Re: New failing in constructor
In article
<4b60b625-2b96-44ec-8c0a-ea8043c17b7a@a18g2000yqc.googlegroups.com>,
MC <manan.chopra@gmail.com> wrote:
Say I have the following classes
class A{};
class B{};
class C{};
class X{
A* a;
B* b;
C* c;
public:
X() : a(new A), b(new B), c(new C) {}
};
Say now new fails while initializing C. Since X is not constructed
completely it will not call its destructor and we will have a and b
never destructed and hence a memory leak.
What is the best way to avoid this problem.
Should I never use new in the constructor?
It's OK to use new in the constructor, but you have to make sure that it
will be deleted if something goes wrong. Using new in initializer lists
can be a problem. Although you can wrap the list in a try...catch block,
that doesn't help much when you have three objects getting newed like
you have. The obvious solution would be something like:
X::X(): a(0), b(0), c(0) {
try {
a = new A;
b = new B;
c = new C;
}
catch (...) {
delete a;
delete b;
delete c;
}
}
Depending on how you implement copy construction/assignment for the
class, another option may be to use auto_ptrs for the three objects.
class X {
auto_ptr<A> a;
auto_ptr<B> b;
auto_ptr<C> c;
public:
X() : a(new A), b(new B), c(new C) { }
};
If one of the news throws, the auto_ptrs that were initialized
successfully will delete what they own, but now X objects can't share
their object when copied.
Using a more sophisticated smart pointer can solve the sharing issue and
take care of destruction too!
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