Destruction order in C++

Question

#include <iostream>
class X{
public:
    X(int n = 0) : n(n) {}
    ~X() {std::cout << n;}
    int n;
};
void main()
{
    X a(1);
    const X b(2);
    static X c(3);
}

Output is 213, I thought the destructor uses a LIPO stack, so why it doesn't destruct in a reverse order 321?

I'm pretty confused and I'd like to know more about it. Thank you so much.

[Covered in documentation](https://en.cppreference.com/w/cpp/language/storage_duration). Skip down to the paragraph on static storage duration. — user4581301, Feb 27 '19 at 00:59

score 3 · Accepted Answer · answered Feb 27 '19 at 00:59

3

a and b are of automatic duration, destroyed when the block ends. c is of static duration, destroyed when the program terminates. LIFO order only applies to objects destroyed at the same point in the program.

answered Feb 27 '19 at 00:59

Igor Tandetnik

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score 1 · Answer 2 · answered Feb 27 '19 at 00:59

It is calling the destructors in reverse order, but a static variable has a different lifetime.

See Does C++ call destructors for global and class static variables? which explains that variables with a global lifetime are destructed sometime after main returns.

score 1 · Answer 3 · answered Feb 27 '19 at 01:00

1

That is LIFO. a and b are destructed in reverse order when main returns, c is destructed at some undetermined point between when main returns and the program actually exits (because it's static, tied to the lifetime of the program, not main itself).

answered Feb 27 '19 at 01:00

ShadowRanger

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Destruction order in C++

3 Answers3