I need to get a pointer to a virtual method, which is in turn a
function pointer, being set by virtual method binding.
Can anyone, please, tell me how to get it? Taking the delegate of the
method won't do, because I need it to behave exactly as a virtual
method call, except I pass the "this" explic
On 03-05-2012 20:46, Gor Gyolchanyan wrote:
I need to get a pointer to a virtual method, which is in turn a
function pointer, being set by virtual method binding.
Can anyone, please, tell me how to get it? Taking the delegate of the
method won't do, because I need it to behave exactly as a virtua
class B: A
{
void foo()
{
writeln("B.foo called");
}
}
void main()
{
auto a = new A();
auto fn = &a.foo;
auto ptr = fn.funcptr;
auto b = new B();
(cast(void function(A))ptr)(b);
}
will this work?
On Thu, May 3, 2012 at 10:54 PM, Alex Rønne Petersen
wrote:
> On
On Thursday, 3 May 2012 at 18:47:11 UTC, Gor Gyolchanyan wrote:
I need to get a pointer to a virtual method, which is in turn a
function pointer, being set by virtual method binding.
Can anyone, please, tell me how to get it? Taking the delegate
of the
method won't do, because I need it to behav
On 05/03/2012 09:01 PM, Gor Gyolchanyan wrote:
class B: A
{
void foo()
{
writeln("B.foo called");
}
}
void main()
{
auto a = new A();
auto fn =&a.foo;
auto ptr = fn.funcptr;
auto b = new B();
(cast(void function(A))ptr)(b);
}
will this work?
It sho
No, because I'm not supposed to get delegates in the first place. What
I want is to have a pointer to a pointer to a function, so I can make
a true virtual call.
On Thu, May 3, 2012 at 11:09 PM, Mehrdad wrote:
> On Thursday, 3 May 2012 at 18:47:11 UTC, Gor Gyolchanyan wrote:
>>
>> I need to get a
So, you're saying, that the foo function actually takes the *this,
which we ass manually, extracts the real foo method and calls it?
AFAIK, that shouldn't be the case. The delegate extracts the A's foo
and call to the delegate should be a direct call to A.foo, not a
virtual call.
On Thu, May 3, 20
On 05/03/2012 09:18 PM, Gor Gyolchanyan wrote:
So, you're saying, that the foo function actually takes the *this,
which we ass manually, extracts the real foo method and calls it?
AFAIK, that shouldn't be the case. The delegate extracts the A's foo
and call to the delegate should be a direct call
On Thu, 03 May 2012 14:46:58 -0400, Gor Gyolchanyan
wrote:
I need to get a pointer to a virtual method, which is in turn a
function pointer, being set by virtual method binding.
Not exactly. There is a workaround:
http://www.drdobbs.com/blogs/cpp/231600610
-Steve
That workaround is pretty obvious, but I can't afford to make an extra
call every time. This event system is supposed to be ultra-fast. Isn't
there a way to get to the vtable etry itself?
On Thu, May 3, 2012 at 11:26 PM, Steven Schveighoffer
wrote:
> On Thu, 03 May 2012 14:46:58 -0400, Gor Gyolch
No, I intend to call these methods very frequently and I can't afford
any performance loss.
What I expect to have is something like a virtual table entry. I tied
looking at the virtual tables and searching for the method delegate's
.funcptr in the vtable, but didn't find it.
Having that vtable en
Le 03/05/2012 22:22, Gor Gyolchanyan a écrit :
That workaround is pretty obvious, but I can't afford to make an extra
call every time. This event system is supposed to be ultra-fast. Isn't
there a way to get to the vtable etry itself?
Well :
1/ Such a trivial thing is surely inlined by any comp
Good point. That raises the question: How should I make the fastest
possible dynamic dispatch of this kind?
On Fri, May 4, 2012 at 12:57 AM, deadalnix wrote:
> Le 03/05/2012 22:22, Gor Gyolchanyan a écrit :
>
>> That workaround is pretty obvious, but I can't afford to make an extra
>> call every
On Thu, 03 May 2012 16:22:56 -0400, Gor Gyolchanyan
wrote:
That workaround is pretty obvious, but I can't afford to make an extra
call every time. This event system is supposed to be ultra-fast. Isn't
there a way to get to the vtable etry itself?
Well, you can use the ABI to determine the _
On Thu, 03 May 2012 16:57:01 -0400, deadalnix wrote:
Le 03/05/2012 22:22, Gor Gyolchanyan a écrit :
That workaround is pretty obvious, but I can't afford to make an extra
call every time. This event system is supposed to be ultra-fast. Isn't
there a way to get to the vtable etry itself?
1/ S
Basically I want to make a dynamic typing subsystem in D. I want to
take a given object of a static type, construct a dynamic interface
for it and later use that interface to event handling.
To construct a dynamic interface, I need to extract the virtual
methods without resolving them prematurely.
class Foo
{
void test() { }
}
void main(string[] args)
{
auto f = new Foo();
stderr.writeln(f.__vptr[6]);
auto del = (&f.test);
stderr.writeln(del.funcptr);
}
Cool! Thanks!
So all I need to do is remember the indices of functions in the vtable
and extract them manually every time like this, right?
On Fri, May 4, 2012 at 5:31 AM, Mehrdad wrote:
> class Foo
> {
> void test() { }
> }
>
> void main(string[] args)
> {
> auto f = new Foo();
>
On 2012-05-03 20:46, Gor Gyolchanyan wrote:
I need to get a pointer to a virtual method, which is in turn a
function pointer, being set by virtual method binding.
Can anyone, please, tell me how to get it? Taking the delegate of the
method won't do, because I need it to behave exactly as a virtua
Thanks, I'll look into it.
On Fri, May 4, 2012 at 11:25 AM, Jacob Carlborg wrote:
> On 2012-05-03 20:46, Gor Gyolchanyan wrote:
>>
>> I need to get a pointer to a virtual method, which is in turn a
>> function pointer, being set by virtual method binding.
>> Can anyone, please, tell me how to get
On Thursday, 3 May 2012 at 18:47:11 UTC, Gor Gyolchanyan wrote:
I need to get a pointer to a virtual method, which is in turn a
function pointer, being set by virtual method binding.
Can anyone, please, tell me how to get it? Taking the delegate
of the
method won't do, because I need it to behav
Does this have an overhead over calling virtual method directly?
On Fri, May 4, 2012 at 1:30 PM, jerro wrote:
> On Thursday, 3 May 2012 at 18:47:11 UTC, Gor Gyolchanyan wrote:
>>
>> I need to get a pointer to a virtual method, which is in turn a
>> function pointer, being set by virtual method bi
On Friday, 4 May 2012 at 09:51:51 UTC, Gor Gyolchanyan wrote:
Does this have an overhead over calling virtual method directly?
If you call the function directly, it probably gets inlined.
If you call it through a function pointer, it does have some
overhead over calling the virtual method direc
So, the only overhead in making a virtual call this way over calling
the method directly is exactly 1 extra function call?
On Fri, May 4, 2012 at 2:02 PM, jerro wrote:
> On Friday, 4 May 2012 at 09:51:51 UTC, Gor Gyolchanyan wrote:
>>
>> Does this have an overhead over calling virtual method dire
On Friday, 4 May 2012 at 10:05:54 UTC, Gor Gyolchanyan wrote:
So, the only overhead in making a virtual call this way over
calling
the method directly is exactly 1 extra function call?
I guess so. You are calling a function that does a virtual call
and doesn't do anything else, so what other
Great! Thanks!
After I'm done with this, I'll propose adding it to Phobos.
A genuine dynamic dispatch mechanism would be very useful.
On Fri, May 4, 2012 at 6:04 PM, jerro wrote:
> On Friday, 4 May 2012 at 10:05:54 UTC, Gor Gyolchanyan wrote:
>>
>> So, the only overhead in making a virtual call t
Did you see my solution? I think it's what you're looking for...
On Friday, 4 May 2012 at 10:05:54 UTC, Gor Gyolchanyan wrote:
So, the only overhead in making a virtual call this way over
calling
the method directly is exactly 1 extra function call?
On Fri, May 4, 2012 at 2:02 PM, jerro wrote
Yes! Your solution looks exactly like what I wanted. The reason why I
considered additional alternatives is because your solutions looks
very fast (YES!!!), but not very portable and safe, so after testing,
if it turns out to be inconsistent, I'll have to use something else.
On Fri, May 4, 2012 at
Ah okay. Yeah it's not 'safe' at all... but I think the '6' comes
from the number of members that Foo has. If you figure out how
many methods there are in the v-table, then that should get you
the index (though don't quote me on this... you should look at
the compiler source code if you want to
I'm not going to cherry-pick methods in any case. I'll have all
methods analyzed at compile time, by iterating over the overloads of
each method and have them searched in the vtable to get their indices
at launch time. It'll be easy to construct a dynamic virtual method
call.
On Fri, May 4, 2012 a
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