gdb/lldb C++类的虚析构函数在虚函数表的数目为2？

gdb/lldb C++类的虚析构函数在虚函数表的数目为2？

#include <iostream>class A {public:        A() { std::cout << "A()" << std::endl;  }        virtual ~A() { }};int main(void){        A a;        return 0;}

lldb 调试：lldb-340.4.119

(lldb) expr -G a -- (*(void ***)&a)[0]

(void *) $1 = 0x0000000100000ed0 a.out`A::~A() at destructor.cpp:6
(lldb) expr -G a -- (*(void ***)&a)[1]
(void *) $2 = 0x00000001000010b0 a.out`A::~A() at destructor.cpp:6

gdb调试：GNU gdb (GDB) Fedora 7.9.1-20.fc22

(gdb) p /a (*(void ***)&a)[0]
$2 = 0x4009f0 <A::~A()>
(gdb) p /a (*(void ***)&a)[1]
$3 = 0x400a20 <A::~A()>