error LNK2019: unresolved external symbol - c++

Question

while i want to compile my opengl code i get the following errors:
Error 1 error LNK2019: unresolved external symbol __imp__glewInit#0
Error 2 error LNK2019: unresolved external symbol __imp__glewGetErrorString#4
Error 3 error LNK2001: unresolved external symbol __imp____glewAttachShader
Error 4 error LNK2001: unresolved external symbol __imp____glewCompileShader
Error 5 error LNK2001: unresolved external symbol __imp____glewCreateProgram
Error 6 error LNK2001: unresolved external symbol __imp____glewCreateShader
Error 7 error LNK2001: unresolved external symbol __imp____glewDeleteProgram
Error 8 error LNK2001: unresolved external symbol __imp____glewDisableVertexAttribArray
Error 9 error LNK2001: unresolved external symbol __imp____glewEnableVertexAttribArray
Error 10 error LNK2001: unresolved external symbol __imp____glewGetAttribLocation
Error 11 error LNK2001: unresolved external symbol __imp____glewGetProgramiv
Error 12 error LNK2001: unresolved external symbol __imp____glewGetShaderiv
Error 13 error LNK2001: unresolved external symbol __imp____glewLinkProgram
Error 16 error LNK2001: unresolved external symbol __imp____glewVertexAttribPointer
Error 17 error LNK1120: 16 unresolved externals
my code is :
#include <Windows.h>
#include <iostream>
#include <glew.h>
#include <gl\GL.h>
#include <freeglut.h>
using namespace std;
GLuint program;
GLint attribute_coord2d;
int init_resources(void)
{
GLint compile_ok = GL_FALSE, link_ok = GL_FALSE;
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
const char *vs_source =
#ifdef GL_ES_VERSION_2_0
"#version 100\n" // OpenGL ES 2.0
#else
"#version 120\n" // OpenGL 2.1
#endif
"attribute vec2 coord2d; "
"void main(void) { "
" gl_Position = vec4(coord2d, 0.0, 1.0); "
"}";
glShaderSource(vs, 1, &vs_source, NULL);
glCompileShader(vs);
glGetShaderiv(vs, GL_COMPILE_STATUS, &compile_ok);
if (0 == compile_ok)
{
fprintf(stderr, "Error in vertex shader\n");
return 0;
}
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
const char *fs_source =
"#version 120 \n"
"void main(void) { "
" gl_FragColor[0] = 0.0; "
" gl_FragColor[1] = 0.0; "
" gl_FragColor[2] = 1.0; "
"}";
glShaderSource(fs, 1, &fs_source, NULL);
glCompileShader(fs);
glGetShaderiv(fs, GL_COMPILE_STATUS, &compile_ok);
if (!compile_ok) {
fprintf(stderr, "Error in fragment shader\n");
return 0;
}
program = glCreateProgram();
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
if (!link_ok) {
fprintf(stderr, "glLinkProgram:");
return 0;
}
const char* attribute_name = "coord2d";
attribute_coord2d = glGetAttribLocation(program, attribute_name);
if (attribute_coord2d == -1) {
fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
return 0;
}
return 1;
}
void onDisplay()
{
/* Clear the background as white */
glClearColor(1.0, 1.0, 1.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
glEnableVertexAttribArray(attribute_coord2d);
GLfloat triangle_vertices[] = {
0.0, 0.8,
-0.8, -0.8,
0.8, -0.8,
};
/* Describe our vertices array to OpenGL (it can't guess its format automatically) */
glVertexAttribPointer(
attribute_coord2d, // attribute
2, // number of elements per vertex, here (x,y)
GL_FLOAT, // the type of each element
GL_FALSE, // take our values as-is
0, // no extra data between each position
triangle_vertices // pointer to the C array
);
/* Push each element in buffer_vertices to the vertex shader */
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(attribute_coord2d);
/* Display the result */
glutSwapBuffers();
}
void free_resources()
{
glDeleteProgram(program);
}
int main(int argc, char* argv[])
{
/* Glut-related initialising functions */
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE|GLUT_DEPTH);
glutInitWindowSize(640, 480);
glutCreateWindow("My First Triangle");
/* Extension wrangler initialising */
GLenum glew_status = glewInit();
if (glew_status != GLEW_OK)
{
fprintf(stderr, "Error: %s\n", glewGetErrorString(glew_status));
return EXIT_FAILURE;
}
/* When all init functions runs without errors,
the program can initialise the resources */
if (1 == init_resources())
{
/* We can display it if everything goes OK */
glutDisplayFunc(onDisplay);
glutMainLoop();
}
/* If the program exits in the usual way,
free resources and exit with a success */
free_resources();
return EXIT_SUCCESS;
}
i tried every thing from tweaking linker option including .lib files explicitly, specifying include paths reading forums related to these errors and so on, none of them helped, can you guys help me how i fix this problem?

Answer 1

I got the glew binaries from http://glew.sourceforge.net/index.html (https://sourceforge.net/projects/glew/files/glew/1.9.0/glew-1.9.0-win32.zip/download)
and freeglut 2.8.0 MSVC Package from http://www.transmissionzero.co.uk/software/freeglut-devel/ (http://files.transmissionzero.co.uk/software/development/GLUT/freeglut-MSVC.zip)
I set the include path to glew-1.9.0\include\, freeglut\include\ and library path to freeglut\lib\, glew-1.9.0\lib\.
I corrected the header of your file as
#include <Windows.h>
#include <iostream>
#include <gl/glew.h>
#include <gl/GL.h>
#include <gl/freeglut.h>
#pragma comment(lib, "glew32.lib")
Linking successful, and it worked.
UPD
When using third-party libraries, usually:
You must set the include path to <3rdPartyDir>\include, but not to <3rdPartyDir>\include\lib_name. Declare its inclusion in the source code should be:
correct: #include <lib_name/header_name.h>
wrong: #include <header_name.h>, because within the library can be internal dependencies, for example #include <lib_name/other_header_name.h>
Set the library path to <3rdPartyDir>\lib. Then, you must specify the required libraries, one of the following methods:
For MSVC, add
#ifdef _MSC_VER
#pragma comment(lib, "lib1_name.lib")
#pragma comment(lib, "lib2_name.lib")
/// etc
#endif
Or, add the required libraries to the linker options.
Some libraries support auto-linking mechanism (for example, freeglut), that is, the header file contains a line like #pragma comment(lib, "lib1_name.lib")
Copy the required dlls from <3rdPartyDir>\bin to <MyExePath>\

Answer 2

I was having the same problem. Finally found useful instructions in this Visual Studio and OpenGL tutorial. The issue was correctly including the .dll files for the right configuration (Win32 or x64).

Answer 3

This is definitely a problem with linker settings, specifically to do with the glew library. Why your previous attempts to fix it have not worked isnt too clear to me.
Are you able to get any tutorial programs that glew provides to compile?
Edit
From your comment it looks like you are having issues including your lib file.
- Can you verify if it is where you think it is (is it installed correctly)?
- Does Visual studio know where it is supposed to be(is correct path to lib provided)?
Does Project ->Right click + properties -> Configuration Properties -> Linker -> General -> Additional Linker directories in Visual Studio have the path to the folder containing glew32.lib?

Answer 4

It seems as you used not correct glew.lib. when using config win32 to build you must use glew.lib(win32) or opposite. You can try by replace glew.lib in your project.

Answer 5

If the above answers don't work and glew seems to be linked properly, you may have simply neglected to link opengl32.lib.
In VS,
Project > Properties > Linker > Input > Additional Dependencies
and add opengl32.lib to that line if it isn't there already.