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

[Christophe de Dinechin]

> On 28 Feb 2018, at 17:36, Christophe Fergeau <cfergeau at redhat.com> wrote:
> 
> 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.

It’s a bit difficult to drop that from the series, as it is a core element of the next steps if you look carefully.


> 
> 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)
>> 
>> _______________________________________________
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>> https://lists.freedesktop.org/mailman/listinfo/spice-devel
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