8 Statements [stmt.stmt]

Except as indicated, statements are executed in sequence ([intro.execution]).

The optional attribute-specifier-seq appertains to the respective statement.

A substatement of a statement is one of the following:

• (2.1)
  for a labeled-statement, its statement,
• (2.2)
  for a compound-statement, any statement of its statement-seq,
• (2.3)
  for a selection-statement, any of its statements or compound-statements (but not its init-statement), or
• (2.4)
  for an iteration-statement, its statement (but not an init-statement).

A statement S1 encloses a statement S2 if

• (3.1)
  S2 is a substatement of S1,
• (3.2)
  S1 is a selection-statement or iteration-statement and S2 is the init-statement of S1,
• (3.3)
  S1 is a try-block and S2 is its compound-statement or any of the compound-statements of its handlers, or
• (3.4)
  S1 encloses a statement S3 and S3 encloses S2.

A statement S1 is enclosed by a statement S2 if S2 encloses S1.

The rules for conditions apply both to selection-statements ([stmt.select]) and to the for and while statements ([stmt.iter]).

If a structured-binding-declaration appears in a condition, the condition is a structured binding declaration ([dcl.pre]).

A condition that is neither an expression nor a structured binding declaration is a declaration ([dcl.dcl]).

The declarator shall not specify a function or an array.

The decl-specifier-seq shall not define a class or enumeration.

If the auto type-specifier appears in the decl-specifier-seq, the type of the identifier being declared is deduced from the initializer as described in [dcl.spec.auto].

The decision variable of a condition that is neither an expression nor a structured binding declaration is the declared variable.

The decision variable of a condition that is a structured binding declaration is specified in [dcl.struct.bind].

The value of a condition that is not an expression in a statement other than a switch statement is the value of the decision variable contextually converted to bool ([conv]).

If that conversion is ill-formed, the program is ill-formed.

The value of a condition that is an expression is the value of the expression, contextually converted to bool for statements other than switch; if that conversion is ill-formed, the program is ill-formed.

The value of the condition will be referred to as simply “the condition” where the usage is unambiguous.

If a condition can be syntactically resolved as either an expression or a declaration, it is interpreted as the latter.

In the decl-specifier-seq of a condition, including that of any structured-binding-declaration of the condition, each decl-specifier shall be either a type-specifier or constexpr.