configure and asinl function problem
Sat Oct 8 20:12:00 GMT 2005
Joost Kraaijeveld wrote:
> On Sat, 2005-10-08 at 07:50 -0700, Tim Prince wrote:
>>such as the one used in the libstdc++ build itself. Maybe we should
>>look into how libstdc++ decides it can support asinl() on Cygwin. Did
> Actually asinl is a built-in functions provided by GCC, so I
> *think/hope* that it just is a matter of adding those functions to a
I've never seen trig functions "provided" by gcc; a very few math
built-ins are implemented for i386 (fabs, sqrt, et al., where it is
clear what needs to be done to support the various -march= options). gcc
has always followed the tradition of relying on someone else to provide
the C math library, and the corresponding headers.
To me, at least, the provision of a framework for defining built-in
functions is a separate question from actually "providing" them, in a
form ready to use.
Commonly used linux glibc headers tend to over-ride even the existing
limited built-in implementation, so gcc configure has to deal with that.
cygwin continues to get math functions from newlib, which supports
primarily platforms without long double.
I checked libstdc++ config.log, and it does determine that cygwin
supports no long double trig functions. As a result, libstdc++ is built
with _asinl() calling asin(). It would seem that a configure script
which comes to a different conclusion about cygwin math libraries than
the ones used by gcc must be broken.
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