Static Variables

Static variables are global variables declared at the top level of a program. They require the static keyword and are immutable by default.

Declaration

static i32 MAX_SIZE = 1024;
static i32 DEFAULT_PORT = 8080;

Static variables must have an initializer that can be evaluated at compile time (integer, float, or string literals, and simple constant expressions).

Mutable Static Variables

Use mut to declare a mutable static variable:

static mut i32 counter = 0;

void increment() {
    counter = counter + 1;
}

i32 main() {
    increment();
    increment();
    increment();
    return counter; // 3
}

Without mut, attempting to assign to a static variable is an error.

Namespaces

Static variables participate in the namespace system. When declared inside a namespaced file, they are accessible via their qualified name:

// in config.djinn
namespace app::config;

static i32 MAX_CONNECTIONS = 100;

// in main.djinn
import app::config;

i32 main() {
    return app::config::MAX_CONNECTIONS;
}

Usage with Macros

Static variables work naturally with macros:

macro log {
    (debug, expression msg) => { trace(msg) }
    (off, expression msg)   => void
}

static mut i32 log_count = 0;

void trace(i32 val) {
    log_count = log_count + val;
}

i32 main() {
    log(debug, 10);
    log(off, 99);
    return log_count; // 10
}

Comparison with constexpr

Use constexpr for values that never change and benefit from inlining. Use static for global state that functions need to read and write.