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I have the following simple struct, which represents an OpenGL texture:

#pragma once

#include <GL/glew.h>
#include <string>

#include "Shader.hpp"

struct Texture
{
    static constexpr GLenum UNIT[] = {GL_TEXTURE0,  GL_TEXTURE1,  GL_TEXTURE2,  GL_TEXTURE3,
                                      GL_TEXTURE4,  GL_TEXTURE5,  GL_TEXTURE6,  GL_TEXTURE7,
                                      GL_TEXTURE8,  GL_TEXTURE9,  GL_TEXTURE10, GL_TEXTURE11,
                                      GL_TEXTURE12, GL_TEXTURE13, GL_TEXTURE14, GL_TEXTURE15};
    int width, height;
    int unit;
    GLuint id;

    void use(const Shader &shader, const std::string &name) const
    {
        glActiveTexture(UNIT[unit]);
        glBindTexture(GL_TEXTURE_2D, id);
        glUniform1i(shader.getLocation(name), unit);
    }
};

The variables GL_TEXTURE0 through GL_TEXTURE15 are defined in glew.h, as per this excerpt:

#define GL_TEXTURE0 0x84C0
#define GL_TEXTURE1 0x84C1
#define GL_TEXTURE2 0x84C2
//etc...

When I try to compile my code I get the following error:

Undefined symbols for architecture x86_64:
  "Texture::UNIT", referenced from:
      Texture::use(Shader const&, std::__1::basic_string<char,     std::__1::char_traits<char>, std::__1::allocator<char> > const&) const in main.cpp.o
ld: symbol(s) not found for architecture x86_64

I obviously defined and initialized UNIT in the struct, yet it claims it doesn't exist. This error persists if I change UNIT to Texture::UNIT when it is accessed in the use method. It also persists if I change the type of UNIT to an array of integers. Why is this error being generated?

Shafik Yaghmour
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user3487347
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  • You have not defined `UNIT`. That line is not a definition. – chris Apr 15 '15 at 02:59
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    If it is [odr-used then it must have an out of class definition as well](http://stackoverflow.com/q/8016780/1708801) – Shafik Yaghmour Apr 15 '15 at 02:59
  • [This one](http://stackoverflow.com/q/23428684/1708801) is more specific to your case since you are indexing ... note that [odr violations do not require a diagnostic](http://stackoverflow.com/q/26196095/17088010). – Shafik Yaghmour Apr 15 '15 at 03:05

0 Answers0