c++ - C++中的不同对象

Question

此程序使用构造函数在 C++ 中显示不同类型的对象。我附上了输出的快照。在输出中，为什么没有显示创建外部对象的消息？

//Program to illustrate different type of objects
#include<iostream.h>
#include<conio.h>
#include<string.h>
class diffobjs{
    public:
    char msg[10];
    diffobjs(char ar[]){
        strcpy(msg,ar);
        cout<<"\nObject created of type "<<msg;
    }
    ~diffobjs(){
        cout<<"\n"<<msg<<" object destroyed";
        getch();
    }
};
extern diffobjs d1("Global");
void main(){
    clrscr();
    diffobjs d2("Automatic");
    static diffobjs d3("Static");
    getch();
}

Answer 1

修复一些问题:

//Program to illustrate different type of objects

// Standard C++ headers have no .h
#include<iostream>

// Not portable
// #include<conio.h>

// This <string.h> and other C headers are replaced by c... headers
// #include<cstring>


class diffobjs{
    public:
    // Have a std std::string to avoid buffer overflows
    std::string msg;
    diffobjs(const std::string& s)
    //  Use initialization
    :   msg(s)
    {
        std::cout<<"Object created of type "<<msg<<'\n';
    }
    ~diffobjs() {
        std::cout<<msg<<" object destroyed"<<'\n';
    }
};

// A declaration would go in a header
extern diffobjs d1;

// The definition is without 'extern'
diffobjs d1("Global");

int main(){
    // Globals are initialized before main
    // Remove the non-portable clrscr();
    // clrscr();
    std::cout << "\n[Entering Main]\n\n";
    diffobjs d2("Automatic [1]");
    // A static in a function is initialized only once, the static has an impact on
    // the order of destruction.
    static diffobjs d3("Static");
    // Added
    diffobjs d4("Automatic [2]");
    // You might not see destruction, if you start the programm in your IDE
    // Hence, remove the non-portable getch()
    // getch();
    std::cout << "\n[Leaving Main]\n\n";
}