Re: Including static libraries in shared libraries with libtool.

[Howard Chu]

Bob Friesenhahn wrote:
> On Sun, 26 Sep 2004, Simon Richter wrote:
>
> > > 1. Libtool takes _all_ modules from libauth.la, and puts them into
> > > libauthuserdb.la.  I only want the modules that libauthuserdb.la 
> > > actually
> > > needs.
> >
> >
> > A "convenience library", as a libtool library that is not installed is
> > called, is linked into each object that uses it. If the object is a
> > library, it is copied completely, otherwise, it is linked statically.
> > This feature is intended for huge libraries that are built from multiple
> > subdirectories, where each subdir builds a convenience lib and
> > everything is linked in the end.

> Using recent Automake, I find that I am able to eliminate use of 
> convenience libraries by using a non-recursive build and referring to 
> sources in subdirectories.  A simple Automake macro refers to all the 
> objects which would be equivalent to a convenience "library".  Works 
> great and avoids the overhead imposed by libtool since libtool must 
> extract all the objects from the archive file prior to using them.

One more time, shouting into the senseless void...

If these so-called "convenience" libraries are meant to be linked in 
whole, they should not be ar archives at all. You should just link them 
directly into a relocatable object file:
   ld -r -o <convenience.obj> *.o

The linker is faster, and it will resolve a majority of external symbol 
references immediately; i.e., all of the cross references between those 
.o files. Then when it comes time to combine all the convenience pieces 
into a single program, that step will also be faster and there's no 
wasted time extracting/deleting archive members.

And as a previous post points out, just because object files are stored 
in an archive library is no reason to assume they are non-PIC code and 
thus unusable. That was the whole point of the other thread - that there 
is no consistent way to check for PIC vs non-PIC in advance.

But again, if all you plan to do is link *all* of the objects together, 
e.g. for a shared library or for a "convenience" library, then you 
should just use "ld -r" and skip all the other intermediate crap.

This is REALLY REALLY basic ld usage practice, I'm really amazed that 
you guys keep inventing newer, harder ways to do things.
--
  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support