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Re: some unsigned/NSInteger to NSUInteger changes in -gui

by SebastianR :: Rate this Message:

On Tuesday, April 10, 2012 19:24 CEST, David Chisnall <theraven@...> wrote:

> On 10 Apr 2012, at 18:18, Sebastian Reitenbach wrote:
>
> > + {
> > + int tmp = (int)_selected_item;
> > + [aDecoder decodeValueOfObjCType: @encode(int) at: &_selected_item];
> > + _selected = [_items objectAtIndex: tmp];
> > + }
>
> No, this is still wrong, and I'm not really sure what it's trying to do...
>
> Let's say you're on some big-endian LP64 system. NSInteger will be a 64-bit integer while int will be a 32-bit integer. You pass a pointer to the NSInteger to aDecoder, and tell it that it's a pointer to an int. It will then cast this pointer and will write a 32-bit value into the first 32 bits of the ivar. Unfortunately, because this is a big endian system, you've now set the value to something about four billion times as big as it should be...
>
> As I said in my last email, the correct form is:
>
> int tmp;
> [aDecoder decodeValueOfObjCType: @encode(int) at: &tmp];
> _selected_item = tmp;
>
> This creates an int on the stack and passes a pointer to it to aDecoder, which then loads an int-sized value and stores it in the int. You then assign this value to the ivar. The implicit cast (you can make it explicit if you prefer) will extend this to the correct size.

Thanks for your patience. Now I got it, the decoder already has the value, and just puts it in, where the pointer points it to. But I still think I need to assign
_selected = [_items objectAtIndex: tmp];

so that it will be right.

Sebastian

Index: NSTabView.m
===================================================================
--- NSTabView.m (revision 35052)
+++ NSTabView.m (working copy)
@@ -52,7 +52,7 @@
{
if (self == [NSTabView class])
{
- [self setVersion: 2];
+ [self setVersion: 3];

[self exposeBinding: NSSelectedIndexBinding];
[self exposeBinding: NSFontBinding];
@@ -550,7 +550,7 @@
[aCoder encodeValueOfObjCType: @encode(BOOL) at: &_draws_background];
[aCoder encodeValueOfObjCType: @encode(BOOL) at: &_truncated_label];
[aCoder encodeConditionalObject: _delegate];
- [aCoder encodeValueOfObjCType: "I" at: &_selected_item];
+ [aCoder encodeValueOfObjCType: @encode(NSUInteger) at: &_selected_item];
}
}

@@ -631,8 +631,17 @@
[aDecoder decodeValueOfObjCType: @encode(BOOL) at: &_draws_background];
[aDecoder decodeValueOfObjCType: @encode(BOOL) at: &_truncated_label];
_delegate = [aDecoder decodeObject];
- [aDecoder decodeValueOfObjCType: "I" at: &_selected_item];
- _selected = [_items objectAtIndex: _selected_item];
+ if (version < 3)
+ {
+ int tmp;
+ [aDecoder decodeValueOfObjCType: @encode(int) at: &tmp];
+ _selected = [_items objectAtIndex: tmp];
+ }
+ else
+ }
+ [aDecoder decodeValueOfObjCType: @encode(NSUInteger) at: &_selected_item];
+ _selected = [_items objectAtIndex: _selected_item];
+ }
}
return self;
}

>
> David
>
> -- Sent from my Cray X1

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