Re: inline virtual functions
On Jul 3, 4:56 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:
siddhu wrote:
Dear experts,
A virtual function has to have an address.
Really? Why?
For the same reason every function has to have an address. You
can take its address with the & operator.
Beyond that, of course, the compiler might want the address for
some internal house keeping. In the case of a virtual function,
this is in fact very likely. (But of course, that's the
compiler's problem, not yours.)
Note that the standard guarantees that all instances of the
address of the function compare equal, even when they are taken
in different compilation units.
So if an inline virtual
function is actually inlined then in that case what does address of
this function signify?
If a function is inlined, the compiler is still free to create a body
of it _if_ it needs to take the address.
How does compiler know at compile time about
the actual object a pointer points to so that it can paste the correct
inline function in the place of function call if the function is
getting inlined?
It doesn't. The whole point of polymorphism is that the type of the
actual object is unknown until the run time.
And of course, just because you say "inline" doesn't mean that
the compiler has to generate the function inline (and vice
versa). In the case of a virtual function called through a
pointer or a reference, there's a very, very good chance that
the compiler won't inline it (although I've heard of some that
do, in some special cases).
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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