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digitalmars.D.learn - this pointer

reply Zarathustra <adam.chrapkowski gmail.com> writes:
Why value of pointer to this is different in global function, member function
and constructor?
//---------------------------------------------------------------------------------------------------
module test;
class Foo{
  this(){
    writefln("ctor 0x%08X", cast(dword)&this);
  }

  void func(){
    writefln("func 0x%08X", cast(dword)&this);
  }
}
import std.stdio;

void main(){
    Foo foo = new Foo;
    writefln("main 0x%08X", cast(dword)&foo);
    foo.func();    
}
//---------------------------------------------------------------------------------------------------
sample output:
ctor 0x0012FEC8
main 0x0012FEE8
func 0x0012FEB8
Oct 21 2009
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 21 Oct 2009 16:53:20 -0400, Zarathustra  
<adam.chrapkowski gmail.com> wrote:


 Why value of pointer to this is different in global function, member  
 function and constructor?
 //---------------------------------------------------------------------------------------------------
 module test;
 class Foo{
   this(){
     writefln("ctor 0x%08X", cast(dword)&this);
   }

   void func(){
     writefln("func 0x%08X", cast(dword)&this);
   }
 }
 import std.stdio;

 void main(){
     Foo foo = new Foo;
     writefln("main 0x%08X", cast(dword)&foo);
     foo.func();
 }
 //---------------------------------------------------------------------------------------------------
 sample output:
 ctor 0x0012FEC8
 main 0x0012FEE8
 func 0x0012FEB8



&this is the address of the pointer itself (local function argument on the  
stack), not what it points to.  you want cast(void *)this.

-Steve
Oct 21 2009
parent reply Zarathustra <adam.chrapkowski gmail.com> writes:
Steven Schveighoffer Wrote:


 On Wed, 21 Oct 2009 16:53:20 -0400, Zarathustra  
 <adam.chrapkowski gmail.com> wrote:
 

 Why value of pointer to this is different in global function, member  
 function and constructor?
 //---------------------------------------------------------------------------------------------------
 module test;
 class Foo{
   this(){
     writefln("ctor 0x%08X", cast(dword)&this);
   }

   void func(){
     writefln("func 0x%08X", cast(dword)&this);
   }
 }
 import std.stdio;

 void main(){
     Foo foo = new Foo;
     writefln("main 0x%08X", cast(dword)&foo);
     foo.func();
 }
 //---------------------------------------------------------------------------------------------------
 sample output:
 ctor 0x0012FEC8
 main 0x0012FEE8
 func 0x0012FEB8



 &this is the address of the pointer itself (local function argument on the  
 stack), not what it points to.  you want cast(void *)this.
 
 -Steve



Thank's a lot. God blesses C++ for the '->' operator ;)
Oct 21 2009
parent BCS <none anon.com> writes:
Hello Zarathustra,


 Thank's a lot. God blesses C++ for the '->' operator ;)



God curse C++ for the '->' operator. 

And I'm not making a Joke, I hate that thing! 

It makes a distinction between value and reference semantics where they don't 
matter (lookup) and does nothing for the cases (assignment, arg passing) 
where it does.
Oct 21 2009