On Sun, 19 May 2024, Martin Uecker wrote:
> c23 specifies that the type of a redeclared enumerator is the one of the
> previous declaration. Convert initializers with different type
> accordingly
> and add -Woverflow warning.
It doesn't make sense to use -Woverflow. Either the value is the same (in
which case it fits in the desired type), or it's different (and you should
get the "conflicting redeclaration of enumerator" error or some equivalent
error, whether or not the value in the redeclaration fits in the previous
type).
Note that this includes both explicit values and values determined by
adding 1 implicitly. E.g.
enum e { A = 0, B = UINT_MAX };
enum e { B = UINT_MAX, A };
is not valid, because in the redefinition, A gets the value 1 greater than
UINT_MAX (which is not representable in unsigned int) - there is *not* an
addition in type unsigned int, or in type enum e.
The constraint violated is the general one "If an identifier has no
linkage, there shall be no more than one declaration of the identifier (in
a declarator or type specifier) with the same scope and in the same name
space, except that: ... enumeration constants and tags may be redeclared
as specified in 6.7.3.3 and 6.7.3.4, respectively." (where 6.7.3.3 says
"Enumeration constants can be redefined in the same scope with the same
value as part of a redeclaration of the same enumerated type." - as the
redefinition is not with the same value, the "as specified in 6.7.3.3" is
not satisfied and so the general constraint against redeclarations with no
linkage applies).
--
Joseph S. Myers
[email protected]
