A value type will never act polymorphically, its type is set in stone at compile time. Only through using a pointer or reference can a given piece of code be passed different types at runtime.

You can expose the value as a reference too, which is slightly safer:

// Renderer.h

Renderer &getGlobalRenderer();

// Main.cpp

namespace {
    Renderer *globalRenderer = 0;
}

Renderer &getGlobalRenderer() {
    assert(globalRenderer);
    return *globalRenderer;
}

int main() {
    Renderer renderer;
    globalRenderer = &renderer;

    // Rest of program

    globalRenderer = 0;
}

This mechanism allows you to hide the dangerous raw pointer in main(), but yet still expose the global value. Note that this approach avoids dynamically allocating the renderer - but doesn't prevent you from doing so either. This also simplifies cleanup - the renderer will naturally be destroyed at the end of main(), or if you return early, or if an exception is thrown.

A value type will never act polymorphically, its type is set in stone at compile time. Only through using a pointer or reference can a given piece of code be passed different types at runtime.

You can expose the value as a reference too, which is slightly safer:

// Renderer.h

Renderer &getGlobalRenderer();

// Main.cpp

namespace {
    Renderer *globalRenderer = 0;
}

Renderer &getGlobalRenderer() {
    assert(globalRenderer);
    return *globalRenderer;
}

int main() {
    Renderer renderer;
    globalRenderer = &renderer;

    // Rest of program

    globalRenderer = 0;
}

This mechanism allows you to hide the dangerous raw pointer in main(), but yet still expose the global value. Note that this approach avoids dynamically allocating the renderer - but doesn't prevent you from doing so either. This also simplifies cleanup - the renderer will naturally be destroyed at the end of main(), or if you return early, or if an exception is thrown.