Haha alright

doesn't make any difference. std::move is basically just a cast, you're still returning the reference to a local object. hence Danling reference

So after returning a lvalue reference to local won't cause any undefined behavior!!!

dangling reference will likely cause undefined behavior

Cuz it won't cause undefined behavior

@BOND_0O7 no, I meant rvalue references. A rvalue reference does not increase the lifetime of an object. Why should you not write std::string& avoid() { return std::string("hello"); } ? For the same reasong you should not write std::string&& avoid2() { return std::string("hello"); } either

I think it must return a const lvalue in case of returning lvalue reference

please provide a full comileable example. A const value will change nothing here.

none

std::string func() { std::string name{"qwerty"}; return name; } std::string result = func() - here copy constructor std::string&& result = func() - here nothing?

the second one will not trigger an constructor or assignment operator call. This is basically like std::string * ptr = &otherString;. Which operator/constructor should be called?

std::string func() { std::string name{"qwerty"}; return name; } std::string result = func() - here copy constructor std::string&& result = func() - here nothing?

For the first thing there are basically multiple options and multiple things to consider. Compiler nowadays are likely to neither copy assign nor copy construct. Changes to C++17 regarding RVO also make it likely the compiler is trying to avoid any "unecessary" object instantiation.

But if I disable all optimization? It will call copy constructor?

Even without I am unaware of any compiler that calls the copy ctor here

Thank you for explaining)

sure. You can read more about RVO/NRVO/Copy Ellision here https://en.cppreference.com/w/cpp/language/copy_elision

Hey which app is best for learning html

Actually I am a beginner in C

Actually I am a beginner in C

😂😂 its just like array

I didn't understand

Why?

Why this?

Why this?

Are you asking us?

Yes

¯\_(ツ)_/¯

Sorry, but I see no connection from your code to what the gif conveyed.

How is it related to passing values by reference?

Why this?

Did you die?

Actually I can't understand yet that why it can't run

But the fact is, it doesn’t

Means

too many topics mixed here (

😂😂 lol you just act like bot you will recognize everything...

Am a beginner in c++ and am confused about "using namespace std;" how do I differentiate when to use it

Am a beginner in c++ and am confused about "using namespace std;" how do I differentiate when to use it

Am a beginner in c++ and am confused about "using namespace std;" how do I differentiate when to use it