enums

[D. Hugh Redelmeier]

In article <1608 at dataio.Data-IO.COM> bright at Data-IO.COM (Walter Bright) writes:
>From reading the grammar for enums in the Ansi spec, it seems that the
>following is not allowed:
>
>	enum abc { };		/* empty member list	*/
>	enum def { b, };	/* trailing comma	*/
>
>Many compilers accept this, and I've run across code that uses it. Any
>thoughts? Is this an oversight in the spec?

I submitted a comment on the trailing comma during the first public
review period.  So it isn't an oversight, but I do think that it is
a mistake.  I am not sure how I feel about empty enums (perhaps a
good definition for void might be: "typedef void enum {};" :-).
Here is my comment:

Section 3.5.2.3, page 54, line 17 [of the then-current draft]

I think that an enumerator-list should be optionally terminated by a
comma.  This is analogous to the way an initializer is optionally
terminated by a comma (3.5.6 61 at 21).  The benefits are similar (a
terminator is less error-prone than a separator (consider Pascal's
semicolon)).

This is currently legal in the two compilers I use (the Ritchie
compiler (the original implementation of enum, so it should carry
some weight), and System V VAX UNIX PCC).  I do use the feature.

Hugh Redelmeier
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In desperation: hugh at csri.toronto.edu
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