检测到临时的悬挂引用

Clang 3.9非常重用临时用户使用的内存。

Clang 3.9 extremely reuses memory used by temporaries.

此代码为UB（简化代码）：

This code is UB (simplified code):

template <class T>
class my_optional
{
public:
    bool has{ false };
    T value;

    const T& get_or_default(const T& def)
    {
        return has ? value : def;
    }
};

void use(const std::string& s)
{
    // ...
}

int main()
{
    my_optional<std::string> m;
    // ...
    const std::string& s = m.get_or_default("default value");
    use(s); // s is dangling if default returned
}

我们有大量类似上面的代码（ my_optional 只是一个简单的示例来说明它。）

We have tons of code something like above (my_optional is just a simple example to illustrate it).

由于UB从3.9开始，所有clang编译器重用此内存，这是合法行为。

Because of UB all clang compiler since 3.9 starts to reuse this memory, and it is lawful behavior.

问题是：如何在编译时或使用消毒剂之类的检测此类悬挂引用在运行时？没有clang消毒剂可以检测到它们。

The question is: how to detect such dangling references at compile time or with something like sanitizer at runtime? No clang sanitizer can detect them.

已更新。请不要回答：使用 std :: optional 。请仔细阅读：问题不在于此。

Upd2。请不要回答：您的代码设计不好。仔细阅读：问题与代码设计无关。

Upd. Please do not answer: "use std::optional". Read carefully: question is NOT about it.
Upd2. Please do not answer: "your code design is bad". Read carefully: question is NOT about code design.