Pointer to int

Pointer to int

[Ronaldo Zacarias Afonso]

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  Hello everybody, 

  I'm iniciating in the C programming language and there are some things 
that I realy need to understand, so the question is: 

  In the code: 

  int i; 
  struct some_struct *ptr; 

  ptr = &some_other_struct; 

  i = (int) ptr; 


  1) Is the last sentence a valid one? 
  2) If it is, what is realy happening? 

note - It seems very stranger to me. A struct pointer being "transformed" 
into a int variable. 

  Thanks. 


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Re: Pointer to int

[Luiz Fernando N. Capitulino]

 Hi Ronaldo,

Em Wed, 21 Jul 2004 18:11:29 -0300
Ronaldo Zacarias Afonso <r_zaca@ig.com.br> screveu:

|   I'm iniciating in the C programming language and there are some things 
| that I realy need to understand, so the question is: 
| 
|   In the code: 
| 
|   int i; 
|   struct some_struct *ptr; 
| 
|   ptr = &some_other_struct; 
| 
|   i = (int) ptr; 
| 
| 
|   1) Is the last sentence a valid one? 

 Yes, but depending on the architecture the int variable will not be enough.

|   2) If it is, what is realy happening? 
| 
| note - It seems very stranger to me. A struct pointer being "transformed" 
| into a int variable. 

 Variables address are also numbers, so you can handle it with int variables.

 The two most important questions here are: 1) you need to _know_ exactly what
you are doing, and 2) the variable size.

 For i386 architecture, you will need a 32-bit variable to store an address, so
for you example "unsigned int" is what we want (assuming you want all the address,
maybe you want a half of it, or something like that).

 And do a +1 in a pointer is not the something to do a +1 in the `i' above.

-- 
Luiz Fernando

Re: Pointer to int

[canbaby]

Ronaldo Zacarias Afonso wrote:

>  Hello everybody, 
>
>  I'm iniciating in the C programming language and there are some things 
>that I realy need to understand, so the question is: 
>
>  In the code: 
>
>  int i; 
>  struct some_struct *ptr; 
>
>  ptr = &some_other_struct; 
>
>  i = (int) ptr; 
>
>
>  1) Is the last sentence a valid one? 
>  2) If it is, what is realy happening? 
>
>note - It seems very stranger to me. A struct pointer being "transformed" 
>into a int variable. 
>
>  Thanks. 
>
>
>_________________________________________________________________________________
>Quer mais velocidade?
>Só com o acesso Aditivado iG, a velocidade que você quer na hora que você precisa.
>Clique aqui: http://www.acessoaditivado.ig.com.br
>
>  
>
yes,it's a validate one.
now the var i have the the some_other_struct address value,you could 
reconstruct the struct like this:
struct some_struct *newstruct = (struct some_struct *)i;
then freely use the newstruct.
-
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