Re: [PATCH 6/8] float128: Expose _Float128 finite math functions.

[Joseph Myers <joseph at codesourcery dot com>]

On Fri, 3 Mar 2017, Gabriel F. T. Gomes wrote:

> On Wed, 9 Nov 2016 22:05:57 +0000
> Joseph Myers <joseph@codesourcery.com> wrote:
> 
> > Rather than a load of repetitive boilerplate, the function declarations 
> > here should be macroized, with only the definition of the macros depending 
> > on __USE_ISOC99, __MATH_DECLARE_LDOUBLE, __NO_LONG_DOUBLE_MATH and 
> > float128 presence etc. (for most functions, maybe obsolete and lgamma ones 
> > are more complicated).
> > 
> 
> My attempts to macroize the function declarations were a bit
> frustrating.  While some of the declarations follow a nice pattern
> (always declare for double; always declare for float when __USE_ISOC99;
> declare for long double based on __USE_ISOC99, __MATH_DECLARE_LDOUBLE,
> and __NO_LONG_DOUBLE_MATH), when that is not the case, the declarations
> are somewhat less clear and trickier to read, imo.

In subsequent discussions 
<https://sourceware.org/ml/libc-alpha/2017-01/msg00404.html> I suggested 
the right approach was like bits/mathcalls.h: make bits/math-finite.h into 
a header included once for each type, with different macros defined.  The 
inclusions for float and long double would be conditional on __USE_ISOC99 
(and the inclusions for _Float128 would be conditional on the same 
conditions under which bits/mathcalls.h is included for _Float128).

An alternative would be merging bits/math-finite.h into bits/mathcalls.h 
as I suggested in 
<https://sourceware.org/ml/libc-alpha/2016-11/msg01098.html>, but I think 
that would be more complicated to implement.

> For exp10 and pow10, the float version is declared *even* when
> __USE_ISOC99 is not. This means that I cannot create a macro that

That's because __USE_GNU implies __USE_ISOC99.  That also means that there 
is no change in semantics from making the inclusion for float conditional 
on __USE_ISOC99, as those float versions will still be declared exactly 
for __USE_GNU.

-- 
Joseph S. Myers
joseph@codesourcery.com