[FFmpeg-devel] [PATCH] lavu/opt: add const to av_opt_copy arg

[Michael Niedermayer]

On Sun, Nov 23, 2014 at 10:25:39PM +0100, Lukasz Marek wrote:
> On 23.11.2014 02:29, Michael Niedermayer wrote:
> >On Sun, Nov 23, 2014 at 01:01:19AM +0100, Lukasz Marek wrote:
> >>On 23.11.2014 00:58, Lukasz Marek wrote:
> >>>Signed-off-by: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> >>>---
> >>>  libavutil/opt.c | 2 +-
> >>>  libavutil/opt.h | 2 +-
> >>>  2 files changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>>diff --git a/libavutil/opt.c b/libavutil/opt.c
> >>>index 0546a37..47b1f0c 100644
> >>>--- a/libavutil/opt.c
> >>>+++ b/libavutil/opt.c
> >>>@@ -1570,7 +1570,7 @@ static int opt_size(enum AVOptionType type)
> >>>      return 0;
> >>>  }
> >>>
> >>>-int av_opt_copy(void *dst, void *src)
> >>>+int av_opt_copy(void *dst, FF_CONST_AVUTIL53 void *src)
> >>>  {
> >>>      const AVOption *o = NULL;
> >>>      const AVClass *c;
> >>>diff --git a/libavutil/opt.h b/libavutil/opt.h
> >>>index 7338e78..6b6c996 100644
> >>>--- a/libavutil/opt.h
> >>>+++ b/libavutil/opt.h
> >>>@@ -825,7 +825,7 @@ int av_opt_query_ranges(AVOptionRanges **, void *obj, const char *key, int flags
> >>>   * @param src  Object to copy into
> >>>   * @return 0 on success, negative on error
> >>>   */
> >>>-int av_opt_copy(void *dest, void *src);
> >>>+int av_opt_copy(void *dest, FF_CONST_AVUTIL53 void *src);
> >>>
> >>>  /**
> >>>   * Get a default list of allowed ranges for the given option.
> >>>
> >>
> >>I added FF_CONST_AVUTILS53 macro, but is this really needed? Cannot
> >>be just const?
> >>I'm asking because I think it doesn't fix anything.
> >>I guess is it API/ABI thing, but why?
> >
> >a user application could have a function pointer like
> >
> >all_ffmpeg_functions->opt_copy = av_opt_copy;
> >
> >and if we add const the prototype changes and this can fail to build
> >with some compiler flags or C++ or whatever
> >
> >and yes i have seen an application that had function pointers to
> >ffmpeg functions
> 
> Thx for explanation. It would be good to have option to disable this
> compability mode too. Sometimes it is not helping but annoying for
> most users.
> 
> I attached updated patch. I add const to av_next_option and
> av_opt_next to avoid warnings. It have to be applied on top of
> [PATCH 1/2] lavu/opt: handle NULL obj in av_opt_next
> 
> There is much more places it could be added in opt.c, but this would
> again trigger adding in other files (like log.h) to avoid warnings.
> 

>  opt.c |    6 +++---
>  opt.h |    6 +++---
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 8a3df1768aaaef53aa632d5515b5041e7ba7c8f0  0001-lavu-opt-add-const-to-av_opt_copy-arg-and-dependenci.patch
> From a8989702029f8c536b2153d3e6b52b1c3a9cc20f Mon Sep 17 00:00:00 2001
> From: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> Date: Sat, 22 Nov 2014 20:41:21 +0100
> Subject: [PATCH] lavu/opt: add const to av_opt_copy arg and dependencies
> 
> Signed-off-by: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> ---
>  libavutil/opt.c | 6 +++---
>  libavutil/opt.h | 6 +++---
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/libavutil/opt.c b/libavutil/opt.c
> index 5b26a00..5b305a4 100644
> --- a/libavutil/opt.c
> +++ b/libavutil/opt.c
> @@ -42,13 +42,13 @@
>  #include <float.h>
>  
>  #if FF_API_OLD_AVOPTIONS
> -const AVOption *av_next_option(void *obj, const AVOption *last)
> +const AVOption *av_next_option(FF_CONST_AVUTIL53 void *obj, const AVOption *last)

FF_CONST_AVUTIL53 is already set to const, a new
FF_CONST_AVUTIL55 would be needed

[...]

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