`const char * const` vs. `const char *`: When Should You Use Each?

const char * const versus const char *

When declaring a pointer variable in C , understanding the subtle differences between these two declarations is crucial.

Example Code:

<code class="cpp">void print_string(const char * the_string)
{
    cout << the_string << endl;
}

int main () {
    print_string("What's up?");
}</code>

Declaration Differences:

• const char *: Declares a pointer to a constant character. The character itself cannot be modified, but the pointer can be reassigned to point to a different character.
• const char * const: Declares a constant pointer to a constant character. Neither the character nor the pointer itself can be modified.

Why Both Work:

In this example, both declarations work because the parameter the_string is passed a string literal: "What's up?" String literals are stored in read-only memory, meaning their contents cannot be modified.

Relevant Applications:

Using const char * const is more appropriate when you want to prevent any modifications to either the character or the pointer inside the function. This ensures data integrity and prevents unintentional changes. The verbosity of the declaration may have led the developer to use const char *, but the former is more correct.

Declaration Summary:

Declaration	Can Modify Character	Can Modify Pointer
char* the_string	Yes	Yes
const char* the_string	No	Yes
char* const the_string	Yes	No
const char* const the_string	No	No

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