How Can a Const Variable and a Non-Const Pointer Show Different Values at the Same Memory Address?

Two Values at the Same Address: A Const Variable Mystery

This code demonstrates an intriguing behavior involving const variables and memory addresses. The provided code contains a const integer N assigned to 22. It then uses a const_cast to convert the address of N to a non-const pointer pN and assigns the value 33 to it.

When examining the output, we observe two different values at the same memory address. The variable N remains unchanged at 22, but *pN shows the modified value of 33.

However, it's crucial to understand that there is only one value stored at that memory address. The compiler is taking advantage of the optimization allowed for const variables. This optimization treats any reference to N as its compile-time value, which is 22. Therefore, even though pN is pointing to the same memory address, it is effectively pointing to the optimized value, resulting in the output shown.

It's important to note that the compiler's optimizations can extend beyond const variables. As a general rule, it can make modifications to improve code efficiency, including removing unnecessary memory accesses, rearranging instructions, and even removing portions of code if they are deemed irrelevant. While these optimizations generally enhance performance, they can sometimes lead to unexpected results like the example observed here.

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