On Sep 21, 2010, at 4:13 PM, Quincey Morris wrote:
> On Sep 21, 2010, at 15:37, Sean McBride wrote:
>
>> If I have a plain C struct that contains some Obj-C object pointers like:
>>
>> struct {
>> int boring;
>> NSString* string;
>> } MyStruct
>>
>> What must I do to be safe in GC?
>>
>> a) I know I must allocate my structs using NSAllocateCollectable and
>> NSScannedOption.
>> b) I'm pretty sure I don't need a '__strong' in my struct declaration.
>> (doc say "__strong is implicitly part of any declaration of an Objective-
>> C object reference type.")
>> c) I'm pretty sure if I use a pointer to this struct as an ivar, I must
>> tag it with __strong.
>
> At risk of getting myself into trouble, I'd say correct, correct and correct.
>
>> d) I'm not sure about passing pointers to this struct around. Need I
>> tag all parameters and return values as __strong too? ex:
>>
>> void DoThing (__strong MyStruct* param) { ... }
>
> At ditto risk, I'd say no to '__strong'. Variable 'param' is a stack variable
> is therefore a *root* reference, and as such the concept of strong or weak
> doesn't apply. (That is, AFAIK, applying '__strong' or '__weak' to a stack
> variable *never* has any effect on its behavior in any way.)
Correct. As roots, the stack and registers (i.e. all ways that a parameter
could be passed) are *always* effectively strong.
--
Clark S. Cox III
[email protected]
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