Re: [Plplot-devel] Re: (potential) defect in libnn (libcsiro0)

[Rafael L. <rla...@us...>]

* Alan W. Irwin <ir...@be...> [2004-09-04 11:08]:

> On 2004-09-04 17:33+0200 Rafael Laboissiere wrote:
> 
> >* Alan W. Irwin <ir...@be...> [2004-09-03 14:28]:
> >
> >>Rafael, what test can we put into lib/nn/Makefile.am that gcc is being 
> >>used
> >>as the compiler at build time?
> >
> >AC_PROG_CC
> >if test "$GCC" = yes ; then
> >   AC_MSG_NOTICE([Cool, gcc is the C compiler])
> >fi
> >
> >(This is only an illustration.  AC_PROG_CC need not to go into
> >lib/nn/Makefile.am, since it appears already in configure.ac.)
> 
> The above logic will only work in configuration files processed by autoconf
> and will not work in Makefile.am files at all.  Is the above shorthand for
> the following scenario: we make the above test in one of the files in the cf
> directory and then set an automake conditional which in turn will be used in
> Makefile.am?  This, of course, means that the user won't be able to change
> CC between configuration and building, but I am not sure autotools allows
> such a compiler change in any case.
> 
> I have to say what I was asking for originally was a pure build-time test in
> the Makefile with $CC --version |grep gcc at the heart of the test, but it
> may be extremely difficult or impossible to make such a build-time test work
> cross-platform so I am willing to settle for the above configure-time logic.

We could put in configure.ac (or in a cf/*.ac file), after AC_PROG_CC:

    AM_CONDITIONAL(cc_is_gcc, [test "$GCC" = yes])

and in lib/nn/Makefile.am:

    if cc_is_gcc
        AM_CFLAGS = -O2 -fno-force-mem -ffloat-store
    endif

I did not test this extensively, but it should work.

-- 
Rafael