http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60277
Bug ID: 60277
Summary: Bogus "inline function virtual ..." used but never
defined
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ppluzhnikov at google dot com
Test case:
struct Foo {
inline virtual void func() = 0;
};
struct Bar : public Foo {
void func() { }
};
int main()
{
Foo *f = new Bar;
f->func();
}
Using trunk:
g++ (GCC) 4.9.0 20140219 (experimental)
g++ -c -Wall -Wextra t.cc
t.cc:2:23: warning: inline function 'virtual void Foo::func()' used but never
defined
inline virtual void func() = 0;
^
But Foo::func is never actually used.
Analysis by Nick Lewycky:
The relevant [basic.odr]/2 text is:
"A virtual member function is odr-used if it is not pure. A non-overloaded
function whose name appears as a potentially-evaluated expression or a member
of a set of candidate functions, if selected by overload resolution when
referred to from a potentially-evaluated expression, is odr-used, unless it is
a pure virtual function and its name is not explicitly qualified."
Since the function isn't ODR-used, there's no need for it to have a definition:
"An inline function shall be deļ¬ned in every translation unit in which it is
odr-used." [basic.odr]/3
