Path: utzoo!attcan!uunet!lll-winken!ames!pasteur!ucbvax!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!rutgers!att!ulysses!andante!alice!debra
From: debra@alice.UUCP (Paul De Bra)
Newsgroups: comp.unix.questions
Subject: Re: Illegal union question
Message-ID: <8968@alice.UUCP>
Date: 25 Feb 89 20:26:09 GMT
References: <833@wzlr.UUCP>
Reply-To: debra@alice.UUCP ()
Organization: AT&T, Bell Labs
Lines: 37

In article <833@wzlr.UUCP> jms@wzlr.UUCP (Jack Stephens) writes:
>
>The following declaration yeilds an "illegal member use" error
>for both f and next under the compilers on both by PC and my 3B1 
>and I can't seem to understand why.  Amybody feel pedegogical ?
>
>jms
>
>typedef struct m_i {
>  int type;
>	 union {
>	 int (*f)();
>	 struct m_i *next;
>	 }
>} menu[10];

Aha, different compilers have a different opinion on this one.
First of all, whether the definition is correct or not, the union needs
a name, thus
	union {
	...
	} name_of_union;

This is a nuisance because one must access fields like
mymenu[5].name_of_union.next instead of mymenu[5].next
However, one can have several unions inside the same struct, and such a
union may have fields with names that also appear in some other union.

Some compilers accept your declaration, some others want at least a ';'
after the } that ends the union, but in either case there is no way to
access the fields of the union by name.

Paul.
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