Aggregate initialization

Aggregate is any of following type:
- array type
- class type (struct or union) that has NO
- private, protected non-static data members
- user-declared constructors (explicitly defaulted or deleted constructors are allowed)
- virtual, private, or protected base classes
- virtual member functions
- default member initializers

Type of initialization

Type What Code
Designated initializers Each designator must name a direct non-static data member of T. Order of designator should be same as order of the data members of T 

struct A { 
    int x; 
    int y; 
    int z; 
};
A a{.y = 2, .x = 1}; // error; designator order does not match declaration order
A b{.x = 1, .z = 2}; // ok, b.y initialized to 0
Character Arrays If the size of the array is specified and it is larger than the number of characters in the string literal, the remaining characters are zero-initialized 

char a[] = "abc";                 // equivalent to char a[4] = {'a', 'b', 'c', '\0'};

//unsigned char b[3] = "abc";     // Error: initializer string too long
unsigned char b[5]{"abc"};        // equivalent to unsigned char b[5] = {'a', 'b', 'c', '\0', '\0'};
    
wchar_t c[] = {L"кошка"}; // optional braces
//equivalent to wchar_t c[6] = {L'к', L'о', L'ш', L'к', L'а', L'\0'};