qt开发环境

#include <QCoreApplication>#include <iostream>using namespace std;#define unused(a) a=avoid foo(void){    cout << 1 << endl;}void foo(int n){    unused(n);    cout << 2 << endl;}void foo(int* p){    unused(p);    cout << 3 <<endl;}int foo(double x){    unused(x);    cout << 4 << endl;    return 0;}char const* foo(double x ,int y){    unused(x);unused(y);    cout << 5 << endl;    return NULL;}char const* foo(int x, double y){    unused(x);unused(y);    cout << 6 << endl;    return NULL;}void bar(char a){    unused(a);    cout << 'A' << endl;}void bar(int a){    unused(a);    cout << 'B' << endl;}void bar(long long a){    unused(a);    cout << 'C' << endl;}void hum(char* p, int n){    unused(p);unused(n);    cout << "aa" << endl;}void hum(char const* p, char n){    unused(p);unused(n);    cout << "bb" << endl;}int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    int n;    double d = 0;    //函数名字相同，参数表不同，构成重载，重载和返回值、参数名、相同类型的引用和非引用也不构成重载    //根据参数表类型来寻找寒素    foo();//1    foo(n);//2    foo(&n);//3    foo(d);//4    foo(n,d);//6    foo(d,n);//5    //如果不是像前面那样完美匹配，编译器会选择最安全的那个，工作量最小的    short m = 0;    bar(m);//B    //被警告，编译器说这俩都不好，它选择的第二个，第二个更安全，不需要扩展内存    char* p = NULL;    char u = 0;    hum(p, u);    //作用域，名字空间嵌套，最近的     return a.exec();}