[Discuss-gnuradio] Re: libusb error on Mac OS X when building uhd driver

[Josh Blum]

On 09/05/2010 04:11 AM, Elvis Dowson wrote:
> Hi,
>        More specifically, there is a problem with calls to 
> libusb_cpu_to_le16(x) in libusb.h
>
> /** \def libusb_cpu_to_le16
>   * \ingroup misc
>   * Convert a 16-bit value from host-endian to little-endian format. On
>   * little endian systems, this function does nothing. On big endian systems,
>   * the bytes are swapped.
>   * \param x the host-endian value to convert
>   * \returns the value in little-endian byte order
>   */
> #define libusb_cpu_to_le16(x) ({ \
>         union { \
>                 uint8_t  b8[2]; \
>                 uint16_t b16; \
>         } _tmp; \
>         uint16_t _tmp2 = (uint16_t)(x); \
>         _tmp.b8[1] = _tmp2>>  8; \
>         _tmp.b8[0] = _tmp2&  0xff; \
>         _tmp.b16; \
> })

That seems horrendous, is that even valid c code? Its better defined as 
a function, or maybe a preprocessor conditional byteswap... Is it fixed 
in the libusb10 repo at least?

-Josh