Hi Martin, Thanks for your detailed explaining. It's a good education to me.
thanks > -----Original Message----- > From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of Martin > Storsjö > Sent: Friday, August 14, 2020 3:25 AM > To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org> > Subject: Re: [FFmpeg-devel] [PATCH v3 2/3] avormat/av1dec: add low- > overhead bitstream format > > On Thu, 13 Aug 2020, James Almer wrote: > > > On 8/13/2020 3:51 AM, Xu Guangxin wrote: > > >> + > >> + ret = obu_prefetch(s, header, MAX_OBU_HEADER_SIZE); > >> + if (!ret) > >> + return AVERROR(EOF); > > > > We use AVERROR_EOF rather than AVERROR(EOF) (Afair, it was done > > because EOF is not portable, but don't quote me on it). > > Actually, it's a more severe thing than that. > > AVERROR() is used for mapping an errno style error code, EINVAL etc, which can > be either positive or negative numbers depending on platforms, to the AVERROR > range (which is negative numbers). > > So AVERROR() actually is shorthand for ERRNO_CODE_TO_AVERROR(). On > platforms where errno codes are positive (most common modern platforms > except BeOS/Haiku, iirc), it's essentially defined as (-(x)). > > Now EOF isn't an errno error code, and is defined to be a negative value > (often - > 1). So if you do AVERROR(EOF) on a system where errno codes are positive, > AVERROR(EOF) evalues to +1, which most caller would identify as not an error > at all. > > TL;DR: AVERROR(EOF) is never correct. > > // Martin > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org > with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
