[M3devel] pkg roots/origin/ld_library_path

[Olaf Wagner]

I understand that the $ORIGIN use in library paths does not work
if we want to have hierarchical overrides for an arbitrary set of
package pools. We'll either have to use absolute paths or rely
on a correct (automatically computed?) LD_LIBRARY_PATH setting.

How do $ORIGIN and LD_LIBRARY_PATH work together? Are there
consistently defined semantics on different systems?

Could we use $ORIGIN just for the one global system installation,
and rely on absolute paths for all other pools? Of course we'd
loose the ability to just copy from one pool to another this way,
but that may not be that important.

Anyway, we (at least I) won't work on it right now...

Olaf

Quoting Jay K <jay.krell at cornell.edu>:

>
> Really, I understand, but there is a problem nobody seems to see.
>
>
> Let's say there are multiple pkg roots.
>
>
> Remember my question? It is very important.
>   "How are the dependencies of an .so or executable found?"
>
>
> What if I install to /opt/cm3.
> You install to $HOME/cm3 -- no need for root!
> We have some root/bin/executable.
> It uses of course libm3core.so.
>
>
> I want to be able to copy it from machine to machine, probably   
> without relinking it or running some tool over it.
>
>
> People want to install libm3core.so to different places on different  
>  machines.
>
>
> Does root/bin/executable refer
> to /opt/cm3/lib?
> or $HOME/cm3/lib?
> or $ORIGIN/../lib?
> or no directory and user sets LD_LIBRARY_PATH?
>   I'm not even sure you can omit the directory.
>
>
> There is a basic contradiction here.
> $ORIGIN is good. $ORIGIN is bad.
> LD_LIBRARY_PATH is good. LD_LIBRARY_PATH is bad.
> Full paths are good. Full paths are bad.
> The ability to install to different places is good. The ability to   
> install to different places is bad.
>
>
> You cannot have all of:
>   ability to specify install location
> AND multiple package roots, where a package root is sparse
> AND if I install to a custom location, I don't have to set LD_LIBRARY_PATH
>
>
> Now, while I advocate(d) $ORIGIN and custom install locations and no  
>  need for LD_LIBRARY_PATH, that approach does devolve to everything   
> being in the same directory, which also seems not great.
>
>
> The difference is often that you don't use $ORIGIN for "well known   
> important stuff".
> You don't get "libc.so" from $ORIGIN/../lib. You get it from where   
> it always is, like /usr/lib or somesuch. You don't actually ever use  
>  a custom install for it. If you want to build your own, you are   
> probably building your own entire system, and might use chroot as   
> part of that.
>
>
> But where is the line between "my stuff" and "well known important   
> stuff"? Where is the line between stuff that can be installed   
> anywhere vs. stuff that must be installed to its "standard" location?
>
>
>  - Jay



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