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, Apr 11 '18 at 02:37
Also, you have the arguments to [`calloc(size_t num, size_t size)`](http://en.cppreference.com/w/c/memory/calloc) backwards. — 001, Apr 11 '18 at 02:41
seems ancient version of C. Works weell in modern compilers. BTW #define style `is medicine worse than the disease` — Jacek Cz, Apr 11 '18 at 02:44
[don't cast the result of the `malloc` family in C](https://stackoverflow.com/q/605845/995714) — phuclv, Apr 11 '18 at 14:58

chux - Reinstate Monica · Accepted Answer · 2018-04-11T14:43:17.493

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];

edited Apr 11 '18 at 14:43

answered Apr 11 '18 at 03:16

Ash · Answer 2 · 2018-04-11T02:41:25.327

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.

edited Apr 11 '18 at 02:41

answered Apr 11 '18 at 02:40

Ash

2 Answers2