Review Request 126123: [Linux/Kubuntu] find udev when installing to a parallel prefix

[René J.V. Bertin]

> On Nov. 20, 2015, 1:44 p.m., Martin Gräßlin wrote:
> > The need for the change surprises me. I have been using a /opt setup for years and udev was always found. Can you show the error you hit?
> 
> René J.V. Bertin wrote:
>     Have you been using a Linux distro like Ubuntu that has multi-arch, with the actual libraries installed in `/[usr/]lib/x86_64-linux-gnu`? I guess it's also not for nothing that most FindFoo scripts appear to use the 2-stage approach where pkgconfig is queried first for hints about where to look in addition to the default locations. BTW, I'm using cmake 3.3.1 . That's not the host's default cmake which *may* have been patched to look in the multi-arch locations, but in my experience it works better to use a cmake from the target prefix (Ubuntu's Project Neon5 did the same, IIRC).
>     
>     I don't have access to the Linux system right now, but the error was that the library wasn't being found, IIRC it did find the headerfile. The error wasn't more explicit than that, my initial reaction was to check if I had the libudev-dev package installed.

Actually, my memory was wrong, the error is more perverse. Or rather, was, because I cannot seem to reproduce it now :-/

Somehow, the configure step completed without error, set `UDEV_LIBS` (to `udev`, I think), but for whatever reason the library wasn't added to the link command where it should be added. So I got a link error.

Of course I tried to rule out operator error before starting to hack the FindUDev.cmake script, but I must have missed something, or something else changed on my system since those few days ago. I seem to recall that I found a libudev.so symlink in a generic (as opposed to a multi-arch) location, but that one I can no longer find either.

So I can either discard this RR, or else it could serve as a reason investigate whether some FindFoo scripts need `pkg_check_modules` to obtain hints for `find_path` and `find_library`.


- René J.V.


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On Nov. 20, 2015, 1:41 p.m., René J.V. Bertin wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/126123/
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> 
> (Updated Nov. 20, 2015, 1:41 p.m.)
> 
> 
> Review request for KDE Frameworks and Kubuntu.
> 
> 
> Repository: solid
> 
> 
> Description
> -------
> 
> Configuring KF5 Solid under KUbuntu 14.04 for installation in a parallel prefix (/opt/local) it failed to find libudev which is installed "normally".
> 
> Modifying FindUDev.cmake to follow the same approach as other Find`*.cmake files (use pkgconfig first, and the results as hints for `find_path` and `find_library`) corrected that failure.
> 
> 
> Diffs
> -----
> 
>   cmake/FindUDev.cmake 9d0f21d 
> 
> Diff: https://git.reviewboard.kde.org/r/126123/diff/
> 
> 
> Testing
> -------
> 
> On Kubuntu 14.04.3 with Qt 5.5.1 and all of Solid 5.16.0's KF5 dependencies installed in /opt/local
> 
> 
> Thanks,
> 
> René J.V. Bertin
> 
>

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