'isnan' was not declared in this scope if (isnan(t)) ；这样的问题怎么解决?

[changtj]

H:\vcpkg\downloads\log4z-master\g++>cmake -Dlog4z_SOURCE_DIR=".." -G "MinGW Makefiles"
CMake Error: Error: generator : MinGW Makefiles
Does not match the generator used previously: Visual Studio 15 2017
Either remove the CMakeCache.txt file and CMakeFiles directory or choose a different binary directory.

H:\vcpkg\downloads\log4z-master\g++>cmake -Dlog4z_SOURCE_DIR=".." -G "MinGW Makefiles"
-- The C compiler identification is GNU 5.3.0
-- The CXX compiler identification is GNU 5.3.0
-- Check for working C compiler: C:/Qt/Qt5.9.2/Tools/mingw530_32/bin/gcc.exe
-- Check for working C compiler: C:/Qt/Qt5.9.2/Tools/mingw530_32/bin/gcc.exe -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: C:/Qt/Qt5.9.2/Tools/mingw530_32/bin/g++.exe
-- Check for working CXX compiler: C:/Qt/Qt5.9.2/Tools/mingw530_32/bin/g++.exe -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: H:/vcpkg/downloads/log4z-master/g++

H:\vcpkg\downloads\log4z-master\g++>mingw32-make
Scanning dependencies of target log4z
[ 50%] Building CXX object CMakeFiles/log4z.dir/H_/vcpkg/downloads/log4z-master/log4z.cpp.obj
In file included from H:\vcpkg\downloads\log4z-master\log4z.cpp:37:0:
H:\vcpkg\downloads\log4z-master\log4z.h: In member function 'zsummer::log4z::Log4zStream& zsummer::log4z::Log4zStream::writeDouble(double, bool)':
H:\vcpkg\downloads\log4z-master\log4z.h:810:16: error: 'isnan' was not declared in this scope
if (isnan(t))
^
H:\vcpkg\downloads\log4z-master\log4z.h:810:16: note: suggested alternative:
In file included from H:\vcpkg\downloads\log4z-master\log4z.h:193:0,
from H:\vcpkg\downloads\log4z-master\log4z.cpp:37:
C:/Qt/Qt5.9.2/Tools/mingw530_32/i686-w64-mingw32/include/c++/cmath:862:5: note: 'std::isnan'
isnan(_Tp __f)
^
In file included from H:\vcpkg\downloads\log4z-master\log4z.cpp:37:0:
H:\vcpkg\downloads\log4z-master\log4z.h:815:21: error: 'isinf' was not declared in this scope
else if (isinf(t))
^
H:\vcpkg\downloads\log4z-master\log4z.h:815:21: note: suggested alternative:
In file included from H:\vcpkg\downloads\log4z-master\log4z.h:193:0,
from H:\vcpkg\downloads\log4z-master\log4z.cpp:37:
C:/Qt/Qt5.9.2/Tools/mingw530_32/i686-w64-mingw32/include/c++/cmath:853:5: note: 'std::isinf'
isinf(_Tp __f)
^
H:\vcpkg\downloads\log4z-master\log4z.cpp: In member function 'virtual zsummer::log4z::LogData* zsummer::log4z::LogerManager::makeLogData(LoggerId, int)':
H:\vcpkg\downloads\log4z-master\log4z.cpp:1262:38: warning: 'thread' attribute directive ignored [-Wattributes]
static __declspec(thread) tm g_tt = { 0 };
^
H:\vcpkg\downloads\log4z-master\log4z.cpp:1263:42: warning: 'thread' attribute directive ignored [-Wattributes]
static declspec(thread) time_t g_curDayTime = 0 ;
^
CMakeFiles\log4z.dir\build.make:61: recipe for target 'CMakeFiles/log4z.dir/H/vcpkg/downloads/log4z-master/log4z.cpp.obj' failed
mingw32-make[2]: *** [CMakeFiles/log4z.dir/H/vcpkg/downloads/log4z-master/log4z.cpp.obj] Error 1
CMakeFiles\Makefile2:66: recipe for target 'CMakeFiles/log4z.dir/all' failed
mingw32-make[1]: *** [CMakeFiles/log4z.dir/all] Error 2
Makefile:128: recipe for target 'all' failed
mingw32-make: *** [all] Error 2

H:\vcpkg\downloads\log4z-master\g++>g++
g++: fatal error: no input files
compilation terminated.

H:\vcpkg\downloads\log4z-master\g++>mingw32-make -version
GNU Make 4.1
Built for i686-w64-mingw32
Copyright (C) 1988-2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later http://gnu.org/licenses/gpl.html
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

H:\vcpkg\downloads\log4z-master\g++>

[vrqq]

试试在前面加上std:: 变成std::isnan std::isinf

然后打一下__cpluscplus看看是不是这个原因