Re: using a class inside a class.
On Apr 29, 10:57 am, Ian Collins <ian-n...@hotmail.com> wrote:
James Kanze wrote:
On Apr 28, 8:33 pm, "Jim Langston" <tazmas...@rocketmail.com> wrote:
All I can tell you is I've done this exact same thing in the past
successfully in both Microsoft Visual C++ .net 2003 and DevC++. Here i=
s
something that compiles sucessfully in Microsoft Visual C++ .net 2003:
#include <list>
class CFoo
{
private:
std::list<CFoo> m_children;
};
int main()
{
CFoo Foo;
}
No warnings, no errors.
That's what's so nice about undefined behavior. The fact that
it works doesn't prove anything.
I don't know why your version of gcc is complaining, I don't
think it should, AFAIK this is perfectly legal, although I
haven't read the standard on it.
=A717.4.3.6/2:
In particular, the effects are undefined in the
following cases:
[...]
-- if an incomplete type (3.9) is used as a template
argument when instantiating a template component.
A class is only a complete type after the closing braces, so
your code has undefined behavior. (The standard could have
allowed incomplete types for certain specific cases, but it
didn't.)
But isn't the template component being instantiated in main
after the class is complete?
The class itself will be instantiated anytime it is used in a
context where a complete type is required. (How could it be
otherwise?) Class members (functions, static data members) will
be instantiated when (and only when) they are used. Since only
complete types can be used as member variables, the class itself
must be instantiated in CFoo. (Note that declaring the type as
"std::list< CFoo >* m_children" should work.)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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