Issue 0013.05: When is the sizeof an enumeration type known?

This issue has been automatically converted from the original issue lists and some formatting may not have been preserved.

Authors: Sam Kendall, WG14
Date: 1992-12-10
Reference document: X3J11/90-047
Submitted against: C90
Status: Fixed
Fixed in: C90 TC1
Cross-references: 0118, 0165
Converted from: dr.htm, dr_013.html

Enumeration tag anomaly

Consider the following (bizarre) example:

enum strange1 {
         a = sizeof (enum strange1)      /* line [2] */
 };
 enum strange2 {
         b = sizeof (enum strange2 *)    /* line [5] */
 };

The respective tags are visible on lines [2] and [5] (according to subclause 6.1.2.1, page 20, lines 39-40, but there is no rule in subclause 6.5.2.3, Semantics (page 62) that governs their meaning on lines [2] and [5]. Footnote 62 on page 62 seems to be written without taking this case into account.

The first declaration must be illegal. The second declaration should be illegal for simplicity.

Perhaps these declarations are already illegal, since no rule gives them a meaning. To clarify matters, I suggest in subclause 6.5.2.3 appending to page 62, line 35:

A type specifier of the form

enum identifier

shall not occur prior to the end of the enumerator-list that defines the content.

If this sentence is not appended, something like it should appear as a footnote.

Comment from WG14 on 1997-09-23:

Correction

Add to subclause 6.5.2.3, page 63, another Example:

An enumeration type is compatible with some integral type. An implementation may delay the choice of which integral type until all enumeration constants have been seen. Thus in:

enum f { c = sizeof(enum f) };

the behavior is undefined since the size of the respective enumeration type is not necessarily known when sizeof