[SUGGESTION] cppfront transpiler parameter to generate interoperability with C

[raffaeler]

My suggestion does not touch cppfront at all, but is a transpiler parameter to automatically generate extern C functions to overcome the binary compatibility issues in C++.

The goal is to allow consuming C++ pure libraries from other languages without messing with the mangled names and risking breaking changes with future versions of the C++ libraries and/or compilers.

The generation should be restricted to:

• global or public member functions tagged by the user so that the generation is limited
• global or public member functions taking and returning basic types
• mapping the ctor/dtor to create/close functions taking care of allocating/freeing objects

If I understood correctly, cppfront makes the parameter direction clear using in and out. This metadata can be used to apply the patterns to correctly allocate/deallocate the memory for the parameters.

It could be also useful to define a "type transformer" that can be used by the transpiler to extend the types that can be used in the generation. For example, a std::vector<T> could be mapped to T* and length.

[JohelEGP]

The generation should be restricted to:

Sounds like a prime use-case for metafunctions.
E.g.,

algo: @c_api (r: std::span<int>) = { … }

could generate the usual Cpp2 declaration, and a Cpp1 extern "C" at lower time that looks like:

extern "C" {
void algo(int* rp, std::size_t rs) { algo(std::span<int>{rp, rs}); }
}

[raffaeler]

@JohelEGP sounds neat :)