test:zig

guide/language/pointers.zig

@@ -0,0 +1,49 @@
+const expect = @import("std").testing.expect;
+const print = @import("std").debug.print;
+
+// 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 = 5;
+    x -= 5;
+    var y: *u8 = @ptrFromInt(x);
+    y = 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.
+
+// Pointer Sized Integers
+// `usize` and `isize` are given as unsigned and signed integers which are the same size as pointers.
+
+test "usize" {
+    try expect(@sizeOf(usize) == @sizeOf(*u8));
+    try expect(@sizeOf(isize) == @sizeOf(*u8));
+}