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[C++] operator overloading and memory management.

c_wraith · 2001-12-17T11:43:55

Consider a class with overloaded arithmetic operators, following the immutable pattern. I seem to have embedded my question in the code: class Vector2d { private: double m_x, m_y; public: Vector2d(double x, double y) { m_x = x; m_y = y; } virtual ~Vector2d() {} double getX() { return m_x; } double getY() { return m_y; } const Vector2d& operator+ (const Vector2d& other) { // How do I do this without a memory leak? // // I get compiler warnings on this: return Vector2d(m_x + other.m_x, m_y + other.m_y); // The compiler warnings are obviously because I''m // returning a reference to a stack allocated // structure, which will get blown away on the next // function call. // // The only alternative I can think of is this: return *new Vector2d(m_x + other.m_x, m_y + other.m_y); // While the above compiles without warnings, it seems // like a memory leak. Does the compiler handle this // somehow, or is this a genuine memory leak? // // If it is a memory leak, what''s the correct solution // to this problem? } // other operators }

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Started by c_wraith December 13, 2001 12:47 PM

11 comments, last by c_wraith 22 years, 4 months ago

Kylotan

10,510

December 16, 2001 02:32 PM

null_pointer

289

December 16, 2001 06:11 PM

I thought that the const reference scoping rules only applied to function parameters, not return values, and only so that you could pass temporaries to functions expecting const references:

#include using std::string;void dosomething(const string& s){  // ...}int main(){  dosomething(string("hello"));  return 0;}

Stoffel

250

December 17, 2001 11:43 AM

quote:Original post by null_pointer
I thought that the const reference scoping rules only applied to function parameters, not return values, and only so that you could pass temporaries to functions expecting const references:

Not sure what you mean by "scoping rules", but I have member functions return objects by const reference all the time.

  class ConstSingleton{  ConstSingleton (); // private property, keep outpublic:  const ConstSingleton &getInstance () const  {    static ConstSingleton theObj;    return theObj;  }};

Doesn''t have to be singleton of course, but almost anywhere I return an object that''s guaranteed to exist, I return it by const reference. (If it might not exist, I return a pointer and return NULL when it doesn''t exist).

[C++] operator overloading and memory management.

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[C++] operator overloading and memory management.

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