D3DReflect does not detect constant buffers

Question

So i am trying to get the number of constant buffers from my compiled shaders through reflection. Sadly it is not working as expected and i don't know why. Here is how i load the shader code inside a ID3DBlob:

ID3DBlob* vertexBlob;
HRESULT result = D3DReadFileToBlob(vertexShader.c_str(), &vertexBlob);

And this is how i get the reflection:

ComPtr<ID3D11ShaderReflection> reflection;
HRESULT hr = D3DReflect(shader.code->GetBufferPointer(), shader.code->GetBufferSize(), IID_ID3D11ShaderReflection, reinterpret_cast<void**>(reflection.GetAddressOf()));

if (FAILED(hr)) {
    // SOMETHING WENT WRONG;
    return (nullptr);
}

D3D11_SHADER_DESC shaderDesc;
reflection->GetDesc(&shaderDesc);

If i check the shaderDesc in Debug the ConstantBuffers variable is 0. I already made sure that changes made to the Shader are getting recognized. I added another input variable and the number of input parameters inside the description increased. Finally here is how i define the constant buffer, but i don't think that this is the problem:

cbuffer perObject 
{
    matrix worldViewProj;
};

struct vertexInput
{
    float3 position : POSITION;
    float3 color : COLOR;
};

float4 main(vertexInput input) : SV_POSITION
{
    return float4(input.position, 1.0f);
}

Has anyone any ideas what might be wrong?

Answer 1

As you don't use your constant buffer in the shader, it's probably optimised away during compilation.

Temporarily, change your shader so you make sure it gets used and then see what you get on reflection:

float4 main(vertexInput input) : SV_POSITION
{
    return mul(float4(input.position, 1.0f), worldViewProj);
}