[OE-core] [PATCH 8/8] boost: Fix build on soft-float ABI arm systems

[Phil Blundell]

On Wed, 2016-02-03 at 12:58 -0800, Khem Raj wrote:
> On Wed, Feb 3, 2016 at 12:42 PM, Phil Blundell <pb at pbcl.net> wrote:
>   I think it might be true
> > that some libraries don't implement fesetenv() when using softfp (i.e.
> > no VFP instructions at all) but that is not necessarily the same thing
> > as the soft float ABI.
> 
> does glibc implement it correctly using soft-fp ? my tests failed for
> glibc thats why
> I used the VFP detection logic

It depends what you mean by "correctly".  If you don't have a VFP unit
then fesetenv() will fail (return nonzero) but the symbols will be
available and there should be no error at build time.  If you do have a
VFP unit and are using it then, irrespective of your ABI, fesetenv()
should succeed and subsequent operations ought to behave correctly.

I think there is a possible hole in the case where you do have a VFP
unit available but have compiled your code -msoft-float, have not
installed a VFP optimized library, and hence are not actually using the
VFP.  In this situation, yes, I think it's quite conceivable that glibc
might be doing the wrong thing.  Fortunately I think this scenario is
rare enough that we probably don't need to worry about it too much.

p.