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POHow to create an array while potentially using placement new
 

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    <p>I have been working on creating a custom allocator as a fun exercise/practice and I ran into two potentials issues with creating arrays. For a typical call for allocation, I will use <code>malloc</code> and <code>placement new</code>. However, when I go to create an array I am confused on how it should be done. For once, I have noticed at some places that it seems <code>placement new</code> may not be safe for arrays such as <a href="https://stackoverflow.com/questions/4011577/placement-new-array-alignment">here</a>. I am also running into an error of my own while attempting to use <code>placement new</code> for an array. I will get the error of</p> <blockquote> <p>`error C2679: binary '=' : no operator found which takes a right-hand operand of type 'SomeClass *' (or there is no acceptable conversion)</p> </blockquote> <p>I understand the error (I believe) but I would prefer to have the error be solved via my array construction method. I have two questions</p> <p>1) How can an allocator create an array without using <code>new[]</code>? Is it with <code>placement new</code>? If so, what about the potential dangers mentioned from the link I posted above?</p> <p>2) If I am suppose to use <code>placement new</code> and call it on each one of the elements in the array, why am I getting the error mentioned above?</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;new&gt; class SomeClass{ public: SomeClass() { printf("Constructed\n"); } ~SomeClass() { printf("Destructed\n"); } }; void* SomeAllocationFunction(size_t size) { return malloc(size); } template&lt;typename Type&gt; Type* SomeArrayAllocationFunction(size_t count){ Type* mem = (Type*)SomeAllocationFunction(sizeof(Type) * count); for(unsigned int i = 0; i &lt; count; ++i) { mem[i] = new(mem + i) Type(); } return mem; } int main(void){ SomeClass* t = SomeArrayAllocationFunction&lt;SomeClass&gt;(2); } </code></pre>
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