Is extending a base class with non-virtual destructor dangerous in C++
- by Akusete
Take the following code
class A {
};
class B : public A {
};
class C : public A {
int x;
};
int main (int argc, char** argv) {
A* b = new B();
A* c = new C();
//in both cases, only ~A() is called, not ~B() or ~C()
delete b; //is this ok?
delete c; //does this line leak memory?
return 0;
}
when calling delete on a class with a non-virtual destructor with member functions (like class C), can the memory allocator tell what the proper size of the object is? If not, is memory leaked?
Secondly, if the class has no member functions, and no explicit destructor behaviour (like class B), is everything ok?
I ask this because I wanted to create a class to extend std::string, (which I know is not recommended, but for the sake of the discussion just bear with it), and overload the +=,+ operator. -Weffc++ gives me a warning because std::string has a non virtual destructor, but does it matter if the sub-class has no members and does not need to do anything in its destructor?
-- FYI the += overload was to do proper file path formatting, so the path class could be used like
class path : public std::string {
//... overload, +=, +
//... add last_path_component, remove_path_component, ext, etc...
};
path foo = "/some/file/path";
foo = foo + "filename.txt";
//and so on...
I just wanted to make sure someone doing this
path* foo = new path();
std::string* bar = foo;
delete bar;
would not cause any problems with memory allocation
