linker errors while compiling using makefile

Question

I'm working on ubuntu 14.04 LTS and am working on a shading example program. I have the following makefile:

CC=gcc
CFLAGS=-Wall -I/usr/X11R6/include
LDFLAGS=-pthread -L/usr/X11R6/lib -lm -lGL -lglut
OBJS=main.o scene.o shader.o

glsl_lighting:  $(OBJS)
    $(CC) $(LDFLAGS) $(OBJS) -o glsl_lighting

clean:
    rm -f glsl_lighting
    rm -f $(OBJS)

main.o: main.c
scene.o: scene.c
shader.o: shader.c

With the first few lines of the main file being:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "opengl.h"

This gave the following error:

gcc -pthread -L/usr/X11R6/lib -lm -lGL -lglut main.o scene.o shader.o -o glsl_lighting
main.o: In function `handleKeyPress':
main.c:(.text+0x27): undefined reference to `glutDestroyWindow'
main.o: In function `setPerspective':
main.c:(.text+0x65): undefined reference to `tanf'
main.c:(.text+0x144): undefined reference to `glMultMatrixf'
main.o: In function `main':
main.c:(.text+0x168): undefined reference to `glutInit'
main.c:(.text+0x172): undefined reference to `glutInitDisplayMode'
main.c:(.text+0x185): undefined reference to `glutInitWindowSize'
main.c:(.text+0x18f): undefined reference to `glutCreateWindow'
main.c:(.text+0x19f): undefined reference to `glutDisplayFunc'
main.c:(.text+0x1a9): undefined reference to `glutIdleFunc'
main.c:(.text+0x1b3): undefined reference to `glutKeyboardFunc'
main.c:(.text+0x1c4): undefined reference to `glClearColor'
main.c:(.text+0x1d1): undefined reference to `glClearDepth'
main.c:(.text+0x1db): undefined reference to `glDisable'
main.c:(.text+0x1e5): undefined reference to `glEnable'
main.c:(.text+0x1ef): undefined reference to `glDepthFunc'
main.c:(.text+0x1f9): undefined reference to `glEnable'
main.c:(.text+0x203): undefined reference to `glFrontFace'
main.c:(.text+0x20d): undefined reference to `glCullFace'
main.c:(.text+0x217): undefined reference to `glMatrixMode'
main.c:(.text+0x21c): undefined reference to `glLoadIdentity'
main.c:(.text+0x25c): undefined reference to `glMatrixMode'
main.c:(.text+0x266): undefined reference to `glutMainLoop'
scene.o: In function `createCylinder':
scene.c:(.text+0xf6): undefined reference to `cosf'
scene.c:(.text+0x147): undefined reference to `sinf'
scene.c:(.text+0x179): undefined reference to `cosf'
scene.c:(.text+0x1ca): undefined reference to `sinf'
scene.c:(.text+0x201): undefined reference to `cosf'
scene.c:(.text+0x252): undefined reference to `sinf'
scene.c:(.text+0x31b): undefined reference to `glGenBuffers'
scene.c:(.text+0x332): undefined reference to `glBindBuffer'
scene.c:(.text+0x358): undefined reference to `glBufferData'
scene.c:(.text+0x36e): undefined reference to `glEnableClientState'
scene.c:(.text+0x378): undefined reference to `glEnableClientState'
scene.c:(.text+0x394): undefined reference to `glVertexPointer'
scene.c:(.text+0x3ab): undefined reference to `glNormalPointer'
scene.o: In function `sceneInit':
scene.c:(.text+0x3c4): undefined reference to `glCreateProgram'
scene.c:(.text+0x40a): undefined reference to `glLinkProgram'
scene.c:(.text+0x425): undefined reference to `glGetProgramiv'
scene.c:(.text+0x44b): undefined reference to `glGetProgramiv'
scene.c:(.text+0x479): undefined reference to `glGetProgramInfoLog'
scene.c:(.text+0x4b4): undefined reference to `glDeleteProgram'
scene.c:(.text+0x4d5): undefined reference to `glGetUniformLocation'
scene.c:(.text+0x4f2): undefined reference to `glGetUniformLocation'
scene.c:(.text+0x50f): undefined reference to `glGetUniformLocation'
scene.c:(.text+0x5c5): undefined reference to `glLoadIdentity'
scene.c:(.text+0x606): undefined reference to `glTranslatef'
scene.o: In function `sceneRender':
scene.c:(.text+0x61a): undefined reference to `glClear'
scene.c:(.text+0x62c): undefined reference to `glUseProgram'
scene.c:(.text+0x648): undefined reference to `glUniform3fv'
scene.c:(.text+0x664): undefined reference to `glUniform3fv'
scene.c:(.text+0x680): undefined reference to `glUniform3fv'
scene.c:(.text+0x697): undefined reference to `glDrawArrays'
scene.c:(.text+0x6a6): undefined reference to `glUseProgram'
scene.c:(.text+0x6b7): undefined reference to `glPushMatrix'
scene.c:(.text+0x710): undefined reference to `glTranslatef'
scene.c:(.text+0x731): undefined reference to `glColor3fv'
scene.c:(.text+0x753): undefined reference to `glutSolidSphere'
scene.c:(.text+0x758): undefined reference to `glPopMatrix'
scene.c:(.text+0x76b): undefined reference to `glutSwapBuffers'
scene.o: In function `sceneCycle':
scene.c:(.text+0x8c4): undefined reference to `cosf'
scene.c:(.text+0x8f1): undefined reference to `cosf'
scene.c:(.text+0x906): undefined reference to `sinf'
scene.c:(.text+0x933): undefined reference to `sinf'
scene.c:(.text+0x957): undefined reference to `glutPostRedisplay'
shader.o: In function `shaderCompileFromFile':
shader.c:(.text+0x213): undefined reference to `glCreateShader'
shader.c:(.text+0x241): undefined reference to `glShaderSource'
shader.c:(.text+0x250): undefined reference to `glCompileShader'
shader.c:(.text+0x274): undefined reference to `glGetShaderiv'
shader.c:(.text+0x297): undefined reference to `glGetShaderiv'
shader.c:(.text+0x2c2): undefined reference to `glGetShaderInfoLog'
shader.c:(.text+0x2fe): undefined reference to `glDeleteShader'
shader.o: In function `shaderAttachFromFile':
shader.c:(.text+0x34a): undefined reference to `glAttachShader'
shader.c:(.text+0x359): undefined reference to `glDeleteShader'
collect2: error: ld returned 1 exit status

I do have glut and mesa installed and have read on some of the other questions that you should chance something in the order of the makefile but how in this instance?

Answer 1

You need to put $(LDFLAGS) (libraries) after the (object) file names, like

$(CC)  $(OBJS) -o glsl_lighting $(LDFLAGS)

As per the online gcc manual for linking options

[...] It makes a difference where in the command you write this option; the linker searches and processes libraries and object files in the order they are specified. Thus, foo.o -lz bar.o searches library z after file foo.o but before bar.o. If bar.o refers to functions in z, those functions may not be loaded.

So, the object files, using the library functions, should appear before the libraries themselves.