pkg-config version confusion

[William Pitcock]

Hi,

On Fri, Jan 5, 2018 at 7:12 PM, Jeffrey Walton <noloader at gmail.com> wrote:
> On Fri, Jan 5, 2018 at 12:53 PM, William Pitcock
> <nenolod at dereferenced.org> wrote:
>> ...
>>> When I check my Fedora 26 x86_64 machine:
>>>
>>>     $ command -v pkg-config
>>>     /bin/pkg-config
>>>     $ pkg-config --version
>>>     1.3.12
>>>
>>> But when I check the pkg-config download at
>>> https://pkgconfig.freedesktop.org/releases are it says the latest
>>> version is 0.29.2 from MARCH 2017.
>>>
>>> Does anyone know what is going on with the version information? Is
>>> 1.3.12 newer or older than 0.29.2?
>>
>> This is pkgconf 1.3.12 (my implementation).  Some distributions use it
>> now because they can take advantage of libpkgconf in various build
>> tools, etc.
>>
>> 1.3 is the latest release of pkgconf 1.3 series, there is also a 1.4
>> series that recently went into Fedora rawhide.
>
> Thanks William.
>
> Please forgive my ignorance with these questions.
>
> When upgrading pkg-config, what are the rules of the road? Should we
> stay with the original lineage (Freedesktop vs Pitcock); or can they
> be mixed and matched? That is, are these valid transitions/upgrades:
>
> * Start with Freedesktop -> move to Pitcock
> * Start with Pitcock -> move to Freedesktop

You could use any implementation you want, as long as it is reasonably
conformant.
There are other implementations written in various scripting
languages, even, but those vary in amount of conformance.

Also, you can check if a pkg-config is pkgconf or pkg-config by doing
`pkg-config --modversion pkgconf`, if you want to be absolutely
certain.
A .pc file can also declare a requirement on pkgconf if it uses
pkgconf extensions in the obvious way.

William