A20-8-3 - Unofficial Autosar C++ Guidelines Reference

Rule A20-8-3 (required, implementation, automated)

A std::shared_ptr shall be used to represent shared ownership.

Rationale

allows to retain shared ownership by keeping multiple std::shared_ptr instances pointing at the same object. The object is removed when the last std ::shared_ptr instance goes out of scope. Although reference counting mechanism included brings some overhead over a raw pointer, it clearly states ownership status of the object and effectively prevents from possible memory leaks. std::shared_ptr

Example

// $Id: A20-8-3.cpp 308507 2018-02-21 13:23:57Z michal.szczepankiewicz $

#include <memory>
#include <cstdint>
#include <thread>

struct A
{
A(std::uint8_t xx, std::uint8_t yy) : x(xx), y(yy) {}
std::uint8_t x;
std::uint8_t y;
};

void Foo(A* obj) { }
void Bar(A* obj) { }

void Foo2(std::shared_ptr<A> obj) { }
void Bar2(std::shared_ptr<A> obj) { }

int main(void)
{
A* a = new A(3,5); //non-compliant with A18-5-2

std::shared_ptr<A> spA = std::make_shared<A>(3,5);

//non-compliant, not clear who is responsible
//for deleting object a
std::thread th1{&Foo, a};
std::thread th2{&Bar, a};

//compliant, object spA gets deleted
//when last shared_ptr gets destructed
std::thread th3{&Foo2, spA};
std::thread th4{&Bar2, spA};

th1.join();
th2.join();
th3.join();
th4.join();

return 0;
}

Unofficial Autosar C++ Guidelines Reference

Rationale

Example

See also