[SOLVED] gl.h not linking

Al99 · 01-25-2024, 04:01 AM

Hi I am doing the tutorial at https://lazyfoo.net/tutorials/OpenGL...ngl/index2.php

I have

main.cpp
https://drive.google.com/file/d/1tHB...usp=drive_link

LUtil.cpp
https://drive.google.com/file/d/10GN...usp=drive_link

LUtil.h
https://drive.google.com/file/d/1dtW...usp=drive_link

LOpenGL.h
https://drive.google.com/file/d/1Rkt...usp=drive_link

I am compiling with
g++ main.cpp LUtil.cpp -lGLU -lGL -lfreeglut

and I get

LUtil.cpp: In function ‘bool initGL()’:
LUtil.cpp:4:15: error: ‘GL_PROJECTION’ was not declared in this scope
4 | glMatrixMode( GL_PROJECTION );
| ^~~~~~~~~~~~~
LUtil.cpp:4:1: error: ‘glMatrixMode’ was not declared in this scope
4 | glMatrixMode( GL_PROJECTION );
| ^~~~~~~~~~~~
LUtil.cpp:5:1: error: ‘glLoadIdentity’ was not declared in this scope
5 | glLoadIdentity();
| ^~~~~~~~~~~~~~
LUtil.cpp:8:15: error: ‘GL_MODELVIEW’ was not declared in this scope
8 | glMatrixMode( GL_MODELVIEW );
| ^~~~~~~~~~~~
LUtil.cpp:10:1: warning: no return statement in function returning non-void [-Wreturn-type]
10 | }
| ^
LUtil.cpp: At global scope:
LUtil.cpp:13:13: error: expected constructor, destructor, or type conversion before ‘(’ token
13 | glClearColor( 0.f, 0.f, 0.f, 1.f );
| ^
LUtil.cpp:16:1: error: ‘GLenum’ does not name a type; did you mean ‘enum’?
16 | GLenum error = glGetError();
| ^~~~~~
| enum
LUtil.cpp:17:1: error: expected unqualified-id before ‘if’
17 | if( error != GL_NO_ERROR )
| ^~
LUtil.cpp:22:1: error: expected unqualified-id before ‘return’
22 | return true;
| ^~~~~~
LUtil.cpp:23:1: error: expected declaration before ‘}’ token
23 | }
| ^
LUtil.cpp: In function ‘void render()’:
LUtil.cpp:31:14: error: ‘GL_COLOR_BUFFER_BIT’ was not declared in this scope
31 | glClear( GL_COLOR_BUFFER_BIT );
| ^~~~~~~~~~~~~~~~~~~
LUtil.cpp:31:5: error: ‘glClear’ was not declared in this scope
31 | glClear( GL_COLOR_BUFFER_BIT );
| ^~~~~~~
LUtil.cpp: At global scope:
LUtil.cpp:35:8: error: expected constructor, destructor, or type conversion before ‘(’ token
35 | glBegin( GL_QUADS );
| ^
LUtil.cpp:36:15: error: expected constructor, destructor, or type conversion before ‘(’ token
36 | glVertex2f( -0.5f, -0.5f );
| ^
LUtil.cpp:37:15: error: expected constructor, destructor, or type conversion before ‘(’ token
37 | glVertex2f( 0.5f, -0.5f );
| ^
LUtil.cpp:38:15: error: expected constructor, destructor, or type conversion before ‘(’ token
38 | glVertex2f( 0.5f, 0.5f );
| ^
LUtil.cpp:39:15: error: expected constructor, destructor, or type conversion before ‘(’ token
39 | glVertex2f( -0.5f, 0.5f );
| ^
LUtil.cpp:40:8: error: expected constructor, destructor, or type conversion before ‘;’ token
40 | glEnd();
| ^
LUtil.cpp:43:18: error: expected constructor, destructor, or type conversion before ‘;’ token
43 | glutSwapBuffers();
| ^
LUtil.cpp: In function ‘void runMainLoop(int)’:
LUtil.cpp:52:27: error: ‘SCREEN_FPS’ was not declared in this scope
52 | glutTimerFunc( 1000 / SCREEN_FPS, runMainLoop, val );
| ^~~~~~~~~~
LUtil.cpp:52:5: error: ‘glutTimerFunc’ was not declared in this scope
52 | glutTimerFunc( 1000 / SCREEN_FPS, runMainLoop, val );

As far as I know these functions and types are defined in gl.h

why am I getting these errors?

thanks.

Keith Hedger · 01-25-2024, 06:22 AM

if you are using one of the distros that split the development files into seperate packages ( debian etc ) you need to install them as well.
You also need to tell the compiler wher to find the header files, try:

Code:

keithhedger@Marvin [ / ]$ pkg-config --cflags gl --libs
-I/usr/include/libdrm -lGL

teckk · 01-25-2024, 12:57 PM

Putting that together into one block of code.

HelOpGl.cpp

Code:

#include <GL/freeglut.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <stdio.h>

//Screen Constants
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_FPS = 60;

bool initGL();
void update();
void render();

bool initGL() {
    //Initialize Projection Matrix
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();

    //Initialize Modelview Matrix
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();
    
    //Initialize clear color
    glClearColor( 0.f, 0.f, 0.f, 1.f );

    //Check for error
    GLenum error = glGetError();
    if( error != GL_NO_ERROR ) {
        printf( "Error initializing OpenGL! %s\n", gluErrorString( error ) );
        return false;
    }

    return true;
}

void update(){
}

void render(){
    //Clear color buffer
    glClear( GL_COLOR_BUFFER_BIT );
    //Render quad
    glBegin( GL_QUADS );
        glVertex2f( -0.5f, -0.5f );
        glVertex2f(  0.5f, -0.5f );
        glVertex2f(  0.5f,  0.5f );
        glVertex2f( -0.5f,  0.5f );
    glEnd();
    //Update screen
    glutSwapBuffers();
}

void runMainLoop( int val );

int main( int argc, char* args[] )
{
    //Initialize FreeGLUT
    glutInit( &argc, args );
    
    //Create OpenGL 2.1 context
    glutInitContextVersion( 2, 1 );
    
    //Create Double Buffered Window
    glutInitDisplayMode( GLUT_DOUBLE );
    glutInitWindowSize( SCREEN_WIDTH, SCREEN_HEIGHT );
    glutCreateWindow( "OpenGL" );
    
    //Do post window/context creation initialization
    if( !initGL() )
    {
        printf( "Unable to initialize graphics library!\n" );
        return 1;
    }
    
    //Set rendering function
    glutDisplayFunc( render );
    
    //Set main loop
    glutTimerFunc( 1000 / SCREEN_FPS, runMainLoop, 0 );
    
    //Start GLUT main loop
    glutMainLoop();

    return 0;
}

void runMainLoop( int val ){
    //Frame logic
    update();
    render();

    //Run frame one more time
    glutTimerFunc( 1000 / SCREEN_FPS, runMainLoop, val );
}

I was able to compile that with

Code:

g++ HelOpGl.cpp -lm -lGL -lGLU -lglut -Wall -Werror -o HelOpGl

https://0x0.st/HGv4.png

Al99 · 01-29-2024, 06:29 AM

teckk: thanks for compiling this.
Why doesn't the compiler see gl h in the desperate files?

I want to stay as close to the tutorial as possible. Thanks.

pan64 · 01-29-2024, 06:39 AM

Probably you need to specify the location
g++ -I <include dir> .....

Al99 · 01-29-2024, 06:50 AM

Do I do it all in one go when I compile?

teckk · 01-29-2024, 07:40 AM

Starting with LUtil.cpp LUtil.h main.cpp LOpenGL.h in a directory.

To compile that with:

Code:

g++ main.cpp LUtil.cpp -lm -lGL -lGLU -lglut -Wall -o Test

I had to add to the top of LUtil.cpp

Code:

#include "LOpenGL.h"
#include "LUtil.h"

The four code files listed on
https://lazyfoo.net/tutorials/OpenGL...ngl/index2.php

Al99 · 02-01-2024, 04:59 AM

Putting those includes in solved the problem. Thanks.