[PATCH wayland-protocols] buildsystem: add missing uninstalled pkg-config infra

[Derek Foreman]

On 30/08/16 06:09 AM, Emil Velikov wrote:
> Hi all,
> 
> On 29 August 2016 at 20:23, Derek Foreman <derekf at osg.samsung.com> wrote:
>> Hi Bryce,
>>
>> On 26/08/16 08:11 PM, Bryce Harrington wrote:
>>> On Fri, Aug 26, 2016 at 06:06:43PM -0700, Bryce Harrington wrote:
>>>> It is confusing terminology to call this 'uninstalled'; sounds like this
>>>> might remove something from your system.  'non-installed' would be more
>>>> accurate but isn't that great of a name either.
>>>
>>> Oh I see, this is pre-existing terminology in wayland.  Still not the
>>> best terminology but given there's precident I suppose this should be
>>> named consistently.
>>
>> It's actually a standard pkg-config convention.  if lala-uninstalled.pc
>> and lala.pc are both visible to pkg-config it will pick the -uninstalled
>> one first.
>>
>> It's for building/linking with uninstalled copies of libraries out of
>> their build trees.
>>
> Having gone through the pkg-config documentation, I have some
> questions on the topic:
> 
> - How should one link/use 'uninstalled' version of package ?
> cd wayland
> cd build/wayland
> ../../wayland/autogen.sh && make
> export PKG_CONFIG_PATH=...
> cd ../$projectA
> ../../$projectA/autogen.sh && make

Yup.  (You'll still need to set up LD_LIBRARY_PATH and PATH if you want
to run the stuff from those dirs)

> - Why would someone opt for such an approach ? I haven't seen such
> workflow so far.

gstreamer has scripts to automate that approach...

Reynaldo's working on a patch for wayland-build-tools to add a script
similar to one provided with gstreamer (gst-uninstalled).  We should be
submitting that for review later today.

You clone all the relevant repositories (wayland, wayland-protocols,
libinput, weston) under lalaroot/whatever/

setup the script (tell it the lalaroot location, and make a symlink to
it called wl-whatever).  Now when you run wl-whatever it starts a new
shell with LD_LIBRARY_PATH, PATH, and PKG_CONFIG_PATH set up so that you
can compile against and run the projects uninstalled from that set of
git working directories.

The symlinks allow you to set up multiple directories under lalaroot
(git, release, tags, etc...) and run the appropriate link to the script
to test a different set of working directories.

(obviously weston-launch will never be setuid when not running make install)

> - Considering the bug in the scanner -uninstalled file, plus the fact
> that (almost?) all of X related packages don't have such files - is it
> really that useful and/or used ?

I'm honestly not sure if anyone uses this stuff right now.  I think the
scanner error leads to wayland-scanner being used on $PATH instead of an
outright build failure, so it may not be a clear indication that nobody
is using this.  But it probably is :)

I'd rather see them fixed (and added) than have the functionality
removed completely - obviously my preference is skewed by the
aforementioned script.

> - If wayland-client depends on say wayland-server, should one use
> wayland-server or wayland-server-uninstalled in Required.private of
> wayland-client ?

As I understand it, you never directly reference an -uninstalled
package.  pkg-config will just use it preferentially if it finds both
foo.pc and foo-uninstalled.pc in its search path.  So you can have a set
of distro packages for wayland installed on your system, but still link
with and compile against the uninstalled versions in your git working
directories.

Thanks,
Derek
> 
> Thanks
> Emil
>