On Wed, Jun 5, 2024 at 3:18 PM Andrew Sayers <ffmpeg-de...@pileofstuff.org> wrote:
> An external API developer might think they can use AVOptions to modify > values > during playback (e.g. putting a playback quality slider next to the volume > slider). Make it clear that behaviour is not recommended. > There are options that can be changed at runtime, And it works just fine. > > Include the warning in the group description and the text for every > function > that sets options, but leave it implicit in functions that get options. > This reflects the fact that *modifying* options is likely to cause weird > bugs, > while *reading* options isn't guaranteed but is likely to be safe. > --- > libavutil/opt.h | 30 ++++++++++++++++++++++++++++-- > 1 file changed, 28 insertions(+), 2 deletions(-) > > diff --git a/libavutil/opt.h b/libavutil/opt.h > index 07e27a9208..13292c6473 100644 > --- a/libavutil/opt.h > +++ b/libavutil/opt.h > @@ -53,11 +53,16 @@ > * question is allowed to access the field. This allows us to extend the > * semantics of those fields without breaking API compatibility. > * > + * Note that AVOptions functions are not reentrant, and options may be > accessed > + * from internal FFmpeg threads. Unless otherwise noted, it is best to > avoid > + * modifying options once a struct has been initialized. > + * > * @section avoptions_scope Scope of AVOptions > * > * AVOptions is designed to support any set of multimedia configuration > options > - * that can be defined at compile-time. Although it is mainly used to > expose > - * FFmpeg options, you are welcome to adapt it to your own use case. > + * that can be defined at compile-time and set at object creation time. > Although > + * it is mainly used to expose FFmpeg options, you are welcome to adapt it > + * to your own use case. > * > * No single approach can ever fully solve the problem of configuration, > * but please submit a patch if you believe you have found a problem > @@ -483,6 +488,9 @@ typedef struct AVOptionRanges { > /** > * Set the values of all AVOption fields to their default values. > * > + * Note: like all AVOptions functions, this is not reentrant. Unless > + * otherwise noted, it should only be used before initializing the struct. > + * > * @param s an AVOption-enabled struct (its first member must be a > pointer to AVClass) > */ > void av_opt_set_defaults(void *s); > @@ -492,6 +500,9 @@ void av_opt_set_defaults(void *s); > * AVOption fields for which (opt->flags & mask) == flags will have their > * default applied to s. > * > + * Note: like all AVOptions functions, this is not reentrant. Unless > + * otherwise noted, it should only be used before initializing the struct. > + * > * @param s an AVOption-enabled struct (its first member must be a > pointer to AVClass) > * @param mask combination of AV_OPT_FLAG_* > * @param flags combination of AV_OPT_FLAG_* > @@ -661,6 +672,9 @@ enum { > * key. ctx must be an AVClass context, storing is done using > * AVOptions. > * > + * Note: like all AVOptions functions, this is not reentrant. Unless > + * otherwise noted, it should only be used before initializing the struct. > + * > * @param opts options string to parse, may be NULL > * @param key_val_sep a 0-terminated list of characters used to > * separate key from value > @@ -679,6 +693,9 @@ int av_set_options_string(void *ctx, const char *opts, > * Parse the key-value pairs list in opts. For each key=value pair found, > * set the value of the corresponding option in ctx. > * > + * Note: like all AVOptions functions, this is not reentrant. Unless > + * otherwise noted, it should only be used before initializing the struct. > + * > * @param ctx the AVClass object to set options on > * @param opts the options string, key-value pairs separated by a > * delimiter > @@ -709,6 +726,9 @@ int av_opt_set_from_string(void *ctx, const char *opts, > /** > * Set all the options from a given dictionary on an object. > * > + * Note: like all AVOptions functions, this is not reentrant. Unless > + * otherwise noted, it should only be used before initializing the struct. > + * > * @param obj a struct whose first element is a pointer to AVClass > * @param options options to process. This dictionary will be freed and > replaced > * by a new one containing all options not found in obj. > @@ -726,6 +746,9 @@ int av_opt_set_dict(void *obj, struct AVDictionary > **options); > /** > * Set all the options from a given dictionary on an object. > * > + * Note: like all AVOptions functions, this is not reentrant. Unless > + * otherwise noted, it should only be used before initializing the struct. > + * > * @param obj a struct whose first element is a pointer to AVClass > * @param options options to process. This dictionary will be freed and > replaced > * by a new one containing all options not found in obj. > @@ -764,6 +787,9 @@ int av_opt_copy(void *dest, const void *src); > * @{ > * Those functions set the field of obj with the given name to value. > * > + * Note: like all AVOptions functions, these are not reentrant. Unless > + * otherwise noted, they should only be used before initializing the > struct. > + * > * @param[in] obj A struct whose first element is a pointer to an AVClass. > * @param[in] name the name of the field to set > * @param[in] val The value to set. In case of av_opt_set() if the field > is not > -- > 2.45.1 > > _______________________________________________ > 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".