Linking glfw g++

Question

I have been trying to code with OpenGL without using a IDE, but the manual linking is really confusing me. I have a folder with the libglfw3.a, glfw3.h and a .cpp file with this example code.

#include "glfw3.h"

int main(void)
{
    GLFWwindow* window;

    /* Initialize the library */
    if (!glfwInit())
        return -1;

    /* Create a windowed mode window and its OpenGL context */
    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }

    /* Make the window's context current */
    glfwMakeContextCurrent(window);

    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    {
        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT);

        /* Swap front and back buffers */
        glfwSwapBuffers(window);

        /* Poll for and process events */
        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}

I compile it like this.

g++ source.cpp -lglfw3 -o program

Yet I get these errors.

C:\Users\murra\Coding\Manual>g++ source.cpp -lglfw3 -o proc
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0x17): undefined reference to `glfwInit'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0x56): undefined reference to `glfwCreateWindow'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0x64): undefined reference to `glfwTerminate'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0x76): undefined reference to `glfwMakeContextCurrent'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0x81): undefined reference to `glfwWindowShouldClose'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0x96): undefined reference to `_imp__glClear@4'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0xa6): undefined reference to `glfwSwapBuffers'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0xab): undefined reference to `glfwPollEvents'
C:\Users\murra\AppData\Local\Temp\ccO7xs1Q.o:source.cpp:(.text+0xb2): undefined reference to `glfwTerminate'
collect2.exe: error: ld returned 1 exit status

I'm quite new to this stuff so help would be appreciated.

Answer 1

When you link a third party lib, you need to "tell" the compiler the location of the headers as well as the location of the libraries.

Typically, one would use -I<header_dir> and -L<lib_dir> in addition to -l<lib_name>

You may also reduce this to 2 steps by using -I<header_dir> and -L<full_lib_path>

If linking causes errors, IMO there are 3 major reasons.

1. Incorrect path
2. Mixing shared lib and static lib flags (example - -MT and -MD on VS)
3. Additional library dependencies that you have not included.

In your case, the missing symbols seem to be from additional libs. Try -lglfw3 -lglew32 -lopengl32 -lgdi32 as additional options. Obviously these need to be on your computer.