allocInner

    fn allocInner(f: *FuzzSingleThreadedAllocator, len: usize, alignment: Alignment) ?[*]u8 {
        @disableInstrumentation();

        const start_addr = alignment.forward(@intFromPtr(f.buf[f.fill..].ptr));
        const start = @as([*]u8, @ptrFromInt(start_addr)) - f.buf.ptr;
        if (start +| len > f.buf.len or f.smith.boolWeighted(31, 1)) return null;
        f.fill = start + len;
        return f.buf[start..][0..len].ptr;
    }