On Thu, 12 Jul 2001, Volker Philippent wrote:
> Is Exim 4 intended to use GNU Autoconf instead of several different system
> configurations, as it does now?
In my planning document, I said
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Somebody once tried to autoconf Exim, but found it too big a job. I now
have some experience with using autoconf for PCRE, and I think maybe some
use could be made of it. I don't, however, believe that all Exim build-time
configuration should be done that way. The reason is that, unlike something
like PCRE, there is quite a lot of information that is "user choice". Giving it
all as options to a configure command does not seem the best way of doing
things.
Whenever I build something that needs more than a couple of obvious options to
configure, I always save them in a file anyway, so I know what I did for
next time. Therefore, I think it is sensible to retain the current Local file
structure for all the user choice configuration.
However, it might be helpful to use autoconf to dig out various bits of
information about the operating system. At present, the OS/Makefile-* files
have hard-wired settings, and maybe this information could be figured out by
running autoconf, which would save having to keep maintaining these files.
I would arrange things so that configure is run automatically the first
time that make is run, but it would be possible to run it manually first,
to override defaults. (For example, if you have both cc and gcc
installed on your system, as I do, you need to be able to specify which to
use.) I will need to do some experiments to see exactly how this would work.
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There was some support for this position. I haven't in fact got round to
doing anything about this yet, so it may not happen in time for the
first release. Depends on how other things work out.
On Thu, 12 Jul 2001, Dr Andrew C Aitchison wrote:
> autoconf might start adding new features because I have the libraries for
> them. Just because I have pam/ldap/... installed it doesn't mean that I
> want them compiled into exim
I would use it only to determine things that are known to be different
from system to system, not for user choices like pam/ldap or which
routers/transports to include, or where to put the spool directory.
On Thu, 12 Jul 2001, Sheldon Hearn wrote:
> Good GNU configure scripts are usually chock-full of "--enable-foo"
> switches.
That's one of the problems. There are a LOT of things you can set
according to your own choice in Exim. I am not convinced that specifying
them as switches to configure is the right way to go.
> However, last time I asked Philip about this, he didn't seem too keen
> on the idea. From what I remember, he wasn't really concerned with GNU
> configure per se, but rather that his style of platform-conditional
> coding would be difficult to support with GNU configure.
Er, the whole aim of my coding style is NOT to be platform-conditional,
but instead to be feature-conditional. I've seen too much spaghetti that
is full of "if OSx and not OSy or OSz release > 6" switches in it. I
much prefer "if have featureX". I've occasionally broken my own rules,
and usually regretted it. (There once was a macro called
LINUX_IP_OPTIONS because Linux did it differently to every other OS; it
is now called GLIBC_IP_OPTIONS because it's really a glibc thing.)
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
