C ++在Xcode控制台中未显示cout，但在Terminal中可完美运行

Question

Basically i am running a simple program in Xcode Version 8.3 (8E162)

#include <iostream>
using namespace std;
int main() {
    int a;   
    cout << "What is your age: ";
    cin >> a;
    cout << "My age is " << a << endl;
    return 0;
}

I have seen different questions about cout need to be flushed and all std::cout won't print and Xcode debugger not showing C++ cout output . The Xcode debugger does not print cout until i put \\n or endl . But, it works perfectly fine on terminal.

What if i had to use What is your age: and the user input age in the single line rather than the next line putting \\n and endl ?

This is what the Xcode debugger shows after build and run

This is when user inputs and it displays the result

This is on the terminal and this is what exactly what i need the output on the Xcode debugger.

Answer 1

By doing some research, there seems to be bug on cin and cout stream on Xcode Version 8.3 Build 8E162 released on Mar 27, 2017 . Degrading to Xcode Version 8.2.1 works like a charm.

Answer 2

You already solved your problem yourself: std::cout uses buffered output and should always be flushed. You can achieve this by either using std::cout << "What is your age? << std::flush , by using std::cout.flush() or by adding a line break like std::endl which flushes implicitly.

A complete solution could look like this:

#include <iostream>

using namespace std;

int main() {
    int a;   
    cout << "What is your age: " << flush;
    cin >> a;
    cout << "My age is " << a << endl;
    return 0;
}