LegacySinkAndUniquePtr.cpp

// compile at https://godbolt.org/g/yb47Aq
//

#include <iostream>
#include <memory>

class Widget
{
  public:
  	void DoStuff() { }
};

void PrintError() { }

bool LegacySink(Widget *pWidget, int a) // owns widget on success
{
  if (a == 0)
    return false;
  
  delete pWidget;
  return true;
}

void TestOld()
{
  Widget * pW1 = new Widget();
  Widget * pW2 = new Widget();
  Widget * pW3 = new Widget();
  
  if (!LegacySink(pW1, 1))
  {
    delete pW1;
    delete pW2;
    delete pW3;
    PrintError();
    return;
  }
  
  if (!LegacySink(pW2, 1))
  {
    // delete pW1; // not needed, already in sink!
    delete pW2;
    delete pW3;
    PrintError();
    return;
  }
  
  if (!LegacySink(pW3, 1))
  {
    // delete pW1; // not needed, already in sink!
    // delete pW2; // not needed, already in sink
    delete pW3;
    PrintError();
    return;
  }
}

void TestOldImproved()
{
  // one
  Widget * pW1 = new Widget();
  
  if (!LegacySink(pW1, 1))
  {
    delete pW1;
    PrintError();
    return;
  }
  
  // two
  Widget * pW2 = new Widget();
  
  if (!LegacySink(pW2, 1))
  {
    delete pW2;
    PrintError();
    return;
  }
  
  // three
  Widget * pW3 = new Widget();
  
  if (!LegacySink(pW3, 1))
  {
    delete pW3;
    PrintError();
    return;
  }
}

void TestNew()
{
  // one
  auto pW1 = std::make_unique<Widget>();
  
  if (!LegacySink(pW1.get(), 1))
  {
    PrintError();
    return;
  }
  
  // two
  auto pW2 = std::make_unique<Widget>();
  
  if (!LegacySink(pW2.get(), 1))
  {
    PrintError();
    return;
  }
  
  // three
  auto pW3 = std::make_unique<Widget>();
  
  if (!LegacySink(pW3.get(), 1))
  {
    PrintError();
    return;
  }
}

int main()
{
  TestOld();
  TestOldImproved();
  TestNew();
  return 0;
}