extern "C" (C linkage) by default

Question

Question

Do GCC, MSVC, or Clang, or some combination support setting linkage to default to C?

Background

I have a large mixed C/C++ project, and while it's easy and logical to export symbols in the C++ sources with C linkage, those same sources are assuming the stuff in the rest of the project are under C++ linkage.

The current situation requires me to explicitly wrap anything the C sources use that is defined in the C++ sources and everything the C++ sources use from the C sources with extern "C++".

To top things off, I can't put extern "C" around entire source or header files, as the actual C++ stuff will then complain. (Such as from #include <memory> or templates I've defined.)

Answer 1

The standard pattern in a header file is:

#ifdef __cplusplus

// C++ stuff

extern "C" {
#endif

// C/C++ stuff

#ifdef __cplusplus
}
#endif

I'm not sure you've got any other options. The C/C++ stuff must be declared with C linkage everywhere. The C++-specific stuff must be declared with C++ linkage everywhere.

Answer 2

"C" linkage by default makes only sense for C sources, not for C++ sources, and vice versa. "C" linkage usually implies that names/symbols will not be mangled. "C" linkage is not expressive enough to be usable for C++ sources, e.g. for overloaded functions.