https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83469
Bug ID: 83469
Summary: union is not accepted as a valid class-key in template
name resolution
Product: gcc
Version: 5.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: smw at gcc dot gnu.org
Target Milestone: ---
The following code is accepted by clang, icc, and msvc (all versions tested)
but is rejected with all version of GCC (tested from 4.0 though 7.1).
struct S {
union U { int m; };
};
template <typename T>
void f()
{ union T::U u; }
int
main()
{
f<S>();
}
The compilation error is as follows.
$ g++ -Wall -Wextra -pedantic -o tun tun.cpp
tun.cpp: In function ‘void f()’:
tun.cpp:7:14: error: ‘union’ tag used in naming ‘class T::U’ [-fpermissive]
{ union T::U u; }
^
tun.cpp:7:14: note: ‘class T::U’ was previously declared here
tun.cpp: In instantiation of ‘void f() [with T = S]’:
tun.cpp:12:8: required from here
Note that nothing in ISO/IEC 14882:2014 16.6/5 [temp.res] implies the class-key
'union' should be treated differently than the class-key 'struct' or 'class'
when resolving qualified names.
