https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107492
Bug ID: 107492
Summary: Unhelpful -Wignored-qualifiers warning in template
specialization
Product: gcc
Version: 12.2.1
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
GCC warns about this with -Wextra:
template<typename T> struct S { };
template<> struct S<void(*)()> { };
template<> struct S<const void(*)()> { };
template<typename T, typename U> constexpr bool is_same_v = false;
template<typename T> constexpr bool is_same_v<T, T> = true;
static_assert( ! is_same_v< void(*)(), const void(*)() > );
spec.cc:3:21: warning: type qualifiers ignored on function return type
[-Wignored-qualifiers]
3 | template<> struct S<const void(*)()> { };
| ^~~~~
spec.cc:8:40: warning: type qualifiers ignored on function return type
[-Wignored-qualifiers]
8 | static_assert( ! is_same_v< void(*)(), const void(*)() > );
| ^~~~~
The warning is wrong, the qualifiers are not ignored here. The two types are
distinct, as shown by the fact that the explicit specializations are not
redefinitions of each other, and the static assert passes.
