Re: [FFmpeg-devel] [PATCH]lavf/hevc: Fix type specifiers

From: Carl Eugen Hoyos <ceffmpeg@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH]lavf/hevc: Fix type specifiers
Date: Sat, 3 Sep 2022 00:05:44 +0200
Message-ID: <CAB0OVGrizigmpu4MbfGOFa1i8NEH4R68nS29YO41wTabMvrfog@mail.gmail.com> (raw)
In-Reply-To: <AS8P250MB074491E6BFC3F9D3E07DB45E8F7A9@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM>

Am Fr., 2. Sept. 2022 um 23:56 Uhr schrieb Andreas Rheinhardt
<andreas.rheinhardt@outlook.com>:
>
> Carl Eugen Hoyos:
> > Fixes several warnings:
> > warning: format specifies type 'unsigned char' but the argument has type 'unsigned int'
> > ---
> >  libavformat/hevc.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/libavformat/hevc.c b/libavformat/hevc.c
> > index 1841dd5785..ca5187a92e 100644
> > --- a/libavformat/hevc.c
> > +++ b/libavformat/hevc.c
> > @@ -848,15 +848,15 @@ static int hvcc_write(AVIOContext *pb, HEVCDecoderConfigurationRecord *hvcc)
> >          if (array->numNalus == 0)
> >              continue;
> >
> > -        av_log(NULL, AV_LOG_TRACE, "array_completeness[%"PRIu8"]:               %"PRIu8"\n",
> > +        av_log(NULL, AV_LOG_TRACE, "array_completeness[%u]:               %"PRIu8"\n",
> >                 j, array->array_completeness);
> > -        av_log(NULL, AV_LOG_TRACE, "NAL_unit_type[%"PRIu8"]:                    %"PRIu8"\n",
> > +        av_log(NULL, AV_LOG_TRACE, "NAL_unit_type[%u]:                    %"PRIu8"\n",
> >                 j, array->NAL_unit_type);
> > -        av_log(NULL, AV_LOG_TRACE, "numNalus[%"PRIu8"]:                         %"PRIu16"\n",
> > +        av_log(NULL, AV_LOG_TRACE, "numNalus[%u]:                         %"PRIu16"\n",
> >                 j, array->numNalus);
> >          for (unsigned k = 0; k < array->numNalus; k++)
> >              av_log(NULL, AV_LOG_TRACE,
> > -                    "nalUnitLength[%"PRIu8"][%"PRIu16"]:                 %"PRIu16"\n",
> > +                    "nalUnitLength[%u][%u]:                 %"PRIu16"\n",
> >                     j, k, array->nalUnitLength[k]);
> >          j++;
> >      }
> > --
>
> I didn't catch this, as I didn't get a warning at all. The reason for
> this is that it is actually not problematic:
> "The ellipsis notation in a function prototype declarator causes
> argument type conversion to stop after the last declared parameter. The
> default argument
>  promotions are performed on trailing arguments." The default argument
> promotions include promoting integral types of conversion rank < int to
> int. So av_log() has to read an int/unsigned even when one uses a
> %"PRIu8". And so my inttypes.h contains this:
>
> # define PRIu8          "u"

On Windows where clang shows a warning it is
#define PRIu8        "hhu"

See "Size Prefixes" in
https://docs.microsoft.com/en-us/cpp/c-runtime-library/format-specification-syntax-printf-and-wprintf-functions

> # define PRIu16         "u"
> # define PRIu32         "u"
>
> No wonder neither GCC nor Clang warned about this.

> Anyway, patch LGTM.

Please push, I currently have no access to my development system.

Thank you, Carl Eugen
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