[Moved to DR at the September, 2013 meeting.]

Proposed resolution (August, 2013):

Change 9.7.1 [dcl.enum] paragraph 5 as follows:

...If the underlying type is not fixed, the type of each enumerator is the type of its initializing value:

• If an initializer is specified for an enumerator...

• If no initializer is specified for the first enumerator, the initializing value has an unspecified signed integral type.

• Otherwise...

In an enumeration whose underlying type is not fixed, the type of the first enumerator is unspecified if it has no initializer, meaning that an implementation could choose either a signed or an unsigned type. As a result, the values of one and two in this example could be either -1 and 0 or very large unsigned numbers:

  enum { zero, one = zero -1, two };

It would be better if 9.7.1 [dcl.enum] paragraph 5 specified the type of the first enumerator as a signed type.