Issue 0013.03: What is the composite type of an enumeration and an integer?

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: Closed
Cross-references: 0127
Converted from: dr.htm, dr_013.html

Composite type of enum vs. integer not defined

There is one case where two types are compatible, but their composite type is not defined. To fix this problem, in subclause 6.1.2.6 insert after page 25, line 17:

- If one type is an enumeration and the other is an integer type, the composite type is the enumeration.

There may be other cases where “compatible” is not defined. I made a cursory search and did not find any.

Comment from WG14 on 1997-09-23:

Response

The issue is that in

enum {r,w,b} x;

and

some-int-type x;

where some-int-type happens to be the type that by subclause 6.5.2.2, page 61, line 40 is compatible with the type of the enum, what is the resultant composite type?

Subclause 6.1.2.6 on page 25, lines 11-12 says “a type that ... satisfies the following conditions” (added emphasis on “a”). The composite type of two compatible types is not necessarily unique. In this case both the enum type and the some-int-type satisfy the definition of “composite” type. This refutes the claim that the “composite type is not defined;” the point is that the standard does not guarantee a unique composite type.

As an example, in the following declarations:

enum {r, w, b} x;
 some_int_type x;

provided the enumeration type is compatible with the type of some_int_typ e, it is unspecified whether the composite type of x is the enumeration type or some_int_type.