SDL2 + OpenGL access violation - c++

Question

This works fine:
int main(int argc, char** argv)
{
SDL_Init(SDL_INIT_VIDEO);
SDL_Window* window = SDL_CreateWindow("Game", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
SCR_WIDTH, SCR_HEIGHT, SDL_WINDOW_OPENGL);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 6);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
SDL_GLContext mainContext = SDL_GL_CreateContext(window);
gladLoadGLLoader((GLADloadproc)SDL_GL_GetProcAddress);
SDL_Event event;
int running = 1;
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
...
return 0;
}
But if I wrap the initialization into a class I get an access violation when I call glCreateShader even though I'm not getting any error messages when initializing SDL and OpenGL:
int main(int argc, char** argv)
{
WindowManager wm;
if (!wm.Construct())
return 0;
SDL_Event event;
int running = 1;
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER); //<---- access violation here
...
return 0;
}
Here is my WindowManager class with the relevant functions:
class WindowManager
{
public:
WindowManager() = default;
bool Construct()
{
if (SDL_Init(SDL_INIT_VIDEO) < 0);
return false;
mWindow = SDL_CreateWindow("Game", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width,
height, SDL_WINDOW_OPENGL);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 6);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
mContext = SDL_GL_CreateContext(mWindow);
if (!mWindow)
{
spdlog::error("WindowManager could not be created!");
return false;
}
if (!gladLoadGLLoader((GLADloadproc)SDL_GL_GetProcAddress))
{
spdlog::error("Failed to initialize GLAD!");
return false;
}
return true;
}
SDL_Window* mWindow;
SDL_GLContext mContext;
};
If anyone could some shine some light on what the issue could be I would greatly appreciate it!

Answer 1

Since I was compiling WindowManager into a dll and using it in a separate project, I essentially made two programs.
Program A had an initialized OpenGL context but Program B that was using WindowManager did not.
So I had to write a function to expose the glProcAddress to Program B in order to make raw OpenGL calls such as glCreateShader().