Re: Several questions about libtool

[Bob Friesenhahn]

On Sat, 7 Jan 2012, Russ Allbery wrote:
> > Regardless, Autoconf's configure will still make subsequent decisions
> > based on trial and error (by running the compiler and linker).
>
> Do you mean for detecting other libraries?  Only for libraries without
> pkg-config support.  You of course can't solve the whole problem

For detecting library features such as the availabilty of functions.

Over the years, Autoconf principles have not changed much.  It could 
have usefully absorbed knowledge of libtool and its installed .la 
files (but it did not).

> > Pkg-config is optional software which only really works when it is
> > properly cared for and fed correctly.
>
> The same is true of Libtool.  :)

Except that libtool is already embedded (in one vintage or another) in 
the source code of perhaps 5000 (???) different packages.  This makes 
the pace of change somewhat glacial.

> My impression is that you don't want to try to do this with magic, because
> the magic will occasionally be wrong.  That's the advantage of the
> pkg-config method.  It lets the library maintainer, who actually knows
> what's going on, specify the desired behavior.

The distribution library maintainer only knows what is going on from 
within his own limited sphere of influence.  Once the package is 
finally installed on a user's system, there is no telling what might 
happen after that.  The "user" might be the developer of the library 
that the distribution library maintainer prepares as a binary package.

Believe it or not, there are still people who download source packages 
and install software by building it from source code, or who develop 
new software from scratch, or by modifying existing source code.  Due 
to this, the pristine environment that the GNU/Linux distribution 
package maintainer is aware of is not necessarily representative of 
the user's system, or the user's intentions.  Given the principles of 
free software, we should not assume that software users will only get 
the software via carefully-prepared and managed binary packages 
provided by an OS distribution.  We should encourage people to 
actively edit source code and develop more free software or else the 
free software movement will eventually terminate by quenching the 
innovation which spawned it.  Free software should not fall victim to 
its own success.

Autotools needs to satisfy the requirements of completely different 
types of users.  This means that it still needs to work (best-effort) 
if pkg-config offers up some wrong (perhaps stale) information, or if 
the user has several independent (or complimentary) pkg-config 
installations on his system.  It also needs to work if pkg-config is 
not available at all.

You are correct that I don't put much faith in magic. :-)

I feel that I may have gotten a bit off track here, but it should be 
clear that libtool needs to err towards the most reliable mechanisms 
by default (the software should build and work by default if at all 
possible) but also provide the features that distribution maintainers 
need.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/