Re: [gentoo-dev] Slotting Tcl/Tk

[Stanislav Brabec <utx@gentoo.org>]

On Fri, Nov 21, 2003 at 02:42:10AM +0000, Eamon Caddigan wrote:
> Howdy, y'all.
> 
> I rekkon it's time we reopen bug #4450. I thought I'd post it to
> gentoo-dev because a) tcl/tk is important, and can break a lot of stuff
> and b) I'm relatively inexperienced with writing ebuilds, and would
> appreciate comments and suggestions. 
> 

SLOTting packages, which provides identical interface and cannot seamlessly
co-exist in system, is bad idea.

You can have installed two packages using two SLOTs in one time. But if you
update or install anything, current packages/ebuilds have no intelligence to
guess, for which SLOT they should be compiled. It will compile for this SLOT,
which has created actual instances of /gentoo/usr/lib/*Config.sh!

Two tcl/tk versions are partially acceptable for binary-only distributions
where different soname is reasonable protection. But for systems compiled from
source, risks of version mismatch is very high.

Tcl/tk extensions built randomly for tcl/tk 8.3 and 8.4 will not work well when
they are combined.

Summary:

Tcl/tk slots is bad idea. It can change only if somebody will hack all
dev-lang/tcl (and some extra) ebuilds to be able to create simultaneously
packages for both tcl/tk 8.3 and 8.4 (if they support building for both
versions).

---

Tcl/tk situation is NOT similar to Apache 1/2 or GNOME 1/2, which has 
different interfaces and different library names.

This situation is very similar to libc5 and glibc few years ago - yes, you can 
install both in one system. Yes, existing packages will continue to work. But 
oops - new packages using one library compiled for libc5 and one for glibc
will most probably crash.

There is a chance for simple SLOTting - using /opt/prefix for alternative tcl 
versions. In such case you have to install all extensions twice - once for main
system, once for alternative. For more, see insight ebuild.

-- Stanislav Brabec

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