Question

I am quite new to linux development, and having trouble using a class from a separate file in my main. The error I am getting when making (after having created makefile with cmake) is that system does not name a type, I think the code in system class is correct as if I compile without attempting to create an object of the system class I have no errors, so I think it may be to do with the way I have written the CMakeLists.txt file.

This is my CMakeLists file:

    cmake_minimum_required (VERSION 2.6)
    project (GL_PROJECT)

    add_library(system system.cpp)

    include_directories(${GL_PROJECT_SOURCE_DIR})
    link_directories(${GL_PROJECT_BINARY_DIR})

      find_package(X11)

      if(NOT X11_FOUND)
        message(FATAL_ERROR "Failed to find X11")
      endif(NOT X11_FOUND)

       find_package(OpenGL)
      if(NOT OPENGL_FOUND)
        message(FATAL_ERROR "Failed to find opengl")
      endif(NOT OPENGL_FOUND)

    set(CORELIBS ${OPENGL_LIBRARY} ${X11_LIBRARY})

    add_executable(mainEx main.cpp system.cpp)

    target_link_libraries(mainEx ${CORELIBS} system)

I have in the source directory my main.cpp, system.h (class definition) and system.cpp (class implementation)

In main:

      #include"system.h"


      system sys;

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

      while(1) 
        {
            sys.Run();
        }

      }

X11 and GL includes etc are in system.h, I think the code in there is correct and not causing the error (as it builds fine if i dont try and create an instance of the class). I have omitted the actual header and implementation for brevity in the hope that it will be an obvious error in the CMakeList file, but if necessary I can add these too?

Any ideas?

Thanks in advance.

EDIT: Here are the errors in terminal

    [tims@localhost build]$ make
    Scanning dependencies of target system
    [ 33%] Building CXX object CMakeFiles/system.dir/system.cpp.o
    Linking CXX static library libsystem.a
    [ 33%] Built target system
    Scanning dependencies of target mainEx
    [ 66%] Building CXX object CMakeFiles/mainEx.dir/main.cpp.o
    /home/tims/Code/GL_Project/main.cpp:5:1: error: ‘system’ does not name a type
    /home/tims/Code/GL_Project/main.cpp: In function ‘int main(int, char**)’:
    /home/tims/Code/GL_Project/main.cpp:11:3: error: ‘sys’ was not declared in this scope
    make[2]: *** [CMakeFiles/mainEx.dir/main.cpp.o] Error 1
    make[1]: *** [CMakeFiles/mainEx.dir/all] Error 2
    make: *** [all] Error 2

Edit 2: system.h

    #include<stdio.h>
    #include<stdlib.h>
    #include<X11/X.h>
    #include<X11/Xlib.h>
    #include <GL/gl.h>           
    #include <GL/glx.h>                                                                
    #include <GL/glu.h>    

    class system {
    public:
        system(void);

        ~system(void);

        void CreateGLXWindow();

        void Run();

        //Contains information about X server we will be communicating with 
        Display *display;

    XEvent xEvent;

    //Window instance
    Window rootWindow;
    XVisualInfo *xVisInfo;
    XSetWindowAttributes setWindAttrs;
    XWindowAttributes xWindAttrs;

    //GL 
    GLXContext context;
    Colormap  cmap;

    Window window;
private:

};

Answer 1

The class name system clashes with the int system(const char*) function, declared in stdlib.h, which is included by your system.h. You either need to rename the system class or move it into a namespace, because a class and a function can’t have the same name in C++.