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Subject: Re: [Boost-build] gcc.jam weirdness (was: Boost-1.36.0 FreeBSD patches for review)
From: Steve M. Robbins (steve_at_[hidden])
Date: 2008-10-24 23:13:02

On Fri, Oct 24, 2008 at 09:30:42AM -0400, Alexander Sack wrote:
> On Fri, Oct 24, 2008 at 4:04 AM, Steve M. Robbins <steve_at_[hidden]> wrote:
> > On Thu, Oct 23, 2008 at 10:46:58PM -0400, Alexander Sack wrote:
> >
> >> In the meantime, I would like comments on the following three patches:
> >
> >> - gcc.jam.patch
> >>
> >> The gcc toolset is set with a LD_LIBRARY_PATH without /lib.
> >
> > My reading of the linux runtime loader manpage suggests that
> > LD_LIBRARY_PATH should be reserved for *NONSTANDARD* library
> > locations. Here is an excerpt from "man ld-linux":
> >
> > The necessary shared libraries needed by the program are searched
> > for in the following order
> >
> > o Using the environment variable LD_LIBRARY_PATH
> > (LD_AOUT_LIBRARY_PATH for a.out programs). Except if the
> > executable is a setuid/setgid binary, in which case it is
> > ignored.
> >
> > o From the cache file /etc/ which contains a compiled
> > list of candidate libraries previously found in the augmented
> > library path.
> >
> > o In the default path /lib, and then /usr/lib.
> >
> >
> > In my view, it would be a mistake to add /lib. Alexander: what
> > problem does that solve for you?

> 2) The default even on Linux and gcc's rtld is /lib as you can see
> above. Putting it in /lib is not wrong in my book but it may not
> achieve what this line is really looking for (well get to that in a
> sec)

Yes: the run-time loader searches /lib, /usr/lib, and the like. Since
LD_LIBRARY_PATH is for *NONSTANDARD* locations, you *do* *not* put
/lib into it.

In general, LD_LIBRARY_PATH is empty; it is mainly useful to kludge
around a poorly-set up system. For example, if someone installs
shared libs in /some/weird/place that isn't placed into by
the admin.

> When you set the LD_LIBRARY_PATH to search
> /usr/lib:/usr/lib32:/usr/lib64 what occurs is rtld picks up the
> version for /usr/lib32 SINCE there exists the major number version of
> say and barfs.

Sure; my propsal is NOT to set the LD_LIBRARY_PATH variable at all. The
system will do the right thing.


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