


Why does a modified constant variable retain its original value at compile time, even though a non-const pointer allows for modification of its actual value?
Nov 01, 2024 pm 07:33 PMModifying a Constant through a Non-Const Pointer
In the given code, a constant variable e is initialized to 2. A non-const pointer w is then cast to point to the address of e, implicitly removing the const-ness of the variable. By dereferencing w and assigning a new value to it, the value at the address of e is modified from 2 to 5.
However, when the values of *w and e are printed, they appear different:
<code class="cpp">cout << *w << endl; // Outputs 5 cout << e << endl; // Outputs 2</code>
This behavior can be explained by considering the different ways in which *w and e are evaluated:
- *w is being evaluated at runtime: The compiler recognizes that *w is a non-const pointer and dynamically retrieves the value at the address pointed to by w. Since the value at that address has been modified to 5, *w correctly outputs 5.
- e is being treated as a compile-time constant: The compiler recognizes that e is a constant variable and evaluates its value at compile time. Since the value of e has not been modified at compile time, the compiler continues to treat it as 2.
Therefore, the difference in values arises from the distinct evaluation times of *w and e. Despite the modification to the value at the address of e, the constant variable itself remains unmodified at compile time. However, the non-const pointer w allows for modification of the value at the address it points to, resulting in the output of 5 for *w.
The above is the detailed content of Why does a modified constant variable retain its original value at compile time, even though a non-const pointer allows for modification of its actual value?. For more information, please follow other related articles on the PHP Chinese website!

Hot Article

Hot tools Tags

Hot Article

Hot Article Tags

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

C language function format letter case conversion steps

What are the types of values returned by c language functions? What determines the return value?

What are the definitions and calling rules of c language functions and what are the

How does the C Standard Template Library (STL) work?

Where is the return value of the c language function stored in memory?

How do I use algorithms from the STL (sort, find, transform, etc.) efficiently?
