Re: Profile's LD_LIBRARY_PATH by default

[Sébastien Lerique]

Hello!

On 29 Oct 2020 at 10:10, david larsson 
<david.larsson@selfhosted.xyz> wrote:
> On 2020-10-28 13:49, Sébastien Lerique wrote:
> > [snip]
> > While running a racket program which uses OpenCV, I realised 
> > that my
> > LD_LIBRARY_PATH does not contain my user's profile libs. I have
> > `libopencv*.so` in `~/.guix-profile/lib/`, but running a racket
> > program which needs that fails:
> > ```
> > $ racket capture.rkt
> > ffi-lib: couldn't open "libopencv_core.so" (libopencv_core.so: 
> > cannot
> > open shared object file: No such file or directory)
> > ```
> > While running
> > ```
> > env LD_LIBRARY_PATH=/home/sl/.guix-profile/lib/ racket 
> > capture.rkt
> > ```
> > works.
> > (Also, this <http://0x0.st/ik3s.txt> is the output of `env
> > LD_DEBUG=libs racket capture.rkt`.)
> > Is this normal behaviour, i.e. that the path to dynamic libs 
> > installed
> > in my user profile should be manually configured in my shell 
> > startup
> > scripts? Should this not be included in 
> > `~/.guix-profile/etc/profile`?

> I wondered the same, and got answer in the IRC #guix that 
> setting
> LD_LIBRARY_PATH is highly discouraged (unless you have a 
> specific and
> good reason to do so in a specific case - never globally). I a 
> good explanation
> about it here:
> https://web.archive.org/web/20060719201954/http://www.visi.com/~barr/ldpath.html
>
> A good example of how it can go wrong:
>
> "In its startup script[a program called WidgetMan], it sets 
> LD_LIBRARY_PATH to
> point to its copy of Motif so it uses that one when it runs. As 
> it happens,
> WidgetMan is designed to launch other programs too. 
> Unfortunately, when
> WidgetMan launches other apps, they inherit the LD_LIBRARY_PATH 
> setting and some
> Motif based apps now break when run from WidgetMan because 
> WidgetMan's Motif is
> incompatible with (but the same library version as) the system 
> Motif library.
> Bummer!"

Yes I see that makes sense. Does this mean that one shouldn't 
install libraries in user profiles?

Or maybe that, if I were to package this racket program, then it 
would depend on `opencv` and set its required lib paths properly 
in its package definition (so work no matter if it's system-wide 
or in a user profile)?

Then, for development, is setting LD_LIBRARY_PATH still the only 
way without installing the lib system-wide?

(that's a lot of questions, apologies!)