HUGE_VALQ issue with cray compiler

[aminiussi]

Hi

The cmake quadmath detection code dectect quandmath availability with the de cray compiler:

10:40:20 [alainm@login3 rel]#crayCC --version
Cray clang version 18.0.0  (0e4696aa65fa9549bd5e19c216678cc98185b0f7)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/cray/pe/cce/18.0.0/cce-clang/x86_64/share/../bin
10:43:47 [alainm@login3 rel]#

10:39:59 [alainm@login3 rel]#more  znort.cpp 
#include <quadmath.h>                                                                                                                                              
int main()                                                                                                                                                         
{                                                                                                                                                                  
    __float128 f = -2.0Q;                                                                                                                                          
    f = fabsq(f);                                                                                                                                                  
                                                                                                                                                                   
    return 0;                                                                                                                                                      
}   
10:40:08 [alainm@login3 rel]#CC ./znort.cpp 
10:40:12 [alainm@login3 rel]#./a.out 
10:40:20 [alainm@login3 rel]#

Unfortuinatly, charconv uses HUGE_VALQ, which is not as available as expected:

10:45:42 [alainm@login3 rel]#ninja -j 1 -k 1
[0/2] Re-checking globbed directories...
[1/4] Building CXX object libs/charconv/CMakeFiles/boost_charconv.dir/src/from_chars.cpp.o
FAILED: libs/charconv/CMakeFiles/boost_charconv.dir/src/from_chars.cpp.o 
/opt/cray/pe/craype/2.7.32/bin/CC -DBOOST_CHARCONV_HAS_QUADMATH -DBOOST_CHARCONV_NO_LIB -DBOOST_CHARCONV_SOURCE -DBOOST_CHARCONV_STATIC_LINK -I/lus/work/CT4/cin7233/alainm/boost/libs/charconv/include -I/lus/work/CT4/cin7233/alainm/boost/libs/config/include -I/lus/work/CT4/cin7233/alainm/boost/libs/assert/include -I/lus/work/CT4/cin7233/alainm/boost/libs/core/include -I/lus/work/CT4/cin7233/alainm/boost/libs/static_assert/include -I/lus/work/CT4/cin7233/alainm/boost/libs/throw_exception/include -O3 -DNDEBUG -fvisibility=hidden -fvisibility-inlines-hidden -MD -MT libs/charconv/CMakeFiles/boost_charconv.dir/src/from_chars.cpp.o -MF libs/charconv/CMakeFiles/boost_charconv.dir/src/from_chars.cpp.o.d -o libs/charconv/CMakeFiles/boost_charconv.dir/src/from_chars.cpp.o -c /lus/work/CT4/cin7233/alainm/boost/libs/charconv/src/from_chars.cpp
In file included from /lus/work/CT4/cin7233/alainm/boost/libs/charconv/src/from_chars.cpp:14:
/lus/work/CT4/cin7233/alainm/boost/libs/charconv/src/float128_impl.hpp:146:28: error: use of undeclared identifier '__builtin_huge_valq'
  146 |         return negative ? -HUGE_VALQ : HUGE_VALQ;
      |                            ^
/opt/cray/pe/cce/18.0.0/cce/x86_64/include/craylibs/quadmath.h:163:19: note: expanded from macro 'HUGE_VALQ'
  163 | #define HUGE_VALQ __builtin_huge_valq()
      |                  

So that looks like a cray specific issue, but would it be worth checking for HUGE_VALQ availability in the quadmath detection test?
As in:

    __float128 big = -HUGE_VALQ;                                                                                                                                          

?

thanks