RFC: SH4 and the __fpscr_values object

[H. J. Lu]

On Tue, May 06, 2003 at 11:02:06PM -0400, Daniel Jacobowitz wrote:
> Due to the way that the SH4 FPU operates, we have to save two values for the
> control register (one for single precision and one for double precision) in
> a global state so that we can switch between single and double precision
> operation without losing changes to the fpscr state.  That's my memory of
> how it works, anyway.
> 
> What it boils down to is that any application which uses the FPU needs to
> have a copy of __fpscr_values, and it's important that there be exactly one
> copy in the application; including all loaded libraries.
> 
> For a while this was implemented by having it in crti.o; it's since moved to
> crt1.o (don't know exactly why).  The problem is that there's now an
> undefined reference in libm to __fpscr_values, and we build libm using -z
> defs.
> 
> So, any ideas on the right way to solve this problem?  Is there some reason
> I'm missing that it can't just be a normal variable in libc6?  That won't
> fix any libraries which build with -z defs but don't link to -lc, but I
> don't think there are many examples of that.
> 

Why not declare it extern weak and make sure it is exported dynamically
from crt1.o?


H.J.