This should prevent attempts of using pointer before it was checked, since all modern compilers are able to spot access to uninitialized variable. No functional changes.
Previously, an empty frame object was created for an output chain that contains only sync or flush empty buffers. But since 39d7eef2e332 every DATA frame has the flush flag set on its last buffer, so there's no need any more in additional flush buffers in the output queue and they can be skipped. Note that such flush frames caused an incorrect $body_bytes_sent value.
The SPDY draft 2 specification requires that if an endpoint receives a control frame for a type it does not recognize, it must ignore the frame. But the 3 and 3.1 drafts don't seem to declare any behavior for such case. Then sticking with the previous draft in this matter looks to be right. But previously, only 8 least significant bits of the type field were parsed while the rest of 16 bits of the field were checked against zero. Though there are no known frame types bigger than 255, this resulted in inconsistency in handling of such frames: they were not recognized as valid frames at all, and the connection was closed.
There's no more need in a separate indicator of frame completeness after d74889fbf06d.
Following a24f88eff684, now the case when the FIN flag is set in SYN_STREAM is also covered.
If start time is within the track but end time is out of it, error "end time is out mp4 stts samples" is generated. However it's better to ignore the error and output the track until its end.
The ngx_cacheline_size may be too low on some platforms, resulting in unexpected hash build problems (as no collisions are tolerated due to low bucket_size, and max_size isn't big enough to build a hash without collisions). These problems aren't fatal anymore but nevertheless need to be addressed.