On Mon, 23 Mar 2009, Rolf Grossmann wrote:
> Andy Dougherty wrote:
> > > > #include <math.h>
> > > > #if defined(__GNUC__) && defined(_LIB_VERSION)
> > > > _LIB_VERSION_TYPE _LIB_VERSION = _IEEE_;
> > > > #endif
> > > >
> > > > Maybe _LIB_VERSION is not defined?
> >
> > It is not solved by that bit of code. At least on Solaris 8, _LIB_VERSION
> > is not defined. Nor is _LIB_VERSION_TYPE. That bit of code is just
> > irrelevant. It has never been useful there. It was worth trying, but it
> > doesn't do anything.
>
> But that bit of code might be the hint we're looking for. In my math.h on
> Solaris 10 there are these definitions:
>
> enum version {libm_ieee = -1, c_issue_4, ansi_1, strict_ansi};
> extern const enum version _lib_version;
>
> wrapped in
>
> #if defined(__EXTENSIONS__) || !defined(_XOPEN_SOURCE)
>
> So I've verified that Solaris cc has a method of either setting or
> linking against a correct constant for _lib_version with -xlibmieee.
> Unfortunately it really is constant, so trying to trick it just results
> in a segfault :( A quick Google search didn't give me any hints either
> and I haven't had the time to dig deeper, yet.
On Solaris 8, here's how it seems to work: The value of libm_ieee can
have one of those four values you quote above. Those values are set in
the object files /usr/ccs/lib/values-X*.o. On my system, there are
five such files:
File _lib_version atan2(-0.0, -0.0) Purpose
values-Xa.o 1 0 ANSI + K&R extensions
values-Xc.o 2 0 strict conformant ANSI
values-Xs.o 0 0 (DOMAIN error) K&R only
values-Xt.o 0 0 (DOMAIN error) K&R + ANSI transitional
values-xpg4.o -1 -3.14159 XPG4 compliance
(These files are mostly named after corresponding cc(1) flags; for
example cc -Xc gives strict ANSI conformance.)
Further, if you have installed Sun's compiler, there is an additional
files values-xi.o under /opt/SUNWspro/
values-xi.o -1 -3.14159 IEEE-754 compliance
What the -xlibmieee flag does for Sun's compiler is have the linker
replace values-Xa.o by values-xi.
For gcc, the file values-Xa.o appears to be hard-wired in to the
built-in specs. The only way to change it appears to be to override it
with a custom specs file. Hmm. That might not be too hard. We just
create a file (I'll call it 'parrot-gcc.specs') with the following two
lines:
*startfile_arch:
%{ansi:values-Xc.o%s} %{!ansi:values-xpg4.o%s}
and then add -specs=parrot-gcc.specs to $linkflags.
(if values-xi.o is available, that might be a better choice.)
It's not *too* messy. What do you think? (Hmm. It might get messy
for installation, however -- where do we put the specs file so that
languages that build against parrot know how to pick it up?)
--
Andy Dougherty [email protected]
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