This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115d. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-10-26

2475. Object declarations of type cv void

[Accepted as a DR at the February, 2023 meeting.]

(From editorial issue 3953.)

Although an object cannot be defined with a type of cv void, there is nothing preventing a non-defining declaration of an object with that type. Should it be disallowed?

Notes from the December, 2020 teleconference:

Such declarations are permitted in C, so this question was referred to the C liaison for investigation.

CWG 2022-11-11

CWG resolved to making such declarations ill-formed.

Proposed resolution (approved by CWG 2022-12-02; amended 2023-02-06):

Change in 9.1 [dcl.pre] paragraph 7 as follows:

If the decl-specifier-seq contains the typedef specifier, the declaration is called a typedef declaration and each declarator-id is declared to be a typedef-name, synonymous with its associated type (9.2.4 [dcl.typedef]). [ Note 4: Such a declarator-id is an identifier (11.4.8.3 [class.conv.fct]). —end note] If the decl-specifier-seq contains no typedef specifier, Otherwise, if the type associated with a declarator-id is a function type (9.3.4.6 [dcl.fct]), the declaration is called a function declaration if the type associated with a declarator-id is a function type (9.3.4.6 [dcl.fct]) and . Otherwise, if the type associated with a declarator-id is an object or reference type, the declaration is an object declaration otherwise. Otherwise, the program is ill-formed.

[ Example:

int f(), x;            // OK, function declaration for f and object declaration for x
extern void g(),       // OK, function declaration for g
  y;                   // error: void is not an object type

-- end example ]