Re: How to write apps dependent on external libraries?

["Markus Rechberger" <mrechberger@gmail.com>]

Hey,

Ulrich Drepper has written quite alot about shared libraries. He also
did some performance tests uppon that topic.

* http://people.redhat.com/drepper/ (look at papers)
* http://udrepper.livejournal.com/

think it's better to read his papers first, bet noone will explain it
that accuratly here.

Markus

On 7/14/06, Glynn Clements <glynn@gclements.plus.com> wrote:
>
> Shriramana Sharma wrote:
>
> > Often I see apps which are dependent on this .so file or that. I don't know
> > how apps can be written that depend on libraries that are not linked into the
> > executable. So far I have been linking all needed libraries into the
> > executable.
> >
> > A .so is a collection of what?
>
> A .so (shared object) is structurally quite similar to a single .o
> file. The difference is that a .so is meant to be able to be linked at
> run-time.
>
> Linking against a .so file doesn't copy the code/data from the .o file
> to the executable; it just stores references to the .so file in the
> executable.
>
> The loader (ld-linux.so) will load any shared libraries which the
> executable requires when the executable is loaded. If it can't find
> one or more libraries, you get an error when you try to run the
> executable.
>
> > An .a is a collection of .o-s, right?
>
> It can be a collection of anything (a .a file is just an archive,
> similar to a .zip file), but it's usually just a collection of .o
> files.
>
> Linking against a .a file is similar to linking against the individual
> .o files which it contains, except that only those .o files which
> supply a required symbol (function, variable) are used.
>
> > What is a .la?
>
> A .la file is a metadata file created and used by libtool. It contains
> information (e.g. dependencies) which libtool needs to link against a
> static library.
>
> --
> Glynn Clements <glynn@gclements.plus.com>
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-- 
Markus Rechberger