macOS C++ include and parse issues

[dmatter]

I'm getting compile problems in some C++ libraries I'm using from XCode.

For example:
'cmath' file not found
(for line #include <cmath> in file time.h from PCL)

And parse errors in Xcode/Contents/Developer/Toolchain/XcodeDefault.xctoolchain/usr/lib/c++/v1/cwchar
such as:
"No member names 'tm' in the global namespace.

Similar issues with ctime, string, etc

Any ideas how to fix these?
Thanks