Re: Protecting against uninitialized variables
On Mar 20, 12:48 am, "Tim Conkling" <tconkl...@gmail.com> wrote:
On Mar 19, 3:22 pm, Greg Herlihy <gre...@pacbell.net> wrote:
In my view this solution is over-engineered - it goes far beyond what is
required to ensure the zero-initialization of a fundamental type serving as
a class member.
Thanks, Greg. I wasn't aware that it was possible to default-
initialize the fundamental types. How does this look as a revised
implementation?
template <class T>
struct safe_type
{
safe_type() : m_val(T()) {}
safe_type(T val) : m_val(val) {}
T& operator=(T val) { m_val = val; return *this; }
operator T&() { return m_val; }
operator const T&() const { return m_val; }
T operator->() const { return m_val; }
private:
T m_val;
};
I think that the scale of this implementation is now proportionate to
the scope of the problem it addresses. One small suggestion about the
const T conversion operator: since fundamental types typically fit in
registers, it is usually more efficient to pass them by value instead
of by reference (see safe_type's constructor declaration for example).
So I would change the "operator const T&() const" to "operator T()
const".
The operator->() overload is there to allow declarations like this:
safe_type<Foo*> m_foo;
To be used in place of
Foo* m_foo;
Although it makes sense to zero-initialize a pointer that is a member
of a class, it is usually not a good idea to copy the pointer along
with the rest of the class's data members whenever the class object is
copied. (The reason is of course that with several objects now holding
the same pointer - deciding who deletes the pointer can be quite
complicated and error prone.)
Since a "smart pointer" can handle both zero-initialization and ref-
counted copying of a pointer data member, I would recommend using a
smart pointer (such as boost::shared_ptr or std::tr1::shared_ptr)
instead of safe_type to manage a pointer data member.
Greg
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