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Date: Sat, 9 Apr 2011 14:10:25 -0700
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Subject: Re: newlib and long-double question
From: "N. C." <necrocowmoo AT gmail DOT com>
To: cygwin AT cygwin DOT com
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On 4/9/11, marco atzeri <marco DOT atzeri AT gmail DOT com> wrote:
> On Sat, Apr 9, 2011 at 6:05 PM, Christopher Faylor  wrote:
>> On Sat, Apr 09, 2011 at 08:20:13AM -0700, Necro Cow wrote:
>>>Hello.
>>>
>>>I have recently discovered that the cygwin version I am using (1.7.7)
>>>doesn't support many long-double function, like sqrtl, modfl, frexpl,
>>>etc.
>>>
>>>I have been reading on newlib's website, sourceware.org/newlib, that
>>>as of version 1.18.0, such long-double functions are now supported.
>>>(http://sourceware.org/ml/newlib/2009/msg01135.html)
>
> further the newlib announce says:
> * long double math routines added for platforms where LDBL == DBL
>
> so in reality you gain no additional performance on the double.
>
>>>
>>>What I can't seem to find out is, what version of newlib is in the
>>>newest release of cygwin, and if it has this better support for
>>>long-double functions.
>>
>> Cygwin uses whatever is in the newlib tree as of its release date.  That
>> means that since Cygwin 1.7.7-1 was released in August 2010* it would
>> incorporate any newlib changes from 2009.  That doesn't mean that we would
>> export every single thing that newlib provides, however.  If functionality
>> is missing that means that no one has taken the time to get it working in
>> the Cygwin DLL.
>>
>> cgf
>>
>> *http://sourceware.org/ml/cygwin-announce/2010-08/msg00035.html
>>
>
> on 1.7.8 most of the missing "double" function were added
> http://sourceware.org/ml/cygwin-announce/2011-03/msg00000.html
>
> I thought to implement also the long double but as doubles are 64 bit
> and long doubles are just 80 bits on windows, I found the effort not worth.
>
> Marco

I have fully updated my cygwin tp 1.7.9(0.237/5/3) and I still get
this error when I try to build Perl (5.12.3 in this case but same with
other versions) with uselongdouble enabled in the Configure script,
which fails with:

*** You requested the use of long doubles but you do not seem to have
*** the following mathematical functions needed for long double support:
***     sqrtl modfl frexpl
*** Please rerun Configure without -Duselongdouble and/or -Dusemorebits.
*** Cannot continue, aborting.


On a Linux system that I have access to, I see that those functions
are in /lib/libm.* but cygwin's /lib/libm.* still seems to lack them.
Is there any work around or alternate version ofthis lib that actually
has these functions. I honestly do not mean to be rude, but how
difficult is it to impliment these functions which seem so common in
most unix-like systems? Or did nothing not get updated when I updated
cygwin?

Thanks,

M. C

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