Enumeration constant declaration vs. definition - C standard

Question

The C11 standard specifies in section 6.7/5:

C11 6.7/5

A definition of an identifier is a declaration for that identifier that:

(...)

— for an enumeration constant, is the (only) declaration of the identifier;

(...)

Does the wording of the above paragraph state that

A definition of an enumeration constant is a declaration that is the (only) declaration
A definition of an enumeration constant is the (only) declaration?

It means that you cannot declare an enumeration constant without also defining it. It also means you can't forward declare enumeration constants. However, scoping still applies so you could have: `enum { NAME1, NAME2 }; void function(void) { enum { NAME1 = 37, NAME2 = -57 }; … }`. — Jonathan Leffler, Aug 29 '18 at 17:51

score 1 · Answer 1 · edited Aug 29 '18 at 18:58

1

It means that declaring an enumeration constant also defines it.

As a result, an enum constant cannot appear more than once in a scope within a translation unit. For example, the code below is invalid as it redeclares an enum constant:

enum a {
    AAA,
    BBB
};

enum b {
    BBB,   // error, redeclaration
    CCC
};

edited Aug 29 '18 at 18:58

Jonathan Leffler

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answered Aug 29 '18 at 17:59

dbush

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So it's 2.? Because 1. would not make any sense. – Sinushyperbolikus Aug 29 '18 at 18:10
@Sinushyperbolikus Correct. Since there can be only one declaration (which is also the definition) it doesn't make sense to talk about multiple declarations. – dbush Aug 29 '18 at 18:11

Enumeration constant declaration vs. definition - C standard

1 Answers1