[FFmpeg-devel] Patch for IPC SHM

[Paul B Mahol]

On 7/23/19, Aran.Clauson at wwu.edu <Aran.Clauson at wwu.edu> wrote:
> From: Chad Fraleigh <chadf at triularity.org>
>>
>> On 7/22/2019 11:14 AM, Aran.Clauson at wwu.edu wrote:
>>
>>> +static void rm_shmid(AVFormatContext *s) {
>>> +    XCBGrabContext *c = s->priv_data;
>>> +    if(c->shmid != -1) {
>>> +      shmctl(c->shmid, IPC_RMID, 0);
>>> +      c->shmid == -1;
>>          ^^^^^^^^^^^^^^
>>   Assignment/compare operator mismatch.
>>
>>
>>> +    }
>>> +}
>>> +
>
> Well, that's embarrassing.

Do not simply concat your patch to rest of mail.

Please use git format-patch and then attach it to new mail.
Or use git send-email.

>
> diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c
> index b7e689343e..1acf3cdf28 100644
> --- a/libavdevice/xcbgrab.c
> +++ b/libavdevice/xcbgrab.c
> @@ -75,6 +75,7 @@ typedef struct XCBGrabContext {
>      const char *framerate;
>
>      int has_shm;
> +    int shmid;
>  } XCBGrabContext;
>
>  #define FOLLOW_CENTER -1
> @@ -221,6 +222,14 @@ static int check_shm(xcb_connection_t *conn)
>      return 0;
>  }
>
> +static void rm_shmid(AVFormatContext *s) {
> +    XCBGrabContext *c = s->priv_data;
> +    if(c->shmid != -1) {
> +      shmctl(c->shmid, IPC_RMID, 0);
> +      c->shmid = -1;
> +    }
> +}
> +
>  static int allocate_shm(AVFormatContext *s)
>  {
>      XCBGrabContext *c = s->priv_data;
> @@ -230,7 +239,8 @@ static int allocate_shm(AVFormatContext *s)
>
>      if (c->buffer)
>          return 0;
> -    id = shmget(IPC_PRIVATE, size, IPC_CREAT | 0777);
> +
> +    id = shmget(IPC_PRIVATE, size, IPC_CREAT | 0666);
>      if (id == -1) {
>          char errbuf[1024];
>          int err = AVERROR(errno);
> @@ -239,15 +249,20 @@ static int allocate_shm(AVFormatContext *s)
>                 size, errbuf);
>          return err;
>      }
> +
>      xcb_shm_attach(c->conn, c->segment, id, 0);
>      data = shmat(id, NULL, 0);
> -    shmctl(id, IPC_RMID, 0);
> -    if ((intptr_t)data == -1 || !data)
> -        return AVERROR(errno);
> +
> +    if ((intptr_t)data == -1 || !data) {
> +      shmctl(id, IPC_RMID, 0);
> +      return AVERROR(errno);
> +    }
>      c->buffer = data;
> +    c->shmid = id;
>      return 0;
>  }
>
> +
>  static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt)
>  {
>      XCBGrabContext *c = s->priv_data;
> @@ -268,6 +283,8 @@ static int xcbgrab_frame_shm(AVFormatContext *s,
> AVPacket *pkt)
>
>      xcb_flush(c->conn);
>
> +    rm_shmid(s);
> +
>      if (e) {
>          av_log(s, AV_LOG_ERROR,
>                 "Cannot get the image data "
>
>
>