On Mon, Feb 25, 2002 at 07:32:30PM +0100, Akim Demaille wrote: > >>>>> "Zack" == Zack Weinberg <[EMAIL PROTECTED]> writes: > > Zack> It may well be good enough. I cannot test it because (a) I have > Zack> no access to any of the affected machines, and (b) for other > Zack> reasons, libstdc++ cannot currently migrate away from autoconf > Zack> 2.13. (See the discussion at > Zack> <http://gcc.gnu.org/ml/gcc-patches/2001-05/msg01986.html>; > Zack> suggestions would be appreciated.) > > I just had a look, and could find exactly what advice you'd like. > Also, we are working on 2.53. If you need special features, please > let us help you by specifying them!
I assume you meant "couldn't"? The show-stopper problem we had was something like this: The configure script for a target library (i.e. a library which might be being built with a just-created cross compiler) does AC_PROG_CC, but that is likely to fail with a just-created cross compiler, because we're in the process of building the runtime libraries that AC_PROG_CC will try to link against. The configure scripts and Makefiles are aware of this and do not try to do things that will not work. They have a kluge in place to prevent AC_PROG_CC from failing spuriously. The kluge does not work anymore with Autoconf 2.5x. That's fine. It provides what was intended to be a better replacement, the AC_NO_EXECUTABLES macro. Unfortunately, *any* use of AC_TRY_LINK or AC_TRY_RUN is forbidden - at generation time - in a configure.ac that uses AC_NO_EXECUTABLES, and that's too extreme. Some of the runtime libraries need to do AC_TRY_LINK tests to probe libraries that they depends on. (For instance, the C++ runtime library needs to find out some characteristics of the C runtime library.) The configure script takes precautions when it is executed to prevent spurious link failures (in the simplest case, hardwiring results to use when being cross compiled) but AC_NO_EXECUTABLES won't let us use AC_TRY_LINK at all. I'm not sure what the _right_ thing to put into autoconf 2.53 would be to solve this problem. I don't use cross compilers myself. You can look at libstdc++-v3/configure.in to see some of the things it does right now. zw
