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

[Christophe de Dinechin]

> On 1 Mar 2018, at 10:51, Lukáš Hrázký <lhrazky at redhat.com> wrote:
> 
> On Wed, 2018-02-28 at 17:36 +0100, Christophe Fergeau 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.
> 
> I've only commented on compiler support, it seems it's fine, so no
> problem for me. I'll leave the ack to Frediano, he understands better
> the padding issues.
> 
>> 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
> 
> "it is”.

Fixed

> 
>>> 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? */
> 
> The question in the comment? :)

It was in the original. Not sure why.

> 
>>> +        },
>>> +        .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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>>> Spice-devel mailing list
>>> Spice-devel at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/spice-devel
>> 
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