[Go] interesting read of Eli Bendersky's "Does a concrete type implement an interface in Go?"

Eli Bendersky has post an interesting article titled
"Does a concrete type implement an interface in Go?"


I really do love seeing C++ experts playing with other languages from their deep understanding of C/C++/Assembly :-)


Go's interface stores embedded data's type information, RTTI in C++, a pointer to v-table minus offset is type information, plus offset are pointers to member functions(index honors declared sequence).

Go's interface stores embedded data act as this pointer in C++, while calling the member functions, copying the embedded data as first parameter into member functions.

Thus, if embedded data is pointer type, then copy the pointer into the member functions.

Alas, if embedded data is instance of the data type, then copy the instance into the member functions.

Go's interface implement:
https://github.com/golang/go/blob/56131cbd1d61ec446e10dfe72a96f329ed3d952a/src/go/types/type.go#L244

Thus, Go's interface type provides an extra layer of abstraction for interface exchanges.

Go: https://godbolt.org/z/U2WqDC

package main

import "fmt"

type fun struct {
}

func (f *fun) run() {
 fmt.Println("stateless member function call.")
}

type I interface {
 run()
}

func main() {
 I((*fun)(nil)).run()
}

C++: https://godbolt.org/z/YWAXze

#include <iostream>

struct fun {
    void run()
    {
        using std::cout;
        using std::endl;
        cout << "stateless member function call." << endl;
    }
};

int main()
{
    static_cast<fun*>(nullptr)->run();
}

Reference:
A book about the internals of the Go programming language
https://github.com/teh-cmc/go-internals

Go 1.1 Function Calls - Russ Cox, February 2013
https://docs.google.com/document/d/1bMwCey-gmqZVTpRax-ESeVuZGmjwbocYs1iHplK-cjo/pub

Go Data Structures: Interfaces, Russ Cox, December 1, 2009.
https://research.swtch.com/interfaces

Go Interfaces, Ian Lance Taylor
https://www.airs.com/blog/archives/277

[golang] reflection quick note
http://vsdmars.blogspot.com/2019/01/golang-reflection-quick-note.html