VisualC++ compiler error C3646: unknown override specifier

Question

I'm trying to code a simple DirectX11 engine but I keep getting this strange error and I can't find the problem: I define a Terrain class and a Mesh class and #include the Mesh class in the Terrain class:

the Terrain class definition:

// Terrain.h
#pragma once

#include "Noise.h"
#include "Mesh.h"

class Terrain
{
public:
    Terrain(float width, float depth, int numVerticesW, int numVerticesD);
    ~Terrain();
    float GetHeight(float x, float z);
    void Draw();
private:
    Mesh mMesh;                     // I get the error on this line 
    Noise mNoiseGenerator;
    std::vector<float> mHeights;
    void CreateTerrain(float width, float depth, int numVerticesW, int numVerticesD);
    float ComputeHeight(float x, float z, float startFrequency, float startAmplitude, float persistence, int octaves);
};

and the Mesh class definition:

// Mesh.h
#pragma once

#include <d3d11.h>
#include <vector>
#include "Game.h"

class Mesh
{
public:
    Mesh();
    ~Mesh();
    template <typename T, unsigned int N> 
    void LoadVertexBuffer(T data[][N], unsigned int size, bool dynamic = false);
    void LoadIndexBuffer(std::vector<unsigned int> indices);
    void SetVertexCount(unsigned int vertexCount);
    void Bind();
    void Draw();
private:  
    std::vector<ID3D11Buffer*> mVertexBuffers;
    std::vector<unsigned int> mStrides;
    ID3D11Buffer *mIndexBuffer;
    unsigned int mVertexCount;
};


template <typename T, unsigned int N>
void Mesh::LoadVertexBuffer(T data[][N], unsigned int size, bool dynamic)
{
    D3D11_BUFFER_DESC bufferDesc = {};
    bufferDesc.Usage = dynamic ? D3D11_USAGE_DYNAMIC : D3D11_USAGE_IMMUTABLE;
    bufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
    bufferDesc.ByteWidth = sizeof(T[N]) * size;
    bufferDesc.CPUAccessFlags = dynamic ? D3D11_CPU_ACCESS_WRITE : 0;
    bufferDesc.MiscFlags = 0;
    bufferDesc.StructureByteStride = 0;

    D3D11_SUBRESOURCE_DATA bufferData = {}; 
    bufferData.pSysMem = data;

    ID3D11Buffer *buffer;
    Game::GetInstance()->GetDevice()->CreateBuffer(&bufferDesc, &bufferData, &buffer);
    mVertexBuffers.push_back(buffer);
    mStrides.push_back(sizeof(T[N]));
}

When I compile the code I get:

Severity    Code    Description Project File    Line    Suppression State
Error   C3646   'mMesh': unknown override specifier DirectX11 engine 0.3    c:\users\luca\desktop\programming\code\c++\source\visual studio\directx11 engine 0.3\terrain.h  14  
Severity    Code    Description Project File    Line    Suppression State
Error   C4430   missing type specifier - int assumed. Note: C++ does not support default-int    DirectX11 engine 0.3    c:\users\luca\desktop\programming\code\c++\source\visual studio\directx11 engine 0.3\terrain.h  14  

I searched the web but most results show missing semicolons or circular inclusion issues but I can't find any.

EDIT I found the issue but I can't explain why my solution works: following the inclusion tree: Terrain.h --> Mesh.h --> Game.h --> Renderer.h --> Terrain.h

eliminating #include "Terrain.h" (since I just declare Terrain * pointers inside the class) and adding it to Terrain.cpp seems to solve the issue. So it must be a matter of circular inclusion, but shouldn't I be guarded against that by using header/include guards?

Answer 1

Your problem is that #pragma once only prevents against double inclusion. I.e. it makes the following safe (simplified to make it obvious) :

// Terrain.cpp
#include "Terrain.h"
#include "Terrain.h" 

It does not solve circular inclusion, which is far harder to solve automatically. With double inclusion, it's clear which one is first. But a circle has no begin.