Re: [MIT-Scheme-devel] Ubuntu 11.04 and FE_DFL_ENV.

[Taylor R Campbell]

   Date: Thu, 16 Jun 2011 10:11:28 -0700
   From: Matt Birkholz <address@hidden>

   So obviously a less borked fix would be to adjust FP_CONTROL_WORD for
   glibc on i386 and x86-64.  But doesn't our shiny new floenv.scm takes
   care of all this, withOUT going behind libc's back?  Can we punt the
   ancient fpu inits in microcode/cmpauxmd/i386.m4 and x86-64.m4?  (Dare
   me to try it?)

Maybe.  I'm not sure in what floating-point environment a restored
band would start up if we removed the setting of the control word in
the assembly hooks.  I'd suggest masking all exceptions there, and
then going through every entry point into a restored band (and the
cold load) to make sure it sets up the floating-point environment
appropriately.  (And I have no idea what happens with Windows.)

Perhaps Scheme ought to expose the x86 denormalized exception (with a
null implementation for all the other machines we support -- er, uh,
yeah), but I'm pretty sure it shouldn't be trapped by default.
There's also a flush-to-zero control bit that we might want to expose
somehow.

   It's Unity, isn't it?  You can't stand Unity?  I gave it up after a
   couple weeks -- went back to Ubuntu Classic.  Maybe I should go back
   to Debian!

No, it's more that I can't fit Ubuntu into my head, whereas I can fit
NetBSD into my head, and NetBSD is much easier to fix when it's
broken.