https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101222
Bug ID: 101222
Summary: unwanted templated constructor instantiation due to
wrong binary operator access
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: vopl at bk dot ru
Target Milestone: ---
cat main.cpp && echo EOFFFFFF
template<typename T> struct Trap {};
struct Some
{
template<typename T, int = sizeof(Trap<T>)> Some(T) {}// Trap for T - only
for check if Some<T> was instantiated
};
void operator<(const Some&, const Some&);//wrong instantiatoion of
Some::Some<E> here
enum E{};
int main()
{
bool b = E{} < E{};// wrong access to "bool operator<(const Some&, const
Some&);"
return 0;
}
template <> struct Trap<E> {};// now check Trap for E
EOFFFFFF
$ g++ -c main.cpp
main.cpp:17:20: error: specialization of 'Trap<E>' after instantiation
17 | template <> struct Trap<E> {};// now check Trap for E
| ^~~~~~~
main.cpp:17:20: error: redefinition of 'struct Trap<E>'
main.cpp:1:29: note: previous definition of 'struct Trap<E>'
1 | template<typename T> struct Trap {};
| ^~~~
-------------------------------------------------
In these code "void operator<(const Some&, const Some&)" is not a candidate for
overloading for "E{} < E{}", so, it must not be used at all, and as a result,
Some::Some<E> must not be instantiated.
All gcc versions with c++11 standard are affected. Clang and msvc are okay.
