[comp.lang.c++] scope of enumerators

schwarze@isaak.isa.de (Jochen Schwarze) (11/09/89)

Consider the following:

    struct color {
	enum { red, green, blue }   type;
    };

    main()
    {
	struct color favourite;

	favourite.type = red;
    }

If this piece of code is compiled with g++ (1.35.0) or AT&T cfront (1.20)
both compilers complain about `red' in line 10 being undefined or
undeclared, resp.

gcc (1.35.0) and Sun cc compile without problems.

The C++ book by Stroustrup says nothing about an enumerators scope
being restricted.

Is this a compiler bug or a difference between c and c++?

Thanks in advance.

Jochen Schwarze                     Domain: schwarze@isaak.isa.de
ISA GmbH, Stuttgart, West Germany   UUCP:   schwarze@isaak.uucp
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thant@horus.sgi.com (Thant Tessman) (11/14/89)

In article <2113@isaak.isa.de>, schwarze@isaak.isa.de (Jochen Schwarze) writes:
> 
> Consider the following:
> 
>     struct color {
> 	enum { red, green, blue }   type;
>     };
> 
>     main()
>     {
> 	struct color favourite;
> 
> 	favourite.type = red;
>     }
> 
> If this piece of code is compiled with g++ (1.35.0) or AT&T cfront (1.20)
> both compilers complain about `red' in line 10 being undefined or
> undeclared, resp.
> 
> gcc (1.35.0) and Sun cc compile without problems.
> 

In _Programming in C++_ by Dewhurst and Stark, on page 60 it mentions 
that 'enum' can be nested within a class.  Although it doesn't outright say
it, I would think that this implies that 'enum' scopes like anything else.

I have used 'enum' this way (i.e. assuming it scopes) and I find it very
usefull 
for making code more readable (and more typesafe, because C++ (2.0) actually
typechecks enums as separate types).

I would think gcc and Sun cc are busted.

thant

There are 336 dimples on the standard golf ball.

hansen@pegasus.ATT.COM (Tony L. Hansen) (11/16/89)

<> Consider the following:
<>     struct color {
<> 	enum { red, green, blue }   type;
<>     };
<>     main() {
<> 	struct color favourite;
<> 	favourite.type = red;
<>     }
<> If this piece of code is compiled with g++ (1.35.0) or AT&T cfront (1.20)
<> both compilers complain about `red' in line 10 being undefined or
<> undeclared, resp.  gcc (1.35.0) and Sun cc compile without problems.

< I have used 'enum' this way (i.e. assuming it scopes) and I find it very
< useful for making code more readable (and more typesafe, because C++ (2.0)
< actually typechecks enums as separate types). I would think gcc and Sun cc
< are busted.

This is one of the few places where C++ is not a superset of C. In C++, the
scope of the enum is restricted to the class; in C, the enum has the same
scope as the structure.

Gcc and Sun cc aren't broken; they're doing exactly what they're supposed to
do.

					Tony Hansen
				att!pegasus!hansen, attmail!tony
				    hansen@pegasus.att.com