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Pointers

Normal pointers in Zig cannot have 0 or null as a value. They follow the syntax *T, where T is the child type.

Referencing is done with &variable, and dereferencing is done with variable.*.

fn increment(num: *u8) void {
num.* += 1;
}

test "pointers" {
var x: u8 = 1;
increment(&x);
try expect(x == 2);
}

Trying to set a *T to the value 0 is detectable illegal behaviour.

test "naughty pointer" {
var x: u16 = 0;
var y: *u8 = @ptrFromInt(x);
_ = y;
}
Test [23/126] test.naughty pointer... thread 21598 panic: cast causes pointer to be null
./test-c1.zig:252:18: 0x260a91 in test.naughty pointer (test)
var y: *u8 = @ptrFromInt(x);
^

Zig also has const pointers, which cannot be used to modify the referenced data. Referencing a const variable will yield a const pointer.

test "const pointers" {
const x: u8 = 1;
var y = &x;
y.* += 1;
}
error: cannot assign to constant
y.* += 1;
^

A *T coerces to a *const T.