On Wed, 10 Apr 2013 11:39:20 +0100, Manu <[email protected]> wrote:
All your examples all hinge on the one case where the optimisation may
possibly be valid, a is _allocated in the same scope_.
Correct, that was the whole point. I am trying to establish where the
"problem" arises, starting from the most basic examples :)
Consider:
The example below is, I presume, supposed to be a function call in user
code where A is defined in a library, correct?
If so, I agree with the issues stated.
If not, if A, and B, and any other classes derived from A are all compiled
at the same time(*) and we're producing an exe then the compiler has all
the information it needs to decide which methods MUST be virtual, and all
others should be non-virtual.
This is the point I was trying to establish with my simpler examples :)
(*) Yes, perhaps you compile a.d then b.d separately - this may result in
the same problem case as a library, or it may not - I don't have the
understanding/data to say one way or the other.
void func(A* a)
{
a.isVirt(); // is it? I guess...
a.notVirt(); // what about this?
}
We don't even know what a B is, or whether it even exists.
Assuming A and B come from a library and are not present in the source we
are compiling with this function, yes.
All we know is that A's methods are virtual by default, and they could be
overridden somewhere else. It's not possible to assume otherwise.
If we're compiling A, and some number of sub-classes of A, and producing
an exe, then from the definition of A, B, and all sub-classes we know
which methods have been overridden, those are virtual, all others are
non-virtual.
R
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