---
title: Using C++ in RIOT
description: This document explains how to use C++ in RIOT, including levels of support and requirements for C++ code.
---

# Levels of Support

A CPU in RIOT can have three levels of support for C++ code:

1. No support for C++ at all
2. C++ is supported, but no libstdc++ implementation is available
3. C++ is supported and a libstdc++ implementation is available

The reason for missing or only partial C++ support
can be one (or more) of the following:

- No libstdc++ implementation for the target platform is available to RIOT,
    or the official RIOT docker image is missing it
- Missing toolchain support for a given target platform
- The C++ toolchain requires library code
    (such as constructor guards for the thread safe initialization of statically
    allocated instances) or hooks in the startup process to perform initialization

# Using C++

In order for C++ code to compile with RIOT, the following needs to be done:

- All C++ files must have the file extension `.cpp`, all C++ headers `.hpp`
    - For external code, overwriting the make variable `SRCXXEXT`
        e.g. to `cxx` can be used to compile C++ files with other extensions,
        e.g. `.cxx`
- `FEATURES_REQUIRED += cpp` must be added to the applications `Makefile`
    - If additionally the libstdc++ is used,
        `FEATURES_REQUIRED += libstdcpp` must be set.

## RIOT Modules in C++

RIOT modules should be written in C, so that boards/platforms without
or partial C++ support can still use these modules.
However, external modules, packages and modules that require C++ support anyway
(e.g. the Arduino compatibility features) can be written in C++.
Also, some modules might be designed as compatibility layer for C++
or provide convenient access to RIOT-OS' features using C++ APIs.
These modules/packages have to depend on the `cpp` feature
(`FEATURES_REQUIRED += cpp`) and possibly the `libstdcpp` feature
using their `Makefile.dep`.

## See Also

Reference [C++ modules](https://doc.riot-os.org/group__cpp.html)
for a list of C++ modules.