Why Switch a Big Software Project to autoconf?

woggo queries: "I'm a CS grad student working on a large research project (over 1 million lines of code, supported on many platforms). The project has been under development for several years, and the build system is nontrivial for end-users. We'd like to make it easier to build our software, and I'm investigating the feasibility of migrating to GNU autoconf. I need to demonstrate that the benefits of autoconf outweigh the costs of migrating a large system of makefiles with a lot of ad-hoc kludge-enabling logic. Has anyone made a similar case to their advisor/manager? Does anyone have some good 'autoconfiscation' war stories to share? (I've already seen the Berkeley amd story and the obvious links from a google search....)" Depending on the intricacies of the build process, such a conversion might take an awful lot of work. It might be easier to put a nicer face on the "nontrivial build process", although there is something to be said for the ease of "./configure; make; make install"

Comments

Beware autoconf if you are cross-compiling!!

[Stiletto]

I have found that autoconf has problems when you are cross-compiling. If you are or plan to cross-compile your project, stay far away from autoconf.

A few macros (particularly AC_TRY_RUN, and anything that calls it) compile and run a program on the host to test for functionality. Unfortunately, there is no way to tell autoconf that you aren't going to be able to run the compiled program, because it's for your target platform.

Many of the AC_FUNC_ macros simply DIE when running in a cross-compiling environment. For example, let's cross-compile the ncftp package. The configure.in uses the AC_FUNC_SETPGRP macro. Running autoconf results in:


configure.in:146: warning: AC_TRY_RUN called without default to allow cross compiling


That's right. This macro (defined elsewhere in the autoconf package) uses AC_TRY_RUN without a default clause. So instead of recovering nicely, the configure script dies when it tries to do this test. The only way to get around this is to modify /usr/share/autoconf/acspecific.m4 or not do the test!

dissenting view

[anothy]

i may well be in the minority among this crowd, but i think you should avoid autoconf like the plauge. people's most common reason for using autoconf/configure is portability, but that's a cop-out.
basically, the autoconf/configure school of portability says "forget about actually writing portable code, just write it for each variant and let the build process pick". that's whacked. you'll continually be running accross new variants, new ways in which systems are different, or just new systems. for example, i use Plan 9, which has a very good ANSI/POSIX compatability system (better than many *nix systems). despite being near-fully ANSI compliant, pretty much every autoconf fails because it doesn't recognize the output of uname or something stupid like that (of course, that says noting about when programs that claim to be ANSI or POSIX arn't, like including non-ANSI/POSIX headers, typically BSD stuff).
this school of portability also typically makes your code far less readable - littering it with ifdef's every third line - and much larger. it ends up taking much more time than just slowing down and disiplining yourself to write real portable code.
the argument 'configure ; make ; make install' is easy is stupid, as well. y'know why? 'cause 'make install' is easier. build your makefiles well. the 'install' target should have prerequisits, obviously. make will build them for install. and 'configure' is slower and more prone to failure than 'cp makefile.linux.386 makefile'. and light years more reliable. and editing an example makefile is way easier than putzing with autoconf/configure if something doesn't work. not to mention easier to debug (uh, 'echo' anyone?).

on a personal note, having done portability work a good bunch, i'd offer just a little extra advice: do not require GNU-specific stuff. don't use any of the gmake-specific features or gcc language extentions. GNU propaganda, that'll just kill your portability. and if you need something both simpler and more powerful than make, check out mk from the Plan 9 and Inferno distrubutions. Vita Nuova's got a version that runs on various unixes and win32 systems. it's very similar to make, but a bit more general and flexible. but, given that you've already got all the makefiles, i'd suggest your best bet is just sticking with plain makefiles and cleaning them up.