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    <p>It's undefined behavior as far as I know. Run a larger program with that and it will crash somewhere along the way. Bounds checking is not a part of raw arrays (or even std::vector).</p> <p>Use std::vector with <code>std::vector::iterator</code>'s instead so you don't have to worry about it.</p> <p>Edit: </p> <p>Just for fun, run this and see how long until you crash:</p> <pre><code>int main() { int array[1]; for (int i = 0; i != 100000; i++) { array[i] = i; } return 0; //will be lucky to ever reach this } </code></pre> <p>Edit2: </p> <p>Don't run that.</p> <p>Edit3:</p> <p>OK, here is a quick lesson on arrays and their relationships with pointers:</p> <p>When you use array indexing, you are really using a pointer in disguise (called a "reference"), that is automatically dereferenced. This is why instead of *(array[1]), array[1] automatically returns the value at that value.</p> <p>When you have a pointer to an array, like this:</p> <pre><code>int array[5]; int *ptr = array; </code></pre> <p>Then the "array" in the second declaration is really decaying to a pointer to the first array. This is equivalent behavior to this:</p> <pre><code>int *ptr = &amp;array[0]; </code></pre> <p>When you try to access beyond what you allocated, you are really just using a pointer to other memory (which C++ won't complain about). Taking my example program above, that is equivalent to this:</p> <pre><code>int main() { int array[1]; int *ptr = array; for (int i = 0; i != 100000; i++, ptr++) { *ptr++ = i; } return 0; //will be lucky to ever reach this } </code></pre> <p>The compiler won't complain because in programming, you often have to communicate with other programs, especially the operating system. This is done with pointers quite a bit. </p>
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    1. POAccessing an array out of bounds gives no error, why?
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    1. COI think you forgot to increment "ptr" in your last example there. You've accidentally produced some well-defined code.
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    2. COI guess you should have ptr++ in for loop in edit3
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    3. COHaha, see why you shouldn't be using raw arrays?
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