Re: compiling GSL on digital unix.

[Mark Galassi <rosalia at lanl dot gov>]

Hi Tim and Jon,

[Jon, tell me: what is amazon.com doing with GSL?  I'm fascinated!]

    Tim> I don't think there's an equivalent option in 2.7.2.x, so
    Tim> code compiled with that version of gcc (including libgsl)
    Tim> would not be fully IEEE compliant.

What is the downside to that?  Would you recommend that GSL not be
used in such a case?

I think it is a shame to have the code not build because of a bad
option: it looks cheesy.  I would prefer to have configure warn you
that the option is not there, and then either go on with a caveat, or
stop in a clean way.

Your note on gcc options for applications that *use* GSL is
interesting:

    Tim> On more note.  GSL's configure augments CFLAGS for either
    Tim> Linux or Digital Unix on the alpha because its configure.in
    Tim> authors know that to get fully compliant IEEE code some
    Tim> special options are required.  Packages that *use* GSL don't
    Tim> generally know that, though, and code that uses GSL on the
    Tim> alpha should be compiled using the same set of rounding and
    Tim> IEEE-related CFLAGS as GSL itself used.  This means that for
    Tim> packages that use GSL or software you write yourself that
    Tim> uses GSL, be sure you compile using the appropriate CFLAGS to
    Tim> enable soft-controlled rounding and IEEE compliant code.

I have been working on a "gsl-config" program (like gtk-config and
gnome-config) which would return the options needed to compile and
link with GSL.  This is important for various reasons, like the fact
that the libraries are installed into $(prefix)/gsl/libwhatever.a, so
you need a -L$(prefix)/gsl in the link line.

By the way, what's the worst that happens if -mieee is used to build
GSL but not the application that invokes GSL?