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Re: Several questions about libtool

From: Bob Friesenhahn
Subject: Re: Several questions about libtool
Date: Sat, 7 Jan 2012 19:29:21 -0600 (CST)
User-agent: Alpine 2.01 (GSO 1266 2009-07-14)

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 Friesenhahn
GraphicsMagick Maintainer,

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