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https://issues.apache.org/jira/browse/MESOS-2756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14605356#comment-14605356
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Bernd Mathiske commented on MESOS-2756:
---------------------------------------
[~benjaminhindman]] The class Base in the example code directly above does have
a public default copy constructor. Just protecting the argument-less default
constructor is insufficient. Writing the class this way avoids all object
slicing problems:
{code}
class Base {
public:
virtual int get() const { return v; }
protected:
Base(const Base& other) : v(base.v) {}
Base(int _v) : v(_v) {}
int v;
private:
Base() {}
};
{code}
See also the discussion between [~jvanremoortere] and me above. So, copy
constructors need to be addressed in the solution to this ticket, one way or
another!
> Update style guide: Avoid object slicing
> ----------------------------------------
>
> Key: MESOS-2756
> URL: https://issues.apache.org/jira/browse/MESOS-2756
> Project: Mesos
> Issue Type: Improvement
> Reporter: Joris Van Remoortere
> Assignee: Joris Van Remoortere
> Labels: c++, mesosphere
>
> In order to improve the safety of our code base, let's augment the style
> guide to:
> "Disallow public construction of base classes"
> so that we can avoid the object slicing problem. This is a good pattern to
> follow in general as it prevents subtle semantic bugs like the following:
> {code:title=ObjectSlicing.cpp|borderStyle=solid}
> #include <stdio.h>
> #include <vector>
> class Base {
> public:
> Base(int _v) : v(_v) {}
> virtual int get() const { return v; }
> protected:
> int v;
> };
> class Derived : public Base {
> public:
> Derived(int _v) : Base(_v) {}
> virtual int get() const { return v + 1; }
> };
> int main() {
> Base b(5);
> Derived d(5);
> std::vector<Base> vec;
> vec.push_back(b);
> vec.push_back(d);
> for (const auto& v : vec) {
> printf("[%d]\n", v.get());
> }
> }
> {code}
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