$ tree
.
|-- external.c
|-- sc.h
`-- serial_comm.cpp

$ cat external.c 
#include "sc.h"

int main() {
    struct MyStruct* sc;
    sc->myFunction1();
}

$ cat sc.h     
#ifndef SC_H
#define SC_H

struct MyStruct {
    int myVariable;
    void myFunction1();
    void myFunction2();
};

#endif

$ cat serial_comm.cpp 
#include <iostream>
#include "sc.h"

extern "C" void MyStruct::myFunction1() {
    std::cout << "Function 1 called" << std::endl;
}

extern "C" void MyStruct::myFunction2() {
    std::cout << "Function 2 called" << std::endl;
}

$ gcc external.c serial_comm.cpp -o my_program -lstdc++ -std=c++17
cc1: warning: command-line option '-std=c++17' is valid for C++/ObjC++ but not for C
In file included from external.c:1:
sc.h:6:10: error: field 'myFunction1' declared as a function
    6 |     void myFunction1();
      |          ^~~~~~~~~~~
sc.h:7:10: error: field 'myFunction2' declared as a function
    7 |     void myFunction2();
      |          ^~~~~~~~~~~

I have a project now that requires calling a C++17 structure’s function within C language. I expect to receive ‘Function 1 called’.

The error message I’m getting is as follows. How should I correct it? Thank you.