Qt Creator XOpenDisplay undefined reference

Question

Now I am feeling quite stupid. I am trying to do some stuff with xlib in Qt Creator.

My code:

#include <QtCore/QCoreApplication>
#include <X11/Xlib.h>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    Display *display = XOpenDisplay(NULL);

    return 0;
}

Just one line of code and gives me:

/main.cpp:8: undefined reference to `XOpenDisplay'

It is defined in Xlib.h as

extern Display *XOpenDisplay(
    _Xconst char* /* display_name */
);

I feel I am missing something very basic.

Answer 1

Found it... compiler problem

added -lX11 to the make file