[Bug math/22146] C++ build issue with float128 on x86_64

[romain.naour at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22146

--- Comment #8 from romain.naour at gmail dot com ---
Hi

Hi have a different error from the config.log. I'm using gcc 7.x (commit
56ce01906ecb0a3e04411f8ceb60b27f4877f070)

configure:18385: checking for obsolete isnan function in <math.h>
configure:18405: 
/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/./gcc/xgcc
-shared-libgcc
-B/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/./gcc
-nostdinc++
-L/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/x86_64-buildroot-linux-gnu/libstdc++-v3/src
-L/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/x86_64-buildroot-linux-gnu/libstdc++-v3/src/.libs
-L/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/x86_64-buildroot-linux-gnu/libstdc++-v3/libsupc++/.libs
-B/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/bin/
-B/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/lib/
-isystem
/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/include
-isystem
/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/sys-include
   -c -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -Os 
-D_GNU_SOURCE -std=c++11  conftest.cpp >&5
conftest.cpp:67:24: error: '::isnan' has not been declared
                using ::isnan;
                        ^~~~~
conftest.cpp:72:32: error: call of overloaded 'isnan(double)' is ambiguous
              bool b = isnan(0.0);
                                ^
conftest.cpp:68:21: note: candidate: bool std::isnan(float)
                bool isnan(float);
                     ^~~~~
conftest.cpp:69:21: note: candidate: bool std::isnan(long double)
                bool isnan(long double);
                     ^~~~~
configure:18405: $? = 1


Also, I don't have the error reported by Bernd:

configure:16625: checking for ISO C99 support in <math.h> for C++98
configure:16694: 
/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/./gcc/xgcc
-shared-libgcc
-B/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/./gcc
-nostdinc++
-L/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/x86_64-buildroot-linux-gnu/libstdc++-v3/src
-L/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/x86_64-buildroot-linux-gnu/libstdc++-v3/src/.libs
-L/home/kubu/toolchain/x86_64-glibc-master/build/host-gcc-final-custom/build/x86_64-buildroot-linux-gnu/libstdc++-v3/libsupc++/.libs
-B/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/bin/
-B/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/lib/
-isystem
/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/include
-isystem
/home/kubu/toolchain/x86_64-glibc-master/host/x86_64-buildroot-linux-gnu/sys-include
   -o conftest -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
 -Os  -D_GNU_SOURCE -std=c++98 -fno-exceptions   conftest.cpp  -lm >&5
configure:16694: $? = 0

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