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> Obviously there is C++ which can leverage most of this too, but C++ traps you into an ABI which is difficult to use from any language which is not C++. To be

> Obviously there is C++ which can leverage most of this too, but C++ traps you into an ABI which is difficult to use from any language which is not C++. To be fair to C++, all the other languages in this space are as bad at providing ABIs in their own languages. All (almost?) mostly provide ways to declare C ABIs, which C++ also supports. C++ has rough C++ ABIs, but mostly because it bothers to try in the first place. It's not like other languages really "solved" ABI better than C++ has. Even C ABIs are a little rough since there's so much preprocessor use to factor in and/or avoid.

sparkie 3y ago
C's ABI is that much simpler because it doesn't really place any constraints on the memory layout of your types. With C++ (and others), the values passed around may also have vtables linked to them, so your language must then also provide an in-memory representation of objects which is compatible with the C++ representation in order to do FFI method calls. That places quite a constraint on your language because to do it efficiently you basically want a copy of the C++ object model. So you're developing a kind of C++ sibling language, and C++ is quite complex, and now any other languages which want to interoperate with yours has to do the same. This is why it's pretty standard to just have a C FFI and provide a C wrapper for C++ libraries to use them with other languages.
- jenadine 3y ago
  Of course the C ABI places constraints on the memory layout of the types. For example, alignment. Also in what register "small" types are passed when passing them to functions. It actually depends if the struct has float members or not. C itself is quite complex already. C++ adds more features. But for example, the Rust ABI uses the C++ ABI, because C is too simple and doesn't support unwinding (for panics) or 128bit integers

sparkie 3y ago

C's ABI is that much simpler because it doesn't really place any constraints on the memory layout of your types. With C++ (and others), the values passed around may also have vtables linked to them, so your language must then also provide an in-memory representation of objects which is compatible with the C++ representation in order to do FFI method calls. That places quite a constraint on your language because to do it efficiently you basically want a copy of the C++ object model. So you're developing a kind of C++ sibling language, and C++ is quite complex, and now any other languages which want to interoperate with yours has to do the same. This is why it's pretty standard to just have a C FFI and provide a C wrapper for C++ libraries to use them with other languages.

jenadine 3y ago
Of course the C ABI places constraints on the memory layout of the types. For example, alignment. Also in what register "small" types are passed when passing them to functions. It actually depends if the struct has float members or not. C itself is quite complex already. C++ adds more features. But for example, the Rust ABI uses the C++ ABI, because C is too simple and doesn't support unwinding (for panics) or 128bit integers