Are enums safe to use in portable code?

[Stanley Friesen]

In article <ENAG.91Feb1003707 at hild.ifi.uio.no> enag at ifi.uio.no (Erik Naggum) writes:
>Assume these definitions:
 
>	enum { frotz, klutz } foo;					[1]
>	enum { gunk, junk } bar;					[2]
> ...
>The declaration in [1] declares a distinct (anonymous) type of which
>foo is an object.  Likewise [2] declares another distinct (anonymous)
>type of which bare is an object.

So far so good. ANSI does indeed specify that each enumeration is a distinct
type.

> frotz and klutz [1] are names of
>constant values of the type of object of which foo is an instance.
>Likewise for gunk and junk [2].

However here you deviate from the ANSI standard.
According to 3.5.2.2 (Semantics):
"The identifiers in an enumerator list are declared as constants that
have type int and may appear anywhere such are permitted".

Thus frotz, klutz, gunk, and junk are all *int's*, and may be used anywhere
an int may be used.  This includes *all* forms of comparison, thus:

    (klutz == gunk)

is a perfectly valid ANSI C construct, and evaluates to true if and only if
the value of klutz equals the value of gunk.  (This is also a constant
expression, that can be evaluated wholly by the compiler)

Any C compiler that fails to accept this is *not* ANSI C.  (It may be
a valid pre-ANSI compiler though).
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uunet!tdatirv!sarima				(Stanley Friesen)