Cygwin Perl and -Duselongdouble

[Sisyphus]

Hi,
I'd like to have a perl on Cygwin built with -Duselongdouble, so I tried 
building blead (5.9.5) from source with:

./configure -de -Dusemorebits -Dprefix=~/Rob -Dusethreads -Uusemymalloc -Doptimize=-O3 
 -Dusedevel

but that failed, culminating as follows:

----------------------------
.
.
sqrtl() NOT found.

scalbnl() NOT found.

modfl() NOT found.

modfl() prototype NOT found.

*** 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.
----------------------------

I haven't checked for 'modfl' and 'frexpl', but 'sqrtl' at least seems to be 
available in the C compiler. Why does configure report that it's not 
available ? (I don't need a detailed account ... rather I'm just seeking 
confirmation that the error is valid and well founded :-)

By way of explanation, I find that perls built with -Duse64bitint but 
not -Duselongdouble don't DWIM very well. For example (with my current 
Cygwin build of perl 5.8.7 built with -Duse64bit int):

-----------------------------
Rob@desktop2 ~/comp/perl-5.9.5
$ perl -e 'print "Crap" if 2 ** 55 + 6 == 2 ** 55 + 7'
Crap
Rob@desktop2 ~/comp/perl-5.9.5
-----------------------------

As I understand it, that's typical of *all* perls built with -Duse64bitint 
but not -Duselongdouble, not just Cygwin. (Build with -Duselongdouble as 
well and it doesn't print "Crap" ... on linux, at least.)

Cheers,
Rob 


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