c++ - 局部自动函数变量的销毁与返回值的构造之间的顺序

Question

存在依赖于本地自动函数变量在创建返回值后销毁的代码，例如:

1) Unmangling the result of std::type_info::name

std::string demangle(const char* name)
{
    int status = -4;
    std::unique_ptr<char, void(*)(void*)> res {
        abi::__cxa_demangle(name, NULL, NULL, &status),
        std::free
    };
    return (status==0) ? res.get() : name;
}

2) Timing of scope-based lock guards and return values

class C {
    mutable std::mutex _lock;
    map<string,string> deep_member;
public:
    auto get_big_lump()
    {
        std::unique_lock<std::mutex> lock(_lock);
        return deep_member;
    }
};

标准在哪里规定这个顺序是有保证的？

Answer 1

[stmt.return]/3 :

The copy-initialization of the result of the call is sequenced before the destruction of temporaries at the end of the full-expression established by the operand of the return statement, which, in turn, is sequenced before the destruction of local variables ([stmt.jump]) of the block enclosing the return statement.