vla.zig

const std = @import("std");

const some_cond = false;
const My_Vla_Struct = struct {
    x: if (some_cond) i32 else void,

    const Self = @This();

    pub fn usefulMethod(self: *Self) void {
        // ...
    }

    // object is followed by variable length array
};
const ListType = std.LinkedList(My_Vla_Struct);

fn newNode(allocator: *std.mem.Allocator, extra_size: usize) !*ListType.Node {
    const node_ptr = try allocator.alignedAlloc(u8, @alignOf(ListType.Node), @sizeOf(ListType.Node) + extra_size);
    return @ptrCast(*ListType.Node, node_ptr.ptr);
}

test "vla" {
    const node = try newNode(std.debug.global_allocator, 10);
    // const vla_ptr = @ptrCast([*]u8, &node.data); // zig: /build/zig/src/zig-0.4.0/src/codegen.cpp:6083: LLVMOpaqueValue* gen_const_val(CodeGen*, ConstExprValue*, const char*): Assertion `type_has_bits(type_entry)' failed.
    // const vla_ptr = @ptrToInt(&node.data); // error: pointer to size 0 type has no address
    const data = &node.data;
    data.usefulMethod();
    // const vla_ptr = @ptrToInt(data); // error: pointer to size 0 type has no address
    // const vla_ptr = @ptrCast([*]u8, data); // unreachable: /build/zig/src/zig-0.4.0/src/codegen.cpp:gen_const_val_ptr:5956
}