Catalina C++: Using headers yield error: no member named 'signbit' in the global namespace

Question

After upgrading to Catalina from Mojave, Setuping: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk in the env.

I\

Answer 1

It is possible your copy of Xcode is corrupted. Check with codesign:

codesign --verify /Applications/Xcode.app

This happened to me, and the problem was corrupted Xcode. Reinstalling fixed it.

Something had modified the following:

file added: /Applications/Xcode-11.3.1-.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/json/__pycache__/scanner.cpython-37.pyc
file added: /Applications/Xcode-11.3.1-.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/json/__pycache__/decoder.cpython-37.pyc
file added: /Applications/Xcode-11.3.1-.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/json/__pycache__/encoder.cpython-37.pyc
file added: /Applications/Xcode-11.3.1-.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/json/__pycache__/__init__.cpython-37.pyc
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/DriverKit19.0.sdk/System/DriverKit/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/math.h
file modified: /Applications/Xcode-11.3.1-.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/math.h

math.h was empty in all the above places.