nuttx/Documentation/components/libs/libxx.rst

=====
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:

  .. code-block:: C

     void *operator new(std::size_t nbytes)

  .. code-block:: C

     void operator delete(void* ptr)

  .. code-block:: C

     void operator delete[](void *ptr)

  .. code-block:: C

     void __cxa_pure_virtual(void)

  .. code-block:: C

     int __aeabi_atexit(void* object, void (*destroyer)(void*), void *dso_handle)

  .. code-block:: C

     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