 at 2:37
Also, you have the arguments to calloc(size_t num, size_t size) backwards. — 001
– 001, Commented Apr 11, 2018 at 2:41
seems ancient version of C. Works weell in modern compilers. BTW #define style is medicine worse than the disease — Jacek Cz
– Jacek Cz, Commented Apr 11, 2018 at 2:44

chux · Accepted Answer · 2018-04-11 14:43:17Z

2

In C99, the below works fine inside a function. It is a variable length array (VLA).

const int numPlayers = 2;
player players[numPlayers];

Otherwise use a #define for a true constant.

#define numPlayers 2
player players[numPlayers];

answered Apr 11, 2018 at 3:16

chux

158k17 gold badges160 silver badges311 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ash · Accepted Answer · 2018-04-11 02:41:25Z

0

const are not true constants, the compiler will not allow you to change the value only. I will suggest use #define numPlayers 2 instead.

answered Apr 11, 2018 at 2:40

Ash

4732 silver badges10 bronze badges