MacOS环境，C++项目include ＜cmath＞编译时产生错误：error: no member named ‘*****‘ in the global namespace

1.问题描述

自从升级macOS Monterey 版本12.6.3 (21G419)后（XCode、CommandLineTools也一并升级了）。C++项目编译时，出现如下类似问题：

[  0%] Building CXX object OgreMain/CMakeFiles/OgreMain.dir/src/OgreASTCCodec.cpp.o
		cd /Users/roman/Downloads/ogre-1.12.2/build/OgreMain && /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++  -DOgreMain_EXPORTS -D__ASSERT_MACROS_DEFINE_VERSIONS_WITHOUT_UNDERSCORES=0 -I/Users/roman/Downloads/ogre-1.12.2/OgreMain/src/OSX -I/Users/roman/Downloads/ogre-1.12.2/OgreMain/include/Threading -I/Users/roman/Downloads/ogre-1.12.2/OgreMain/src -I/Users/roman/Downloads/ogre-1.12.2/build/Dependencies/include -I/Users/roman/Downloads/ogre-1.12.2/OgreMain/include -I/Users/roman/Downloads/ogre-1.12.2/build/include -I/Users/roman/Downloads/ogre-1.12.2/OgreMain -isystem /usr/local/include  -Wall -Winit-self -Wcast-qual -Wwrite-strings -Wextra -Wundef -Wmissing-declarations -Wno-unused-parameter -Wshadow -Wno-missing-field-initializers -Wno-long-long -Wno-inconsistent-missing-override  -msse -O3 -DNDEBUG -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -fPIC -fvisibility=hidden -fvisibility-inlines-hidden   -std=c++11 -o CMakeFiles/OgreMain.dir/src/OgreASTCCodec.cpp.o -c /Users/roman/Downloads/ogre-1.12.2/OgreMain/src/OgreASTCCodec.cpp
		In file included from /Users/roman/Downloads/ogre-1.12.2/OgreMain/src/OgreASTCCodec.cpp:29:
		In file included from /Users/roman/Downloads/ogre-1.12.2/OgreMain/src/OgreStableHeaders.h:40:
		In file included from /Users/roman/Downloads/ogre-1.12.2/OgreMain/include/OgrePrerequisites.h:309:
		In file included from /Users/roman/Downloads/ogre-1.12.2/OgreMain/include/OgreStdHeaders.h:10:
		/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:314:9: error: no member named 'signbit' in the global namespace
		using ::signbit;
			  ~~^
		/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:315:9: error: no member named 'fpclassify' in the global namespace
		using ::fpclassify;
			  ~~^
		/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:316:9: error: no member named 'isfinite' in the global namespace; did you mean 'finite'?
		using ::isfinite;

2.解决方法

通过重装XCode、CommandLineTools都无法解决，折腾了好几天，实在很抓狂。

原因就是include<math.h>时找不到math.h，可能是升级了macOS、XCode或CommandLineTools导致的。

最后，通过参考网上论坛后，采用了一种简单粗暴的方式解决的上述问题。方法描述如下：

打开报错的cmath文件；
在cmath中将include<math.h>替换为：

#include</Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/math.h>

或者

#include </Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/math.h>

如果，在/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/math.h中include_next <math.h>也出现上述问题，则将其直接设定为：

#include_next </Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/math.h>

如果，还有其他文件include也出现该问题，则也可采用类似方法解决。

导致上述问题的原因实在不知，若大家有其他更好的解决方案，请留言。万分感谢！

MacOS环境，C++项目include ＜cmath＞编译时产生错误：error: no member named ‘*****‘ in the global namespace

1.问题描述

2.解决方法

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