[Spice-devel] [PATCH 06/22] Get rid of C-style memset initializations, use C++ style aggregates

[Christophe Fergeau]

My understanding is that the previous iteration was quite controversial,
I would just drop it from the series unless you get acks from everyone
involved this time.

Christophe

On Wed, Feb 28, 2018 at 04:43:09PM +0100, Christophe de Dinechin wrote:
> From: Christophe de Dinechin <dinechin at redhat.com>
> 
> C++-style aggregate initialization with explicit field names is more
> readable and requires less repeated typing.
> 
> Like zero initialization, aggregate initialization preserves C++ type
> safety.  However, unlike zero initialization, it does not guarantee
> that padding is properly initialized. This is not a real problem in
> our code where all padding is explicit, but it it worth keeping in
> mind.
> 
> Also note that GCC is a bit picky and will generate strange
> "unsupported" or "not implemented" errors if the fields are not all
> initialized in exact declaration order. It is useful, however, to get
> an error if a field is added and not initialized.
> 
> Writing this patch also highlighted an inconsistency between the type
> of a 'codec' local variable and the type used in the actual data
> type. Changed the type of the variable to uint8_t to match that in the
> structure declaration.
> 
> Signed-off-by: Christophe de Dinechin <dinechin at redhat.com>
> ---
>  src/spice-streaming-agent.cpp | 47 ++++++++++++++++++++++++++-----------------
>  1 file changed, 28 insertions(+), 19 deletions(-)
> 
> diff --git a/src/spice-streaming-agent.cpp b/src/spice-streaming-agent.cpp
> index acae939..7b56458 100644
> --- a/src/spice-streaming-agent.cpp
> +++ b/src/spice-streaming-agent.cpp
> @@ -221,19 +221,24 @@ write_all(int fd, const void *buf, const size_t len)
>      return written;
>  }
>  
> -static int spice_stream_send_format(int streamfd, unsigned w, unsigned h, unsigned c)
> +static int spice_stream_send_format(int streamfd, unsigned w, unsigned h, uint8_t c)
>  {
> -
> -    SpiceStreamFormatMessage msg;
> -    const size_t msgsize = sizeof(msg);
> -    const size_t hdrsize  = sizeof(msg.hdr);
> -    memset(&msg, 0, msgsize);
> -    msg.hdr.protocol_version = STREAM_DEVICE_PROTOCOL;
> -    msg.hdr.type = STREAM_TYPE_FORMAT;
> -    msg.hdr.size = msgsize - hdrsize; /* includes only the body? */
> -    msg.msg.width = w;
> -    msg.msg.height = h;
> -    msg.msg.codec = c;
> +    const size_t msgsize = sizeof(SpiceStreamFormatMessage);
> +    const size_t hdrsize  = sizeof(StreamDevHeader);
> +    SpiceStreamFormatMessage msg = {
> +        .hdr = {
> +            .protocol_version = STREAM_DEVICE_PROTOCOL,
> +            .padding = 0,       // Workaround GCC "not implemented" bug
> +            .type = STREAM_TYPE_FORMAT,
> +            .size = msgsize - hdrsize
> +        },
> +        .msg = {
> +            .width = w,
> +            .height = h,
> +            .codec = c,
> +            .padding1 = { }
> +        }
> +    };
>      syslog(LOG_DEBUG, "writing format\n");
>      std::lock_guard<std::mutex> stream_guard(stream_mtx);
>      if (write_all(streamfd, &msg, msgsize) != msgsize) {
> @@ -244,14 +249,18 @@ static int spice_stream_send_format(int streamfd, unsigned w, unsigned h, unsign
>  
>  static int spice_stream_send_frame(int streamfd, const void *buf, const unsigned size)
>  {
> -    SpiceStreamDataMessage msg;
> -    const size_t msgsize = sizeof(msg);
>      ssize_t n;
> +    const size_t msgsize = sizeof(SpiceStreamFormatMessage);
> +    SpiceStreamDataMessage msg = {
> +        .hdr = {
> +            .protocol_version = STREAM_DEVICE_PROTOCOL,
> +            .padding = 0,       // Workaround GCC "not implemented" bug
> +            .type = STREAM_TYPE_DATA,
> +            .size = size  /* includes only the body? */
> +        },
> +        .msg = {}
> +    };
>  
> -    memset(&msg, 0, msgsize);
> -    msg.hdr.protocol_version = STREAM_DEVICE_PROTOCOL;
> -    msg.hdr.type = STREAM_TYPE_DATA;
> -    msg.hdr.size = size; /* includes only the body? */
>      std::lock_guard<std::mutex> stream_guard(stream_mtx);
>      n = write_all(streamfd, &msg, msgsize);
>      syslog(LOG_DEBUG,
> @@ -424,7 +433,7 @@ do_capture(int streamfd, const char *streamport, FILE *f_log)
>  
>              if (frame.stream_start) {
>                  unsigned width, height;
> -                unsigned char codec;
> +                uint8_t codec;
>  
>                  width = frame.size.width;
>                  height = frame.size.height;
> -- 
> 2.13.5 (Apple Git-94)
> 
> _______________________________________________
> Spice-devel mailing list
> Spice-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/spice-devel
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