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    <blockquote> <p>it is illegal for a vector to contain pointers to invalid memory</p> </blockquote> <p>This is what the Standard has to say about the contents of a container:</p> <p>(23.3) : The type of objects stored in these components must meet the requirements of <em>CopyConstructible</em> types (20.1.3), and the additional requirements of <em>Assignable</em> types.</p> <p>(20.1.3.1, CopyConstructible) : In the following Table 30, T is a type to be supplied by a C + + program instantiating a template, t is a value of type T, and u is a value of type const T.</p> <pre><code>expression return type requirement xxxxxxxxxx xxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxx T(t) t is equivelant to T(t) T(u) u is equivelant to T(u) t.~T() &amp;t T* denotes the address of t &amp;u const T* denotes the address of u </code></pre> <p>(23.1.4, Assignable) : 64, T is the type used to instantiate the container, t is a value of T, and u is a value of (possibly const) T.</p> <pre><code>expression return type requirement xxxxxxxxxx xxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxx t = u T&amp; t is equivilant to u </code></pre> <p>That's all that is says about the contents of an STL collection. It says nothing about pointers and it is particularly silent about the pointers pointing to valid memory.</p> <p>Therefore, <code>delete</code>ing pointers in a <code>vector</code>, while most likely a very bad architectural decision and an invitation to pain and suffering with the debugger at 3:00 AM on a Saturday night, is perfectly legal.</p> <h2>EDIT:</h2> <p>Regarding Kranar's comment that "assigning a pointer to an invalid pointer value results in undefined behavior." No, this is incorrect. This code is perfectly valid:</p> <pre><code>Foo* foo = new Foo(); delete foo; Foo* foo_2 = foo; // This is legal </code></pre> <p>What is illegal is trying to do something with that pointer (or <code>foo</code>, for that matter):</p> <pre><code>delete foo_2; // UB foo_2-&gt;do_something(); // UB Foo&amp; foo_ref = *foo_2; // UB </code></pre> <p>Simply creating a wild pointer is legal according to the Standard. Probably not a good idea, but legal nonetheless.</p> <h2>EDIT2:</h2> <p>More from the Standard regarding pointer types. </p> <p>So sayeth the Standard (3.9.2.3) :</p> <blockquote> <p>... A valid value of an object pointer type represents either the address of a byte in memory (1.7) or a null pointer (4.10)...</p> </blockquote> <p>...and regarding "a byte in memory," (1.7.1) :</p> <blockquote> <p>The fundamental storage unit in the C + + memory model is the byte. A byte is at least large enough to contain any member of the basic execution character set and is composed of a contiguous sequence of bits, the number of which is implementation-defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order bit. The memory available to a C + + program consists of one or more sequences of contiguous bytes. Every byte has a unique address.</p> </blockquote> <p>There is nothing here about that byte being part of a living <code>Foo</code>, about you having access to it, or anything of the sort. Its just a byte in memory.</p>
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    1. PODeleting a element from a vector of pointers in C++
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    1. COThank you, consider however that assigning a pointer to an invalid pointer value results in undefined behavior. Would this not then make it illegal to store an invalid pointer value in a vector, since doing so violates the assignable requirement?
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    2. CO@Kranar: I will address this in an edit of my post in a moment.
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    3. CO@Kranar: assigning a pointer to an invalid memory address does not result in undefined behavior. I think that's the problem you're having. It's perefectly legal to do, for example, `int * p = reinterpret_cast<int *>(0x34E483);`, inserting whatever value I want to create a pointer to an arbitrary address. That's *legal* C++. And that pointer now points to an invalid memory address. The only behavior that is undefined is if I later on do, for example, `*p = 12;`.
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