Notes & warning after update.

Sriranga Veeraraghavan sriranga at
Mon Oct 11 20:54:03 UTC 2021

Hi Greg,

I am by no means a macports expert, but based on my experience, I think you can ignore the warnings.  AFAIK, the warnings are telling you the following:

1. The first message you received regarding ffmpeg indicates that ffmpeg was built with modules that are licensed under the GNU Public License (GPL).  As the message states, these modules are:

postproc - video postprocessing 
libx264 - library for handling H.264/MPEG-4 AVC format video
libx265 - library for handling H.265/HEVC format video
libxvid - library for handling Xvid MPEG-4 Part 2 video

The message about ffmpeg next tells you that if you want to include libraries that are not considered freely distributable for the purposes of the GPL (I think that this is currently only the Fraunhofer AAC code: <>), then you should rebuild the ffmpeg port with the +nonfree option, which I think you could do as follows:

sudo port deactivate ffmpeg && sudo port install ffmpeg +nonfree

Finally, the message about ffmpeg tells you that if you don’t want the GPL libraries mentioned above, you should rebuild the ffmpeg port without the +gpl2 option (which appears to the be default, and which I normally prefer to install because my camera captures video in H.264/H.265).  I think you could do this as follows:

sudo port deactivate ffmpeg && sudo port install ffmpeg -gpl2

2. The second message you received regarding python27 tells you how to make python 2.7 the default version of python and/or python2, in other words, the version that would get run if you typed python and/or python2 (assuming that /opt/local/bin comes before /usr/bin in your $PATH).  

Unless you are using python 2.7 regularly or have a specific reason not to use the Apple provided version of python/python2, I am not sure if you really need to do either of these things (I never have, and I’ve been using macports for years).

3. The third message you received regarding python39 is similar to the message you received about python27 and tells you how to make python 3.9 the default version of python and/or python3.  If you are working with python3, you may want to do this. 

4. The message you received from ’sudo port upgrade outdated’ tells you that when the links port, which is installed on your system, was built, the '-Wimplicit-function-declaration’ option was supplied to the compiler and that the compiler found three functions that were implicitly declared.  The warning is telling you that it is possible that  links may not function properly in some situations because of this.  

[If you are familiar with C, apologies in advance for the following paragraph, including inaccuracies due to oversimplification] 

These days, well-formed C requires a description of a function (called a prototype) to be provided before a function is used for the first time.  If a function is used without providing a prototype, when the '-Wimplicit-function-declaration’ option is supplied to the computer, the compiler tells you that you that there may be something wrong with your program.  In this case, my guess is that somewhere in the links source code the standard C header file string.h should have been included but wasn’t (either due to oversight or because of a configuration error), and the compiler is highlighting this.  This is probably something that should be fixed in the links source code, but could possibly be fixed by macports as well.



> On Oct 11, 2021, at 10:53, Greg Bell <gregjbell at> wrote:
> Hello folks.
> I have just ran this…
> sudo port selfupdate && sudo port upgrade youtube-dl
> upon completion I have three notes and I'm not sure how to address them (what to do)?
> ffmpeg has the following notes:
>    This build of ffmpeg includes GPLed code and is therefore licensed under GPL
>    v2 or later.
>    The following modules are GPLed:
>      postproc
>      libx264
>      libx265
>      libxvid
>    To include all nonfree, GPLed and LGPL code use variant +nonfree.
>    To remove nonfree and GPLed code leaving only LGPL code remove the +gpl2
>    variant.
> python27 has the following notes:
>    To make this the default Python or Python 2 (i.e., the version run by the
>    'python' or 'python2' commands), run one or both of:
>        sudo port select --set python python27
>        sudo port select --set python2 python27
> python39 has the following notes:
>    To make this the default Python or Python 3 (i.e., the version run by the
>    'python' or 'python3' commands), run one or both of:
>        sudo port select --set python python39
>        sudo port select --set python3 python39
> ------------
> Also after running…
> sudo port upgrade outdated
> I received a Warning. Is this something to be concerned about?
> Warning: Configuration logfiles contain indications of -Wimplicit-function-declaration; check that features were not accidentally disabled:
>  memmem: found in links-2.24/config.log
>  memrchr: found in links-2.24/config.log
>  strnlen: found in links-2.24/config.log
> ------------
> Apologies for the schoolboy questions.
> Greg.

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