Re: Arrays of Objects
On Wed, 31 Oct 2007 17:35:57 CST, Tjark Weber <tjark.weber@gmail.com>
wrote:
Hi,
I shamelessly took the following example from the "C++ FQA" that was
posted earlier, and I would assume it's well-known in this group.
class A { public: int a; };
class B : public A { public: int b; };
A * p = new B[10];
p[5].a = 1;
On my system, memory for integers 0..19 is allocated, and integer 5 is
assigned the value 1 (rather than integer ... umm ... 10, I guess).
What does the C++ standard have to say about this code? Does it
invoke undefined behavior? Is the behavior completely specified, and
bound to be as on my system? Or could the compiler be smart enough to
"get this right"?
Tjark
AFAIK, according to the standard it is legal code. However, please
read Scott Meyers: "More Effective C++", Item 3 ("Never treat arrays
polymorphically").
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