On Sat, 6 Oct 2012 17:01:57 -0700, "Ronald S. Bultje" <[email protected]> 
wrote:
> Hi,
> 
> On Sat, Oct 6, 2012 at 1:28 PM, Anton Khirnov <[email protected]> wrote:
> > On Sat, 6 Oct 2012 12:35:44 -0700, "Ronald S. Bultje" <[email protected]> 
> > wrote:
> >> On Sat, Oct 6, 2012 at 9:58 AM, Anton Khirnov <[email protected]> wrote:
> >> > ---
> >> >  avprobe.c         |    6 +++---
> >> >  cmdutils.c        |   16 +++++++++++-----
> >> >  tools/graph2dot.c |    4 ++--
> >> >  3 files changed, 16 insertions(+), 10 deletions(-)
> >> >
> >> > diff --git a/avprobe.c b/avprobe.c
> >> > index 16a5d29..3a3ae0f 100644
> >> > --- a/avprobe.c
> >> > +++ b/avprobe.c
> >> > @@ -584,6 +584,7 @@ static void show_stream(AVFormatContext *fmt_ctx, 
> >> > int stream_idx)
> >> >      const char *profile;
> >> >      char val_str[128];
> >> >      AVRational display_aspect_ratio;
> >> > +    const AVPixFmtDescriptor *desc;
> >> >
> >> >      probe_object_header("stream");
> >> >
> >> > @@ -629,9 +630,8 @@ static void show_stream(AVFormatContext *fmt_ctx, 
> >> > int stream_idx)
> >> >                            rational_string(val_str, sizeof(val_str), ":",
> >> >                            &display_aspect_ratio));
> >> >              }
> >> > -            probe_str("pix_fmt",
> >> > -                      dec_ctx->pix_fmt != AV_PIX_FMT_NONE ?
> >> > -                      av_pix_fmt_descriptors[dec_ctx->pix_fmt].name : 
> >> > "unknown");
> >> > +            desc = av_pix_fmt_desc_get(dec_ctx->pix_fmt);
> >>
> >> I think this is an awful idea, it should be OK to access the array 
> >> directly.
> >>
> >
> > I don't see any advantage to accessing the array directly.
> 
> It often leads to smaller code. Instead of AVPixFmtDesc *d =
> getter(pix_fmt); if (!d) return -1; printf("%d\n", d->something);, you
> can just do printf("%d\n", array[pix_fmt].something);. Do we really
> need to babysit our users?

Checking for d to be non-NULL is equivalent to checking that pix_fmt is
valid. So no, it does not necessarily makes the code longer.
> 
> > It is the only case in all Libav where we export an array like this.
> 
> We never supported MSVC. So we shouldn't?
> 

YES! =p

Seriously though, there are only disadvantages to exporting the array
directly.

> > It fixes the size of AVPixFmtDescriptor for no good reason.
> 
> Is there a need to extend it?
> 

There might be. You don't want to find out that you need to extend it
two months after somebody else just bumped lavu.

> > It prevents the caller from accessing all the descriptors when he's
> > using a newer library than the one he compiled against.
> 
> if (compile_ver > runtime_ver) error(); on app init. Likely, you want
> to do that anyway.
> 
> > And I hear there's some trouble with the evil microsoft thing and data
> > symbols.
> 
> You have that anyway for any symbol shared between lavu/f/fi/c/r/*.

It should be our long-term goal to remove those.

-- 
Anton Khirnov
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