[dcl.attr.grammar] (original) (raw)

9 Declarations [dcl.dcl]

9.12 Attributes [dcl.attr]

9.12.1 Attribute syntax and semantics [dcl.attr.grammar]

If an attribute-specifiercontains an attribute-using-prefix, the attribute-list following that attribute-using-prefixshall not contain an attribute-scoped-tokenand every attribute-token in that attribute-listis treated as if its identifier were prefixed with N​::​, where N is the attribute-namespacespecified in the attribute-using-prefix.

[ Note

:

This rule imposes no constraints on how an attribute-using-prefixaffects the tokens in an attribute-argument-clause.

— end note

]

[ Example

:

[[using CC: opt(1), debug]]
void f() {} [[using CC: opt(1)]] [[CC::debug]]
void g() {} [[using CC: CC::opt(1)]]
void h() {}

— end example

]

[ Note

:

For each individual attribute, the form of thebalanced-token-seq will be specified.

— end note

]

In an attribute-list, an ellipsis may appear only if thatattribute's specification permits it.

An attribute-specifier that contains no attributes has no effect.

The order in which the attribute-tokens appear in anattribute-list is not significant.

If akeywordor an alternative token that satisfies the syntactic requirements of an identifier is contained in an attribute-token, it is considered an identifier.

Noname lookup is performed on any of the identifiers contained in anattribute-token.

The attribute-token determines additional requirements on the attribute-argument-clause (if any).

Each attribute-specifier-seq is said to appertain to some entity or statement, identified by the syntactic context where it appears ([stmt.stmt], [dcl.dcl],[dcl.decl]).

If an attribute-specifier-seq that appertains to some entity or statement contains an attribute or alignment-specifier that is not allowed to apply to that entity or statement, the program is ill-formed.

If an attribute-specifier-seqappertains to a friend declaration ([class.friend]), that declaration shall be a definition.

For an attribute-token(including an attribute-scoped-token) not specified in this document, the behavior is implementation-defined.

Any attribute-token that is not recognized by the implementation is ignored.

An attribute-token is reserved for future standardization if

• it is not an attribute-scoped-token and is not specified in this document, or
• it is an attribute-scoped-token and its attribute-namespace isstd followed by zero or more digits.

[ Note

:

Each implementation should choose a distinctive name for theattribute-namespace in an attribute-scoped-token.

— end note

]

Two consecutive left square bracket tokens shall appear only when introducing an attribute-specifier or within the balanced-token-seq of an attribute-argument-clause.

[ Note

:

If two consecutive left square brackets appear where an attribute-specifier is not allowed, the program is ill-formed even if the brackets match an alternative grammar production.

— end note

]

[ Example

:

int p[10]; void f() { int x = 42, y[5]; int(p[[x] { return x; }()]);

y[[] { return 2; }()] = 2;
int i [[vendor::attr([[]])]]; }

— end example

]