long double on ppc-darwin

[Geoff Keating]

On 17/12/2005, at 5:56 PM, Mike Stump wrote:

> On Dec 17, 2005, at 6:08 AM, FX Coudert wrote:
>
>> I'm trying to understand the gfortran failure  
>> large_real_kind_2.F90 on ppc-darwin7.9, which can be reduced to:
>>
>> $ cat large_real_kind_2.F90
>>   real(kind=16) :: x
>>   real(8) :: y
>>
>>   x = 1
>>   y = x
>>   x = cos (x)
>>   y = cos (y)
>>   print *, x, y, y-x
>>
>>   end
>> $ ./usr/local/gfortran/bin/gfortran -g large_real_kind_2.F90 && ./ 
>> a.out
>>   0.5403023058681397650104827000000        0.540302305868140        
>> 1.9841535727186827560257490000000E-0004
>>
>> But I can't make a C testcase for that. Is "long double" supposed  
>> to be usable on ppc-darwin7.9 ?
>>
>
> The trick is that things like sinl have a linker name like _sinl 
> $LDBL128.  This is to enable 8 byte long doubles to continue to  
> work, and _sin is an 8 byte long double routine.  Don't ask.   
> Binary compatibility is so very much fun.
>
> Since Geoff invented the scheme, I'm sure he had an idea of how he  
> thought it should work for Fortran.  My guess would be that gcc has  
> to pick the right library names internally for all languages, thus,  
> obviating the need for the asm () fun remap the names in C.

Yes; to do this right, GCC's builtins need to know about the  
different names.

If you're interested in fixing this, I can tell you what to do...
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