C++ Stack-allocated object assignment and destructor call

Question

I'm trying to understand what appears to be some weird behaviour when assigning a new value to an object allocated on stack (the destructor gets called twice for the same data set). I'll just start with the code snippet and its output: ``` class Foo { public: Foo(const string& name) : m_name(name) { log("constructor"); } ~Foo() { log("destructor"); } void hello() { log("hello"); } private: string m_name; void log(const string& msg) { cout << "Foo." << this << " [" << m_name << "] " << msg << endl; } }; int main() { { Foo f {"f1"}; f.hello(); f = Foo {"f2"}; f.hello(); } cout << "scope end" << endl; } ``` Output: ``` Foo.0x7fff58c66a58 [f1] constructor Foo.0x7fff58c66a58 [f1] hello Foo.0x7fff58c66a18 [f2] constructor Foo.0x7fff58c66a18 [f2] destructor Foo.0x7fff58c66a58 [f2] hello Foo.0x7fff58c66a58 [f2] destructor scope end ``` What I expected to happen: - 0x...58 gets created/initialised on stack - 0x...18 gets created/initialised on stack - Foo destructor gets called on 0x...58 (wit…

Accepted Answer

Your instance f is being assigned a copy of Foo {"f2"}, it's not a new construction.

Add the following operator= override to illustrate what is actually happening.

```
Foo& Foo::operator=(const Foo& other) {
    cout << "Foo::operator=(const Foo& other)" << endl;
    m_name = other.m_name;  
    return *this;
}
```

C++ Stack-allocated object assignment and destructor call

Solution

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