考虑这个类:
class Foo
{
public:
~ Foo ()
{
std::cout << "~Foo\n";
}
typedef std::vector<std::string> Words;
const Words & words ()
{
return m_words;
}
private:
Words m_words = {"foo", "bar", "baz"};
};
C++标准的第12.2节规定了临时对象的生命周期。我认为这应该没问题:
for (auto w : Foo () .words ())
std::cout << w << "\n";
但事实并非如此。
~Foo
terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_M_construct null not valid
[1] 10290 abort (core dumped) ./a.out
标准让我感到困惑。为什么在循环运行之前会调用
~Foo
?