Can Arrays Be Initialized in a Constructor's Member Initializer List?

Member Array Initialization in Constructors

Consider the following C class:

class C {
public:
    C() : arr({1, 2, 3}) {}
    // C() : arr{1, 2, 3} {}
private:
    int arr[3];
};

The code attempts to initialize the arr array member in the constructor's member initializer list. However, it fails to compile.

Questions:

1. Is it possible to initialize an array in a constructor's member initializer list?
2. What does the C 03 standard state about this situation?
3. Does C 11 list initialization address this issue?

Answers:

1. Array Initialization in Constructors

Yes, it is possible to initialize an array in a constructor's member initializer list. However, it requires an intermediary structure:

struct A {
    int foo[3];
    A(int a, int b, int c) : foo{a, b, c} {}
};

class C {
public:
    C() : foo(A(1, 2, 3)) {}
private:
    A foo;
};

2. C 03 Standard

The C 03 standard does not explicitly address the initialization of arrays in member initializer lists. However, the general rules of direct initialization forbid initializing an array with braces.

3. C 11 List Initialization

C 11 introduced list initialization, which allows direct initialization of arrays using braces:

class C {
public:
    C() : arr{1, 2, 3} {}
private:
    int arr[3];
};

In this case, the syntax using braces directly after the array name is valid and initializes the array in the constructor's member initializer list.

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