libavfilter/avfilter.c:303: error: Null Dereference
  pointer `ret` last assigned on line 298 could be null and is dereferenced by call to `ff_dlog_ref()` at line 303, column 106.

libavfilter/avfilter.c:286:1: start of procedure avfilter_get_video_buffer()
284. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)
285. 
286. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
     ^
287. {
288.     AVFilterBufferRef *ret = NULL;

libavfilter/avfilter.c:288:5: 
286. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
287. {
288.     AVFilterBufferRef *ret = NULL;
         ^
289. 
290.     av_unused char buf[16];

libavfilter/avfilter.c:291:47: 
289. 
290.     av_unused char buf[16];
291.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0);
                                                   ^
292.     av_dlog(NULL, " perms:%s w:%d h:%d\n", ff_get_ref_perms_string(buf, sizeof(buf), perms), w, h);
293. 

libavfilter/avfilter.c:260:1: start of procedure ff_dlog_link()
  258. }
  259. 
  260. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
       ^
  261. {
  262.     if (link->type == AVMEDIA_TYPE_VIDEO) {

libavfilter/avfilter.c:262:9: Taking false branch
  260. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  261. {
  262.     if (link->type == AVMEDIA_TYPE_VIDEO) {
               ^
  263.         av_dlog(ctx,
  264.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:272:9: Skipping av_get_channel_layout_string(): empty list of specs
  270.     } else {
  271.         char buf[128];
  272.         av_get_channel_layout_string(buf, sizeof(buf), -1, link->channel_layout);
               ^
  273. 
  274.         av_dlog(ctx,

libavfilter/avfilter.c:262:5: 
  260. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  261. {
  262.     if (link->type == AVMEDIA_TYPE_VIDEO) {
           ^
  263.         av_dlog(ctx,
  264.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:282:1: return from a call to ff_dlog_link
  280.                 end ? "\n" : "");
  281.     }
  282. }
       ^
  283. 
  284. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)

libavfilter/avfilter.c:294:9: Taking true branch
292.     av_dlog(NULL, " perms:%s w:%d h:%d\n", ff_get_ref_perms_string(buf, sizeof(buf), perms), w, h);
293. 
294.     if (link->dstpad->get_video_buffer)
             ^
295.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
296. 

libavfilter/avfilter.c:295:9: Skipping __function_pointer__(): unresolved function pointer
293. 
294.     if (link->dstpad->get_video_buffer)
295.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
             ^
296. 
297.     if (!ret)

libavfilter/avfilter.c:297:10: Taking true branch
295.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
296. 
297.     if (!ret)
              ^
298.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
299. 

libavfilter/avfilter.c:298:9: Skipping avfilter_default_get_video_buffer(): empty list of specs
296. 
297.     if (!ret)
298.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
             ^
299. 
300.     if (ret)

libavfilter/avfilter.c:300:9: Taking false branch
298.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
299. 
300.     if (ret)
             ^
301.         ret->type = AVMEDIA_TYPE_VIDEO;
302. 

libavfilter/avfilter.c:303:47: 
301.         ret->type = AVMEDIA_TYPE_VIDEO;
302. 
303.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0); av_dlog(NULL, " returning "); ff_dlog_ref(NULL, ret, 1);
                                                   ^
304. 
305.     return ret;

libavfilter/avfilter.c:260:1: start of procedure ff_dlog_link()
  258. }
  259. 
  260. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
       ^
  261. {
  262.     if (link->type == AVMEDIA_TYPE_VIDEO) {

libavfilter/avfilter.c:262:9: Taking false branch
  260. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  261. {
  262.     if (link->type == AVMEDIA_TYPE_VIDEO) {
               ^
  263.         av_dlog(ctx,
  264.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:272:9: Skipping av_get_channel_layout_string(): empty list of specs
  270.     } else {
  271.         char buf[128];
  272.         av_get_channel_layout_string(buf, sizeof(buf), -1, link->channel_layout);
               ^
  273. 
  274.         av_dlog(ctx,

libavfilter/avfilter.c:262:5: 
  260. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  261. {
  262.     if (link->type == AVMEDIA_TYPE_VIDEO) {
           ^
  263.         av_dlog(ctx,
  264.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:282:1: return from a call to ff_dlog_link
  280.                 end ? "\n" : "");
  281.     }
  282. }
       ^
  283. 
  284. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)

libavfilter/avfilter.c:303:106: 
301.         ret->type = AVMEDIA_TYPE_VIDEO;
302. 
303.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0); av_dlog(NULL, " returning "); ff_dlog_ref(NULL, ret, 1);
                                                                                                              ^
304. 
305.     return ret;

libavfilter/avfilter.c:230:1: start of procedure ff_dlog_ref()
  228. }
  229. 
  230. static void ff_dlog_ref(void *ctx, AVFilterBufferRef *ref, int end)
       ^
  231. {
  232.     av_unused char buf[16];

libavfilter/avfilter.c:239:9: Taking false branch
  237.             ref->pts, ref->pos);
  238. 
  239.     if (ref->video) {
               ^
  240.         av_dlog(ctx, " a:%d/%d s:%dx%d i:%c iskey:%d type:%c",
  241.                 ref->video->pixel_aspect.num, ref->video->pixel_aspect.den,
