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POWhy do I get SIGSEGV error when use class function from pointer?
 

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  1. POWhy do I get SIGSEGV error when use class function from pointer?
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    <p>I'm new in C++ and runned into first trouble. I have a GameObject class in which I have to somehow store many components. Each component is a different class, so I can't just normally use vector. I decided to store a component's type and pointer to that object. The problem is, that when I get, return that component, and use a class function which uses it's member variables, I get SIGSEGV error(yeah, sounds confusing). However, if I normally use that class and that function, I don't get a SIGSEGV error.</p> <p><strong>GameObject.h:</strong></p> <pre><code>enum ComponentType { MeshComponent // currently only one type }; struct Component { ComponentType type; void *pointer; }; class GameObject { private: std::vector&lt;Component&gt; components; public: void addComponent(ComponentType type); template&lt;typename T&gt; T* getComponent() { for(std::vector&lt;Component&gt;::size_type i = 0; i != components.size(); i++) { // will need to somehow check T type later if(components[i].type == MeshComponent) { return (Mesh*)&amp;components[i].pointer; } } Debug::Loge(GAMEOBJECT_TAG, "No %s component in %s gameobject!", componentTypeToString(MeshComponent).c_str(), name.c_str()); return 0; } } </code></pre> <p><strong>GameObject.cpp:</strong></p> <pre><code>void GameObject::addComponent(ComponentType type) { Component component; component.type = type; if(type == MeshComponent) { Mesh *mesh = new Mesh(); component.pointer = &amp;mesh; } components.push_back(component); } </code></pre> <p><strong>Mesh.h</strong></p> <pre><code>class Mesh { public: Mesh *setMeshData(std::vector&lt;GLfloat&gt; data); }; </code></pre> <p><strong>Mesh.cpp</strong></p> <pre><code>Mesh *Mesh::setMeshData(vector&lt;GLfloat&gt; data) { meshData = data; return this; } </code></pre> <p>And finally this is how I use it:</p> <pre><code>GameObject object; void somefunction() { object.addComponent(MeshComponent); object.getComponent&lt;Mesh&gt;()-&gt;setMeshData(triangle_data); // SIGSEGV HERE!! // if I use this one instead above - no sigsegv, everything is fine. Mesh mesh; mesh.setMeshData(triangle_data); } </code></pre>
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    1. CO`return (Mesh*)&components[i].pointer;` Quick skim - looks like you are getting the pointer you want (`.pointer`) then taking the address of *the pointer* and returning that.
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    2. COYou should at the very least check that ``object.getComponent<Mesh>()`` does not return ``0``.
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    3. COA std::vector<std::unique<Component>> might make life easier if you've got C++11
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