https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78157
Bug ID: 78157
Summary: Incorrect diagnostic for variable template declaration
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: kfischer at college dot harvard.edu
Target Milestone: ---
Consider the following:
```
template <class S> class A {
template<class T, class U> static T pi;
};
template <> template <class T> double A<int>::pi<double, T> =
3.1415926535897932385;
extern template double A<int>::pi<double, int>;
template double A<int>::pi<double, int>;
```
GCC complains:
```
test2.cpp:4:47: error: conflicting declaration ‘double A<int>::pi<double, T>’
template <> template <class T> double A<int>::pi<double, T> =
3.1415926535897932385;
^~~~~~~~~~~~~
test2.cpp:2:39: note: previous declaration as ‘T A<int>::pi<T, U>’
template<class T, class U> static T pi;
^~
test2.cpp:4:47: error: got 1 template parameters for ‘T A<int>::pi<T, U>’
template <> template <class T> double A<int>::pi<double, T> =
3.1415926535897932385;
^~~~~~~~~~~~~
test2.cpp:4:47: error: but 2 required
test2.cpp: In instantiation of ‘double A<int>::pi<double, int>’:
test2.cpp:6:25: required from here
test2.cpp:6:25: error: explicit instantiation of ‘A<int>::pi<double, int>’ but
no definition available [-fpermissive]
template double A<int>::pi<double, int>;
^~~~~~~~~~~~~~~
```
Clang accepts this without error. ICC complains that the partial specialization
is
not allowed. I don't know whether or not this code is actually valid C++ or
not,
but either way, the diagnostic seems off, since there are two template
parameters
provided.
Godbolt links:
GCC 7: https://godbolt.org/g/W6OsWw
Clang: https://godbolt.org/g/3h8s93
