error: "undefined reference to" while compiling c++

Question

i'm working in a little c++ application, i'm trying to use xdotool (libxdo: https://github.com/jordansissel/xdotool ).

i builded xdotool using the "make" command, and put the libxdo.so and libxdo.so.3 into /usr/lib. and xdo.h into /usr/local/include.

im trying to compile my application using:

g++ -I /usr/local/include/ -L /usr/lib/ LinuxTest.cpp -lXtst -lX11 -lxdo

but im getting this error:

undefined reference to `xdo_new(char const*)'
undefined reference to `xdo_move_mouse_relative(xdo const*, int, int)'

this is my source code:

#include <iostream>
#include <X11/Xlib.h>
#include <X11/keysym.h>
#include <X11/X.h>
#include <unistd.h>
#include <X11/extensions/XTest.h>
#include <xdo.h>

using namespace std;

#define KEYCODE XK_Tab
int mapa[2048];
void hook();

xdo_t* xdoMain;

int main() {
    for (int i=0;i<2048;i++){
       mapa[i]=0;
    }
    xdoMain = xdo_new(NULL);
    xdo_move_mouse_relative(xdoMain,200,200);
    hook(); //do some things using X11
    return 0;
}

Have you run ldconfig after you put the lib into /usr/lib? — ott--
– ott--, Commented May 17, 2015 at 23:11

Loki Astari · Accepted Answer · 2015-05-17 23:13:12Z

2

I am guessing this is because xdo is a C library.
You are linking and building a C++ application.

Thus your compiler is thinking that xdo_new() is a C++ name mangled function. But in reality it has been linked into libxdo. as a C name mangled function.

I would try this:

extern "C" {
#include <xdo.h>
}

You are basically telling the compiler to treat all the names in xdo as C function declarations. As long as there are no classes this should work (if there are classes then my assumption is incorrect to start with).

answered May 17, 2015 at 23:13

Loki Astari

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2 Comments

moscoquera Over a year ago

thank you very much, I didn't know that XDO is a C library, besides that I'm not often c ++ programmer

Loki Astari Over a year ago

@moscoquera: If a library has new/free functions then it is probably is a C library, as C++ uses a technique called RAII that makes this redundant.

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