Why Does C Vector's `operator[]` Allow Out-of-Bounds Access Without Errors?

Vector Accessing Out of Bounds Without Errors

When dealing with vectors in C , it's crucial to understand their behavior regarding accessing elements beyond their bounds. Unlike the at() member function which performs bounds checking and throws exceptions, accessing elements through the operator[] does not provide any such safety.

In the example provided, the vector elm.face has a size of 6, indicating it contains 6 elements. However, when the code tries to access elm.face[6], which is out of bounds, it doesn't throw an error but instead returns an unexpected number. This is because std::vector does not perform bounds checking for operator[] access.

This behavior is intentional and has its reasons. Bounds checking adds overhead and can affect performance in performance-critical applications. Therefore, C gives programmers the choice of trading safety for performance by allowing them to access elements without bounds checking.

However, this lack of bounds checking can lead to undefined results. Accessing elements beyond the vector's size can cause unpredictable behavior and potential memory issues. Therefore, it's crucial to ensure that code doesn't access vectors out of bounds and always checks the size or uses the at() function to ensure safety.

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