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From "MATHIHALLI,MADHUSUDAN (HP-Cupertino,ex1)" <>
Subject RE: Run-time linking paths via LDFLAGS on Linux with gcc.
Date Tue, 08 Jan 2002 00:38:59 GMT
This is a very good point.. (+1 for the idea if it counts).

We face a similar problem here on HPUX also.. Our requirement is slightly
different.. For ex. during my build, i pickup the system libraries from
/usr/madhum/lib/system.. In the end-user environment, the system libraries
are loaded in /usr/lib.. There's a easy method of telling the binary to
pickup the system libraries from /usr/lib at the link time by passing
certain flags to the linker.. 

We run into a similar problem that Justin is facing, and we get-around the
problem in a ugly manner by hacking the generated scripts/makefiles to
introduce these flags during the linking phase :-(.. 

I'd also be interested in knowing if there's a better method to solve this.


-----Original Message-----
From: Justin Erenkrantz []
Sent: Sunday, January 06, 2002 10:41 PM
Subject: Run-time linking paths via LDFLAGS on Linux with gcc.

gcc on Linux is brain-dead w.r.t. run-time link paths.  In order 
to add any run-time search dir, you must specify "-Wl,-rpath <path>"
to add a dir via gcc.  However, libtool only recognizes "-R" or 
"-rpath" as the link path options.  So, these two options are 
completely incompatible.  (FWIW, gcc on Solaris recognizes -R 
natively, so it isn't a problem there - -R works for both gcc
and libtool - probably why I've skirted the issue for so long.)

I usually add the Berkeley DB libraries so APR-util finds it
(SVN requires that apr-util links against db-4.0.14 which is
different than what is in my /usr/lib):

CPPFLAGS="-I/pkg/db-4.0.14/include" \
LDFLAGS="-L/pkg/db-4.0.14/lib -Wl,-rpath /pkg/db-4.0.14/lib" \
./configure ...<options>...

If we specify "-Wl,-rpath", we fail at link-time when building
the binaries, since libtool does not understand -Wl,-rpath.

However, if you specify "-R" instead of -Wl,-rpath, we will fail 
at configure-time in httpd since configure will try to link with 
LDFLAGS and gcc will say that "-R" is unrecognized.

This is a complete Catch-22.  The question is what to do about it.
I have some ideas, but I'd like to hear what other people think.

I won't prejudice you all with my proposed solutions because I
think they are all a bit unelegant.  (I'm also curious if we end 
up with what I already have.)  It looks technically feasible,
but my solutions turn into a complete mess.  Hint: we can't just 
handle this in httpd as we must build all of the subprojects (apr, 
apr-util, pcre) with the proper conversion.  It just sucks.  But, 
my builds are completely broken on Linux with -rpath LDFLAGS.  So,
we need some sort of solution.  (IMHO, ldconfig isn't a solution 
since it requires root access.)  -- justin

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