I'm getting the following error during compilation:

Severity    Code    Description Project File    Line    Suppression State
Error   C2664   'mytest::Test::Test(const mytest::Test &)': cannot convert argument 1 from '_Ty' to 'const mytest::Test &'  TotalTest   C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30037\include\xutility    158

I have no idea what is, so I'm putting the code here to exemplify what was being done:

TotalTest.cpp

include <iostream>

#include "Test.h"

using namespace mytest;

int main()
{
    std::cout << "Hello World!\n";

    new Test();
}

Test.h

#pragma once
#include "Test.h"
#include <iostream>

namespace mytest
{
    using namespace std;

    class Test
    {
    public:
        Test();
        ~Test();

        shared_ptr<Test> t;

    };
}

Test.cpp

#include "Test.h"

namespace mytest
{

    Test::Test()
    {
    }

    Test::~Test()
    {
    }

}

TestFactory.h

#pragma once

#include "Test.h"
#include <iostream>

namespace mytest
{
    using namespace std;

    class TestFactory
    {
    public:
        TestFactory();

        shared_ptr<Test> CreateTest(int testClass);
    };

}

TestFactory.cpp

#include "TestFactory.h"

namespace mytest 
{
    TestFactory::TestFactory()
    {
    }

    shared_ptr<Test> TestFactory::CreateTest(int testClass)
    {
        return make_shared<Test>(new Test());
    }
}

I'm using Visual Studio C language standard: ISO C 14 Standard (/std:c 14)

CodePudding user response：

In TestFactory::CreateTest(), make_shared<Test>(new Test()) is wrong, as Test does not have a constructor that accepts a Test* pointer as input.

You need to use make_shared<Test>() instead, letting make_shared() call the default Test() constructor for you:

shared_ptr<Test> TestFactory::CreateTest(int testClass)
{
    return make_shared<Test>();
}

Any parameters you pass to make_shared() are passed to the constructor of the type specified in the template argument. In this case, there are no parameters needed.

CodePudding user response：

The error comes from the following line:

return make_shared<Test>(new Test());

There are 2 ways of initializing a std::shared_ptr:

1. Using the std::shared_ptr constructor directly, which requires you to pass a Test object already allocated on the heap, e.g.:

    std::shared_ptr<Test> p{ new Test() };
   

2. Using make_shared(), which performs the heap allocation internally, e.g.:

    std::shared_ptr<Test> p{ std::make_shared<Test>() };
   

   Where in the parentheses you can pass parameters to the constructor of Test.

The 2nd option is usually prefered. You can see more info here: Difference in make_shared and normal shared_ptr in C

In addition:

1. Test.h should not include itself (it has #include "Test.h" at the top).

2. You should avoid using using namespace std;. More info here: Why is "using namespace std;" considered bad practice?