Linkage between different C++ variants

The C++ language modes supported by the compiler fall into 3 groups:

• C++ V2 (Cfront C++)
• C++ V3
• C++ 2017, C++ 2020

Modules within a group can be linked together without any problems.

Modules from two different groups cannot be combined. If a function is defined in a module of one group and called in a module of another group, these functions are not linked to each other when binding. An open reference is created.

The modern C++ library for the language modes C++ 2017 and C++ 2020 is delivered in two versions. These versions are not compatible and are implemented in two different namespaces. A program can use only one version, a version mix is not possible.