未分配的delete []指针未分配

Question

I am using the new operator to create a dynamically allocated array (I am using this one because I want to save on the memory overhead of using a vector). The error occurs in the destructor, saying the pointer being freed was not allocated although obviously it was. The constructors and destructors are as follows:

~Path() {
    printf("Path Destructor\n");
    if(points) {
        delete[] points;
    }
}
Path(const std::vector<PathPoint>& points_) {
    size = points_.size();
    points = new PathPoint[size];
    int i = 0;
    for(const PathPoint& p : points_) {
        points[i++] = p;
    }
    printf("Path created\n");
}

Answer 1

You have to apply The Rule of Three :

The C++ standard says that :

The implicitly-defined copy constructor for a non-union class X performs a memberwise copy of its subobjects. [n3126.pdf section 12.8 §16]

The implicitly-defined copy assignment operator for a non-union class X performs memberwise copy assignment of its subobjects. [n3126.pdf section 12.8 §30]

So the implicitly-defined copy constructor and copy assignment operator for your Path class will not call new[] for you.

Define a copy constructor and a copy assignment oerator that perform the required allocation.

---

Note:

• You can also make your type non copyable, declare them without definition :

Eg :

 Path( const Path& other );      // non construction-copyable
 Path& operator=( const Path& ); // non copyable

(or use boost::noncopyable )

• The typical overhead of a std::vector<> is very very low, there are few contexts where it really matters : use it as much as you can to avoid such problems.