alignment issues

[pavel-odintsov]

Please check this: http://man7.org/tlpi/code/online/dist/filebuff/direct_read.c.html

/* memalign() allocates a block of memory aligned on an address that
       is a multiple of its first argument. By specifying this argument as
       2 * 'alignment' and then adding 'alignment' to the returned pointer,
       we ensure that 'buf' is aligned on a non-power-of-two multiple of
       'alignment'. We do this to ensure that if, for example, we ask
       for a 256-byte aligned buffer, we don't accidentally get
       a buffer that is also aligned on a 512-byte boundary. */

    buf = memalign(alignment * 2, length + alignment);
    if (buf == NULL)
        errExit("memalign");

    buf += alignment;`