How do I initialize constant arrays in C class initializers, both before and after C 11?

Initialization of Constant Arrays in Class Initializers in C

In C , when declaring arrays as constant members of a class, it can be challenging to initialize them within the class constructor due to the const qualifier. This article explores how to overcome this challenge in both pre- and post-C 11 contexts.

Pre-C 11:

Prior to C 11, initializing a const array in a class initializer was not directly possible using the traditional syntax. However, there is a workaround:

<code class="cpp">class a {
    const int *b;
    int b_size;
    
    // Constructor
    a(const int *b_array, int b_sz)
        : b(b_array), b_size(b_sz) {}
};

int main() {
    int b_array[] {2, 3};
    a a(b_array, sizeof(b_array) / sizeof(int));
    // Proceed with using class 'a'
}</code>

In this approach, instead of declaring the array as a direct member, it is declared as a pointer with a corresponding size member. The constructor is then used to allocate and initialize the pointer.

Post-C 11:

With the introduction of C 11, the initialization of const arrays in class initializers became more straightforward:

<code class="cpp">struct a {
    const int b[2];
    
    // Constructor
    a() : b{2, 3} {}
};</code>

In this syntax, the curly braces {} immediately following the class member declaration allow direct initialization of the const array within the constructor.

This change in C 11 simplifies the process of initializing const arrays in class initializers and provides a more concise and elegant way to define such classes.

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