I have an external variable declared like this:

struct
ControlID
{
	uint			signature;
	int				id;
};
extern extern (C) const HIViewID kHIViewWindowContentID;

But when I am able to write code like this without complaint from the compiler (GDC 0.21/DMD 1.00):

kHIViewWindowContentID.signature = 123;

I'd like to prevent that. Is such a thing possible?

TIA,
Rick

Rick Mann wrote:
> I have an external variable declared like this:
> 
> struct
> ControlID
> {
> 	uint			signature;
> 	int				id;
> };
> extern extern (C) const HIViewID kHIViewWindowContentID;
> 
> But when I am able to write code like this without complaint from the compiler (GDC 0.21/DMD 1.00):
> 
> kHIViewWindowContentID.signature = 123;
> 
> I'd like to prevent that. Is such a thing possible?
> 

Why doesn't private protection work on structs? I tested it with DMD 1.003 and was surprised by the result.

struct ControlID {
  private uint signature_;
  private int id_;
	
  uint signature() {
    return signature_;
  }
}

void main() {
  ControlID id;
  id.signature = 123;  // Compiler error
  uint i = id.signature;

  id.signature_ = 123;  // Doesn't fail. Should it?
}

Bradley Smith wrote:
> Rick Mann wrote:
>> I have an external variable declared like this:
>>
>> struct
>> ControlID
>> {
>>     uint            signature;
>>     int                id;
>> };
>> extern extern (C) const HIViewID kHIViewWindowContentID;
>>
>> But when I am able to write code like this without complaint from the compiler (GDC 0.21/DMD 1.00):
>>
>> kHIViewWindowContentID.signature = 123;
>>
>> I'd like to prevent that. Is such a thing possible?
>>
> 
> Why doesn't private protection work on structs? I tested it with DMD 1.003 and was surprised by the result.
> 
> struct ControlID {
>   private uint signature_;
>   private int id_;
>       uint signature() {
>     return signature_;
>   }
> }
> 
> void main() {
>   ControlID id;
>   id.signature = 123;  // Compiler error
>   uint i = id.signature;
> 
>   id.signature_ = 123;  // Doesn't fail. Should it?
> }

Isn't that because protection attributes are applied at the module level, not class/struct level?

--bb

Bill Baxter wrote:
> Bradley Smith wrote:
>>
>> Why doesn't private protection work on structs? I tested it with DMD 1.003 and was surprised by the result.
>>
>> struct ControlID {
>>   private uint signature_;
>>   private int id_;
>>       uint signature() {
>>     return signature_;
>>   }
>> }
>>
>> void main() {
>>   ControlID id;
>>   id.signature = 123;  // Compiler error
>>   uint i = id.signature;
>>
>>   id.signature_ = 123;  // Doesn't fail. Should it?
>> }
> 
> Isn't that because protection attributes are applied at the module level, not class/struct level?
> 
> --bb

That's exactly it. Thanks. I forgot that fact. If I move main() into another module, I get the error "struct privateStruct.ControlID member signature_ is not accessible".

Thanks,
  Bradley

On Wed, 31 Jan 2007 15:33:24 -0800, Bradley Smith wrote:

> Why doesn't private protection work on structs?

The 'private' protection means that such items cannot be accessed by things in other *modules* and not just other classes/structs. In other words, any thing in a module has access to everything in the same module.

However, a long-existing bug means that you can still subvert this protection by simply referencing a private item in a different module by using it's fully qualified name.

 -------
 module foo;
 private int A;

 -------
 module bar;
 import foo;
 . . .
    foo.A = 42;  // Allowed but should not be.
    A = 42;      // Correctly disallowed.

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
1/02/2007 11:17:14 AM