[vlc-devel] [PATCH 2/4] doc: add an option to build libvlc sample app from the documentation

Alexandre Janniaux ajanni at videolabs.io
Sat Feb 27 14:56:09 UTC 2021


On Sat, Feb 27, 2021 at 10:48:43AM +0100, Steve Lhomme wrote:
> On 2021-02-26 18:16, Alexandre Janniaux wrote:
> > Hi,
> >
> > As mentioned privately, I'm not fond of adding yet another build
> > system to build examples, especially since it won't even be testing
> > the buildsystem final users are supposed to use.
> There is not "yet another build system" in this patch.

Sorry, what? you litterally create doc/libvlc/Makefile.am
typically to build QtGL and QtPlayer with new automake
targets and even new automake rules whereas there is already
a qmake-based build system.

With that, both can now get out-of-sync with regards to the
other one, and one of them is even never used in the CI while
the other would always be used. Better remove the other one
like I mentioned then, but as I said:

 - users will never build their application from the VLC build

 - most Qt users will typically never use automake to build a
   Qt application, so it seems like a bad target for

 - in addition, it means that you need to build libvlc in order
   to build the examples, which is quite inconvenient since you
   could be able to ship the examples with a packaged libvlc.

> The final users are free to use whatever they want and that's a good reason
> not to orientate them in any favored direction.

 - and I completely agree with this point right above, which is
   why using automake within the same autoconf package is a bad
   idea, since it will never be the same environment for other
   buildsystem, by-pass potential dependency detection systems
   and thus is quite opinionated. But more on this in next

> > I'd prefer that we typically use make install to a given prefix and
> > then use qmake/foomake/etc with the correct PKG_CONFIG_PATH. The
> > alternative is to use only the automake buildsystem but to be fair,
> Last time I proposed a similar patch, RĂ©mi advised to use "noinst_" instead
> of "bin_" prefix. And IMO it makes sense not to install sample code. The
> solution you propose is the opposite, it requires to install libvlc before
> building the samples. Something that is not needed by us nor the end user
> who will need to repackage the build anyway.

There's a huge difference between "do not install the examples"
(which makes perfect sense because users generally don't need
them on their systems) and "do not install libvlc".

Typically, if you don't install libvlc, but use the mock plugins
in the examples, it might work with the automake buildsystem you
wrote but won't work with a packaged VLC and an external build
system, because mock plugin is not installed.

So I really fail to see how it's the opposite.

In addition, if libvlc needs to be repackaged (which imho is
already a flaw in our buildsystem since it bypass the make
install behaviour and is another layer above the buildsystem
which actually mimic the layer below instead of using it), then
we just need to actually package libvlc in the CI before using
it in the examples.

> > what are the odds that final users are building their application
> > inside libvlc buildsystem without having an installed package?
> Maybe it's customary on Linux (is there a separate libvlc package on Linux
> distros ?) but on Windows or Mac or Android or iOS they will need to package
> libvlc by their own means, with their build system. So the way we build it
> for ourself will not have much impact.

I don't think many people wants to be compiling libvlc
themselves, even on Windows, and especially on Windows.

But anyway say that this is true. Why use libvlc from
the build directory instead of using libvlc from the
packaged directory then?

Then, yes, we have tools to detect dependencies much like
any other platforms. We don't typically use additional
layer of dependency management like Conan but the user
might use that to provide libvlc support. By using external
build system (and actually any external buildsystem), we
show the user how it can use it to build with libvlc with
minor tweaking to the dependency layer, be it cmake, meson,
qmake, conan or anything other used on Windows. How is using
uninstalled libtool library which almost none of the above
buildsystem understand is less opinionated than using the
idiomatic buildsystem used within the community the examples
are made for?

Just so this message is clear, I'd be happy that we test the
examples in the CI and I'm glad that you initiated work
regarding that. But honestly even the previous buildsystem
was broken last time I used it and I had to fix it, I don't
want another maintenance burden there and especially if it
gives no additional value to the enduser.

The --enable-doc-samples can still be in place in configure
with much less code and without duplicating the current work.

Alexandre Janniaux

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