Zig 0.17.0-dev (Split by item)

This is an example of documentation generated by ZigDoc, an alternative to Zig's built-in Auto Doc feature. See also examples in other modes/formats. The project being documented here (as the example) is the Zig library itself.

free

ArenaAllocator.free

fn free(ctx: *anyopaque, memory: []u8, alignment: Alignment, ret_addr: usize) void

File

lib/std/heap/ArenaAllocator.zig:608

Code

fn free(ctx: *anyopaque, memory: []u8, alignment: Alignment, ret_addr: usize) void {
    const arena: *ArenaAllocator = @ptrCast(@alignCast(ctx));
    _ = alignment;
    _ = ret_addr;

    assert(memory.len > 0);

    const node = arena.loadFirstNode().?;
    const buf_ptr = @as([*]u8, @ptrCast(node)) + @sizeOf(Node);

    const cur_end_index = @atomicLoad(usize, &node.end_index, .monotonic);

    if (buf_ptr + cur_end_index != memory.ptr + memory.len) {
        // Not the most recent allocation; we cannot free it.
        return;
    }

    const new_end_index = cur_end_index - memory.len;
    assert(buf_ptr + new_end_index == memory.ptr);

    _ = @cmpxchgStrong(
        usize,
        &node.end_index,
        cur_end_index,
        new_end_index,
        .release, // release freed memory
        .monotonic,
    );
}