cpp-target.md

C++ Target

• Call stack debug information: Source function names may be a little different even when debugging a .
  • I'm not sure a stack of debug information is safe as it can get incorrect after the exception is handled and program resumes using that same information stack.
• Generated structure names: dot is replaced by :: (and thus defined in C++ namespaces) and special characters turn into _. The [FFI] decorator may be used in some form for custom names.
  • Certain objects won't generate structure and rather re-use one from C++ side. This will be the case for Object maybe.
• Object in the any type context (*) may also be used to represent undefined or null. They are not treated as objects; this is just a variant representation.
• Needed structures will be defined multiple times; for example:
  • Empty: class C1 : Object; class C2 : Object;
    • Sort these empty structures based on inherited class. The basemost class appears first as an empty structure.
  • Then fields and method signatures: class C1 : Object { ... }; class C2 : Object { ... };
    • If a field has a constant initial value and it's possible to express it in C++, generate an initialiser for it.
  • Then implementation: class C1 : Object { ... }; class C2 : Object { ... };
    • If a field has both a constant initial value, no initialiser and it was possible to express its constant initial value in C++, don't generate an assignment for it in the constructor.

Exceptions

• To get call stack, use libunwind: https://www.nongnu.org/libunwind/man/libunwind(3).html

#include <cassert>
#include <exception>

class MyCustomException : public std::exception {
    public:
    char* what () {
        return "Message plus stacktrace";
    }
};

namespace com::q {
    struct C {
        #line 404 "index.vs"
        static void f(int i) {
            assert(false);
            // C++ prrogram doesn't format the thrown error,
            // so no message nor callstack.
            // so every entry, including asynchronous functions,
            // have to catch any Error object from VioletScript
            // and panic, displaying its what() properly.
            throw MyCustomException();
        }
    };
}

int main() {
#line 777 "index.vs"
    com::q::C::f(0);
}

Name Clash

• Things starting with like com:: go fine; others may need some prefix or suffix.
• Names that are reserved words in C++ (like for) need some prefix or suffix too.