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

Reinstalling Xcode, command tools and homebrew, and

sudo rm -rf /usr/local/include

fixed this issue for me.