https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67650
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2018-05-03 00:00:00 |2019-2-26
--- Comment #34 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Honza, could you take another look at this reduced version please?
__attribute__((weak)) void f() { }
template <typename T>
struct Base
{
virtual void virt() = 0;
void do_virt() { virt(); }
};
template <typename T>
struct Derived : Base<T>
{
void virt() {}
};
template <typename T>
struct Wrap
{
T* p = nullptr;
virtual void indirect_virt()
{
#ifdef FIX
p->virt(); // OK
#else
p->do_virt(); // link error
#endif
}
};
template <const char*>
struct Template
{
};
constexpr char str[] = "";
struct I
{
I() { f(); }
Wrap<Derived<Template<str>>> l;
};
int main(){new I();}
This is valid C++, but when compiled with -O1 -fdevirtualize it fails with:
l.cc:13:8: warning: ‘void Derived<T>::virt() [with T = Template<(& str)>]’ used
but never defined
void virt() {}
^~~~
/usr/bin/ld: /tmp/ccYAFtTY.o: in function `Wrap<Derived<Template<&str> >
>::indirect_virt()':
l.cc:(.text+0x57): undefined reference to `Derived<Template<&str> >::virt()'
collect2: error: ld returned 1 exit status
If compiled with -DFIX it links OK.
Even though the Template<(&str)> template argument is completely unused, it
compiles fine if Derived<int> is used instead, or
Derived<AnotherTemplate<int>>. It only fails when using a template that has a
pointer for its template parameter.
