C++ array initializer

Question

In a C++ 14 standard draft, there are two mentions (that I found) regarding array initialization:

Section 8.5.1 ([dcl.init.aggr]) paragraph 2:

"When an aggregate is initialized by an initializer list [...]"

Section 8.5.2 ([dcl.init.string]) paragraph 1:

"An array of narrow character type (3.9.1), char16_t array, char32_t array, or wchar_t array can be initialized by a narrow string literal, char16_t string literal, char32_t string literal, or wide string literal, respectively, or by an appropriately-typed string literal enclosed in braces (2.13.5). [...]"

Therefore there are at least two types of initializers that can be used for arrays: initializer lists and string literals.

Does the standard mention explicitly that these are the only two options?

No, because arrays can also be default- and value-initialized. — Kerrek SB
– Kerrek SB, Commented Aug 7, 2017 at 16:13
My wording may have been bad. I was referring to other types of (non-empty) initializers that can be used for initializing arrays. — user42768
– user42768, Commented Aug 7, 2017 at 16:23

Community · Accepted Answer · 2020-06-20 09:12:55Z

Paragraph 17 of [dcl.init] specifies all possible initializers for arrays.

17 The semantics of initializers are as follows. The destination type is the type of the object or reference being initialized and the source type is the type of the initializer expression. If the initializer is not a single (possibly parenthesized) expression, the source type is not defined.

(17.1) If the initializer is a (non-parenthesized) braced-init-list or is = braced-init-list, the object or reference is list-initialized.

(17.2) If the destination type is a reference type, see [dcl.init.ref].

(17.3) If the destination type is an array of characters, an array of char16_t, an array of char32_t, or an array of wchar_t, and the initializer is a string literal, see [dcl.init.string].

(17.4) If the initializer is (), the object is value-initialized.

(17.5) Otherwise, if the destination type is an array, the program is ill-formed.

(17.2) is not applicable to arrays, so the options are:

Default-initialization ([dcl.init]/12): int x[3];
Value-initialization ([dcl.init]/17.4): int* x = new int[3]();
List-initialization ([dcl.init]/17.1): int x[] = {1, 2, 3}; or int x[] {1, 2, 3};
Initialization with a string literal ([dcl.init]/17.3): char x[] = "text";

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