[RFC] Quad-float support in Fortran

[Joseph S. Myers]

On Thu, 28 Oct 2010, FX wrote:

> > * should avoid a shared libquad dependency unless the program actually 
> > uses the __float128 facilities.
> 
> I don't know how to do that. Unless we use a compiler flag, the driver 
> has no way of knowing whether the program uses __float128, does it?

The simplest way is using --as-needed (USE_LD_AS_NEEDED target macro and 
associated configure tests).  That depends on the program and the 
libgfortran.a objects it references only referencing libquadmath symbols 
if the functionality is needed.  If there are difficulties with that (e.g. 
for I/O) then use of weak symbols (as in the gthreads code) may be useful, 
so that the functionality is available when libquadmath is linked in but 
you can still link without it.

-- 
Joseph S. Myers
joseph@codesourcery.com