Why redeclaration of a static member is denied

Question

I thought that we can redeclare a name any times in any context. But

class A 
{
    static int a;
    static int a;
};

returns a compile-time error:

test.cpp:4:13: error: redeclaration of ‘int A::a’
test.cpp:3:13: note: previous declaration ‘int A::a’

What names can be redeclare actually?

Wasn´t this answered some minutes ago in you previous question? — deviantfan, May 13 '14 at 07:32
how do you make the difference between the first and the second `a` ? — Raxvan, May 13 '14 at 07:33
@Raxvan I'm interested in where this redeclaration denied in the standard. Can you answer me? — St.Antario, May 13 '14 at 07:34
@St.Antario: Not really, the are only the other way around and should get the same answer. See Mike Seymours comment: http://stackoverflow.com/questions/23624844/one-definition-rule-in-c#comment36274096_23624863 — deviantfan, May 13 '14 at 07:38

score 2 · Answer 1 · answered May 13 '14 at 07:40

According to the C++ Standard (9.2 Class members, paragraph #1)

A member shall not be declared twice in the member-specification, except that a nested class or member class template can be declared and then later defined, and except that an enumeration can be introduced with an opaque-enum-declaration and later redeclared with an enum-specifier.

score 1 · Accepted Answer · answered May 13 '14 at 07:41

C++11 9.2/1 [class.mem]

A member shall not be declared twice in the member-specification, except that a nested class or member class template can be declared and then later defined, and except that an enumeration can be introduced with an opaque-enum-declaration and later redeclared with an enum-specifier.

score 0 · Answer 3 · answered May 13 '14 at 07:45

0

Beside the other answers, your code is not only a redeclaration but also a redefinition, which clearly violates the one-definition-rule.

answered May 13 '14 at 07:45

bjhend

1,538
11
25

There is no any redefinition. Actually, `declaration is a definition unless it declares a function without specifying the function’s body (8.4), it contains the extern specifier (7.1.1) or a linkage-specification 25 (7.5) and neither an initializer nor a function-body, it declares a static data member in a class definition (9.2, 9.4)` – St.Antario May 13 '14 at 07:50
For more details please see 3.1.2 section – St.Antario May 13 '14 at 07:50
You're right. I've read too quickly and missed that you define a class not a function. – bjhend May 13 '14 at 07:59

Why redeclaration of a static member is denied

3 Answers3