[FFmpeg-devel] [PATCH]lavfi/avfiltergraph: Do not return ENOMEM if filter is missing
sw at jkqxz.net
Sun Jun 17 18:58:16 EEST 2018
On 16/06/18 13:39, Carl Eugen Hoyos wrote:
> 2018-02-05 3:05 GMT+01:00, James Almer <jamrial at gmail.com>:
>> On 2/4/2018 10:33 PM, Carl Eugen Hoyos wrote:
>>> OOM is unlikely as a failure for avfilter_graph_alloc_filter(), the
>>> patch avoids a surprising error if a filter was not found.
>>> Please comment, Carl Eugen
>>> From 6587726a5e96570bb54e49ccf0b7fd6d94b929c8 Mon Sep 17 00:00:00 2001
>>> From: Carl Eugen Hoyos <ceffmpeg at gmail.com>
>>> Date: Mon, 5 Feb 2018 01:43:08 +0100
>>> Subject: [PATCH] lavfi/avfiltergraph: Do not return ENOMEM if filterchain
>>> init failed.
>>> A more likely reason is that the filter was not found.
>>> libavfilter/avfiltergraph.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>> diff --git a/libavfilter/avfiltergraph.c b/libavfilter/avfiltergraph.c
>>> index 4cc6892..7ccd895 100644
>>> --- a/libavfilter/avfiltergraph.c
>>> +++ b/libavfilter/avfiltergraph.c
>>> @@ -147,7 +147,7 @@ int avfilter_graph_create_filter(AVFilterContext
>>> **filt_ctx, const AVFilter *fil
>>> *filt_ctx = avfilter_graph_alloc_filter(graph_ctx, filt, name);
>>> if (!*filt_ctx)
>>> - return AVERROR(ENOMEM);
>>> + return -1;
>> -1 is not acceptable for a public function that states it returns an
>> AVERROR value on failure.
>> If the issue is that avfilter_graph_alloc_filter() may fail because of
>> both OOM and an invalid value for filter, then I'm more inclined to use
>> AVERROR_UNKNOWN here instead.
> New patch attached.
> Please comment, Carl Eugen
There is AVERROR_FILTER_NOT_FOUND - while it isn't currently returned from lavfi, it does sound exactly right for this.
I'd prefer for it to use a function which can return an error code and propagate that (IMO the return-a-pointer style should only be used for functions which can only fail by OOM), but given the circumstances what you've written there looks fine.
(An alternative would be to check beforehand whether the filter name exists? Not sure if that's really any better.)
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