Sometimes, we know nothing about lifetime of lambda that captures an object state (e.g. return it from object, register it as a callback without ability to unsubscribe etc.). How to make sure that the lambda won't access already destroyed object on invocation?
#include <iostream>
#include <memory>
#include <string>
class Foo {
public:
Foo(const std::string& i_name) : name(i_name) {}
std::function<void()> GetPrinter() {
return [this]() {
std::cout << name << std::endl;
};
}
std::string name;
};
int main() {
std::function<void()> f;
{
auto foo = std::make_shared<Foo>("OK");
f = foo->GetPrinter();
}
auto foo = std::make_shared<Foo>("WRONG");
f();
return 0;
}
This program prints "WRONG" instead of "OK" (http://ideone.com/Srp7RC) just by coincidence (it seems it just reused the same memory for the second Foo
object). Anyway, this is a wrong program. First Foo
object is already dead when we execute f
.
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