https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61457
Bug ID: 61457
Summary: Inaccurately refusing non-ODR usage of type with no
linkage
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: filip.roseen at gmail dot com
Created attachment 32912
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=32912&action=edit
testcase.cpp
enum { X };
struct A { static constexpr auto val = X; };
int main () {
int x = A::val;
}
-------------------------
`gcc` is inaccurately rejecting `testcase.cpp` with the following diagnostic:
> testcase.cpp:3:34: error: ‘constexpr const<anonymous enum> A::val’, declared
> using anonymous type, is used but never defined [-fpermissive]
> struct A { static constexpr auto val = X; };
> ^
-------------------------
A detailed answer was provided by me at
http://stackoverflow.com/a/24019645/1090079
It is stated that an unnamed enum has no linkage in [basic.link]p8, but we must
also remember the following which is also stated in [basic.link]p8:
> A type without linkage shall not be used as the type of a variable
> or function with external linkage unless:
> - the entity has C language linkage (7.5), or
> - the entity is declared within an unnamed namespace (7.3.1), or
> - the entity is not odr-used (3.2) or is defined in the same translation
unit
----------------------------
`clang` correctly accepts the snippet.
