Re: Another snag.. extension detection

[Benoit Sigoure]

On Nov 18, 2007, at 6:42 PM, NightStrike wrote:

> On Nov 18, 2007 10:11 AM, Benoit Sigoure <address@hidden> wrote:
> > On Nov 18, 2007, at 9:02 AM, NightStrike wrote:
> >
> > > I hit another snag in my project.  I am building a runtime as a
> > > component of a cross compiler.  Configure has to determine the  
> > > various
> > > tools to use (denoted by passing --host=xx to configure), and I use
> > > all of the AC_PROG_XX macros.  This may be an autoconf issue instead
> > > of automake, but what happens is that configure tries to test for  
> > > the
> > > default extention of exe files.  The compiler doesn't make exe  
> > > files,
> > > however, because there is no runtime (chicken, egg).
> > >
> > > Will automake be ok if I just do AC_CHECK_TOOL for gcc and g++  
> > > instead
> > > of AC_PROG_CC and AC_PROG_CXX?
> >
> > Can't you populate the right cache variables to set the results you
> > want without going through the tests?  It's a kludge, but it's less
> > kludgy than what Ralf suggested, or so I think.
>
> I'm not really sure what that means, nor how to do it.  Are you
> suggesting distributing a configure cache?  Wouldn't that defeat the
> purpose of using configure?

AC_PROG_CC / CXX search for a C/C++ compiler, and your problem is  
that you can't use the compiler at configure time, right?  So what  
you want --correct me if I'm wrong-- is to use AC_PROG_CC/CXX without  
actually running the compiler, right?  In this case, you can preset  
some cache variables (shell variables of the form *_cv_*) so that  
configure doesn't run the tests that you know are going to fail.

Typically, I *guess* (untested) adding this before all your  
AC_PROG_CC/CXX/LIBTOOL and everything will trick configure:

ac_cv_c_compiler_gnu=yes
ac_cv_cxx_compiler_gnu=yes
ac_cv_objext=o
ac_cv_prog_ac_ct_CC=gcc
ac_cv_prog_ac_ct_CXX=g++
ac_cv_prog_cc_c89=
ac_cv_prog_cc_g=yes
ac_cv_prog_cxx_g=yes

The value of ac_cv_objext is obviously platform dependent and  
guessing it properly without running a compiler is fragile, at best.

For more information about cache variables, see http://www.gnu.org/ 
software/autoconf/manual/html_node/Caching-Results.html

HTH, cheers,

--
Benoit Sigoure aka Tsuna
EPITA Research and Development Laboratory

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