-fno-math-errno by default

[David Schultz]

On Sun, Feb 06, 2011, Gerald Pfeifer wrote:
> Pedro kindly made me aware of
> 
>   http://svn.freebsd.org/viewvc/base?view=revision&revision=181538
> 
> where David made -fno-math-errno the default for GCC with the following
> background:
> 
>   Our libm doesn't support the SysV mistake of setting errno, and never 
>   has.  This will need to be fixed upstream in a more generic way, but
>   the changes are somewhat more involved.
> 
> Do I understand correctly that libm on all versions of FreeBSD and on
> all platforms does not set errno, so this should become the default for
> FreeBSD also upstream?

That is correct.  Basically nobody sets errno in the math library
anymore, except for compatibility with old apps written for the
System V math library.  BSD never has and never will.  IEEE 754
floating point exception flags are much saner and faster.

> It would have been nice to report this upstream (and apologies if you
> did and it got missed) and I'll try to raise it there, but wanted to
> get confirmation first.

I submitted a change request to gcc about 2.5 years ago:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37073