Why am I allowed to call this->deviceContext->map() from a const member function?

Question

I don't understand why this is allowed:

void Renderer::UpdateTextureFromArray(unsigned int* colors, unsigned int size, TextureData* textureData) const
{
    D3D11_MAPPED_SUBRESOURCE ms;
    this->deviceContext->Map(textureData->texture, 0, D3D11_MAP_WRITE_DISCARD, NULL, &ms);

    memcpy(ms.pData, colors, sizeof(unsigned int) * size * size);
    this->deviceContext->Unmap(textureData->texture, 0);
}

I made the UpdateTextureFromArray function const, yet I'm still allowed to call a non-const function on its members?

In this case, is it bad style for me to label the function as const?

EDIT: To clarify, is it "lying" to society if I have a function like this const? In a perfect world, this code wouldn't compile, right?

Answer 1

Presumably deviceContext is a pointer data member, so a const method cannot modify the pointer. But is is allowed to modify the object the pointer points to:

struct Bar {
  void bar() {} // non const method
};

struct Foo {
  Foo() : p(0) {}
  void foo() const { p->bar();} // const method calling non-const method of Bar
  Bar* p;
};

int main()
{
  const Foo f;
  f.foo();  // OK, Foo::p is not modified
}