libxx
This directory contains three C++ library:
- A fragmentary C++ library that will allow to build only the simplest of C++ applications. In the deeply embedded world, that is probably all that is necessary. - At present, only the following are supported here: - void *operator new(std::size_t nbytes) - void operator delete(void* ptr) - void operator delete[](void *ptr) - void __cxa_pure_virtual(void) - int __aeabi_atexit(void* object, void (*destroyer)(void*), void *dso_handle) - int __cxa_atexit(__cxa_exitfunc_t func, FAR void *arg, FAR void *dso_handle) - This implementation is selected when neither of the following two options are enabled. 
- LLVM “libc++” C++ library (http://libcxx.llvm.org/) This implementation is selected with CONFIG_LIBCXX=y. 
- uClibc++ C++ library (http://cxx.uclibc.org/) This implementation is selected with CONFIG_UCLIBCXX=y. 
operator new
This operator should take a type of size_t.  But size_t has an unknown underlying
type.  In the nuttx sys/types.h header file, size_t is typed as uint32_t
(which is determined by architecture-specific logic).  But the C++
compiler may believe that size_t is of a different type resulting in
compilation errors in the operator.  Using the underlying integer type
instead of size_t seems to resolve the compilation issues. Need to
REVISIT this.
Once some C++ compilers, this will cause an error:
Problem:     "'operator new' takes size_t ('...') as first parameter"
Workaround:  Add -fpermissive to the compilation flags