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Re: Question regarding interdependent convenience libraries

From: Ralf Wildenhues
Subject: Re: Question regarding interdependent convenience libraries
Date: Thu, 3 May 2007 08:42:56 +0200
User-agent: Mutt/1.5.15 (2007-04-13)

* Bob Friesenhahn wrote on Thu, May 03, 2007 at 06:00:22AM CEST:
> On Wed, 2 May 2007, Scott D. Fleming wrote:
>> Is libtool or the underlying linker smart enough to recognize and
>> ignore the duplicate libraries?
> I think that the content of convenience libraries is extracted into 
> individual .o files prior to being used for linkage.

This is true if the linker doesn't have a functionality similar to
--whole-archive, and if the resulting output is a library, rather than a

> They are not used for 
> linking like traditional archive libraries.  This means that any duplicates 
> would result in individual .o files being overwritten prior to use.

This is not true.  When extracted, object files with identical names are

> In other words non-fatal for building applications. However, if you
> build installed libraries based on these convenience libraries, you
> could run into trouble if two installed libraries included some of the
> same objects.

The rule of thumb is to put each convenience archive in at most one
library, and never into a program.  (Convenience archives do not end
up as whole in a program; if that is not a problem for you, then that
part should be ok.)

> A radically-different solution is to use a non-recursive Makefile scheme.  
> This eliminates the need for convenience libraries entirely and speeds up 
> the build.  Automake does support this reasonably well and you can use 
> Makefile includes to still keep Makefile fragments alongside the sources.  
> However, the Makefile fragments require "namespacing" as if everything is 
> referenced from the top level Makefile (which they will be).

This is a good suggestion.


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