Some language features are not supported. The restrictions regarding long long, alignment, unicode and the float format IEEE described in restrictions to ANSI/ISO C are also restrictions in C++.
Thread support
The C/C++ compiler does not support a specific thread package. In detail, this means that the headers <thread>, <mutex>, <shared_mutex>, <condition_variable> and <future> are not available. The Keyword thread_local leads to an error message in mode C++2017 or C++ 2020. The predefine __STDCPP_THREADS__ is not set.
Atomics
C/C++ 4.0 does not support the atomic types. Some of their usage has to have support in the thread library. Using the keywords associated with atomic types will give an error message. The header file <atomic> is not available.
C/C++ 4.0 does have support for some essential atomic features. Details are available on special request.
Header <execution>
The C/C++ compiler 4.0 does not support the header <execution>. The classes which should be declared in those headers are not supported.
Mathematical special functions
The mathematical special functions (C++ 2017 standard, chapter 29.9.5) are not supported. These are some advanced mathematical functions, for example Laguerre and Legendre.
Co-Routines
The co-routines from C++ 2020 are not supported. Use of the reserved words will lead to a specific warning.
Modules
The modules from C++ 2020 are not supported. The syntax will be recognized and will cause an error message.
Library of C++ 2020
The library of C++ 2020 is not supported. The library of C++ 2017 is available in language mode C++ 2020.