C++ Language Support

C++ is a general-purpose object-oriented programming language that is based on the C language.

Enabling C++ Support

Zephyr supports applications written in both C and C++. However, to use C++ in an application you must configure Zephyr to include C++ support by selecting the CONFIG_CPP in the application configuration file.

To enable C++ support, the compiler toolchain must also include a C++ compiler and the included compiler must be supported by the Zephyr build system. The Zephyr SDK, which includes the GNU C++ Compiler (part of GCC), is supported by Zephyr, and the features and their availability documented here assume the use of the Zephyr SDK.

The default C++ standard level (i.e. the language enforced by the compiler flags passed) for Zephyr apps is C++11. Other standards are available via kconfig choice, for example CONFIG_STD_CPP98. The oldest standard supported and tested in Zephyr is C++98.

When compiling a source file, the build system selects the C++ compiler based on the suffix (extension) of the files. Files identified with either a cpp or a cxx suffix are compiled using the C++ compiler. For example, myCplusplusApp.cpp is compiled using C++.

The C++ standard requires the main() function to have the return type of int. Your main() must be defined as int main(void). Zephyr ignores the return value from main, so applications should not return status information and should, instead, return zero.


Do not use C++ for kernel, driver, or system initialization code.

Language Features

Zephyr currently provides only a subset of C++ functionality. The following features are not supported:

  • Static global object destruction

  • OS-specific C++ standard library classes (e.g. std::thread, std::mutex)

While not an exhaustive list, support for the following functionality is included:

  • Inheritance

  • Virtual functions

  • Virtual tables

  • Static global object constructors

  • Dynamic object management with the new and delete operators

  • Exceptions

  • RTTI

  • Standard Template Library (STL)

Static global object constructors are initialized after the drivers are initialized but before the application main() function. Therefore, use of C++ is restricted to application code.

In order to make use of the C++ exceptions, the CONFIG_CPP_EXCEPTIONS must be selected in the application configuration file.

Zephyr Minimal C++ Library

Zephyr minimal C++ library (lib/cpp/minimal) provides a minimal subset of the C++ standard library and application binary interface (ABI) functions to enable basic C++ language support. This includes:

  • new and delete operators

  • virtual function stub and vtables

  • static global initializers for global constructors

The scope of the minimal C++ library is strictly limited to providing the basic C++ language support, and it does not implement any Standard Template Library (STL) classes and functions. For this reason, it is only suitable for use in the applications that implement their own (non-standard) class library and do not rely on the Standard Template Library (STL) components.

Any application that makes use of the Standard Template Library (STL) components, such as std::string and std::vector, must enable the C++ standard library support.

C++ Standard Library

The C++ Standard Library is a collection of classes and functions that are part of the ISO C++ standard (std namespace).

Zephyr does not include any C++ standard library implementation in source code form. Instead, it allows configuring the build system to link against the pre-built C++ standard library included in the C++ compiler toolchain.

To enable C++ standard library, select an applicable toolchain-specific C++ standard library type from the CONFIG_LIBCPP_IMPLEMENTATION in the application configuration file.

For instance, when building with the Zephyr SDK, the build system can be configured to link against the GNU C++ Library (libstdc++.a), which is a fully featured C++ standard library that provides all features required by the ISO C++ standard including the Standard Template Library (STL), by selecting CONFIG_GLIBCXX_LIBCPP in the application configuration file.

The following C++ standard libraries are supported by Zephyr:

A Zephyr subsystem that requires the features from the full C++ standard library can select, from its config, CONFIG_REQUIRES_FULL_LIBCPP, which automatically selects a compatible C++ standard library unless the Kconfig symbol for a specific C++ standard library is selected.