How do lambda captures work in C++?

Capture	Meaning
[x]	x by value
[&x]	x by reference
[=]	All used variables by value
[&]	All used variables by reference
[this]	The current object pointer
[x = std::move(y)]	Init capture (C++14): create a member

#include <iostream>
#include <memory>

int main() {
    int a = 1, b = 2;
    auto f = [a, &b] { b += a; return b; };
    std::cout << f() << ' ' << b << '\n';

    auto p = std::make_unique<int>(7);
    auto g = [q = std::move(p)] { return *q; };        // move into the lambda
    std::cout << g() << ' ' << (p == nullptr) << '\n';
}

A lambda which is saved or returned must not capture local variables by reference, because the variables are destroyed. See Lambda Expressions.

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