LCA: Disintermediating distributions

Posted Feb 7, 2008 1:40 UTC (Thu) by stevenj (guest, #421) [Link]

The checks for C++ and Fortran in C-only programs was due to a libtool 1.5 bug that has since been fixed, IIRC.

And it's true that AC_PROG_CC (the check for a C compiler) automatically calls a check to make sure the compiler is in C89 (ISO C90) mode, and if not it tries to find an option to put the compiler in C89 mode. Reliably checking whether the compiler is in C89 mode involves, among other things, checks for stdio.h. These checks were still required fairly recently — e.g. on AIX circa 2003 you had to use "-qlanglvl=extc89" or it didn't handle macro parameters in completely ANSI fashion, and on HPUX the compiler was non-ANSI by default until at least the late 90s. And many of these systems were still running long, long after their release dates (e.g. I heard from Solaris users with a compiler that defaulted non-ANSI as recently as a few years ago).

When autoconf has a default check, there's usually a good reason for it; most developers don't have experience on a wide enough variety of platforms to appreciate this. Try to get a patch accepted into autoconf sometime and you'll see what they have to deal with and why so many complaints about autoconf are founded in ignorance.

(And if your configure time is dominated by the default check for an ANSI compiler, your project is pretty small indeed. As I said, in my experience most configure scripts times for projects of decent size are dominated by checks that the programmers explicitly included in response to portability problems --- or by checks that are invoked by those checks like the case above, which the autoconf developers put in there for good reason. And, really, it's not like this is a huge problem—how often do you run configure scripts, and how many seconds would you be willing to shave off at the risk of losing portability to some machine?)