Autogenerated ivars not retained by ARC

Originator:hamish
Number:rdar://9842232 Date Originated:26-Jul-2011 06:45 PM
Status:Closed (Behaves Correctly) Resolved:
Product:iPhone SDK [sic] Product Version:5.0 beta 4
Classification:Serious Bug Reproducible:Always
 
Summary:
EXC_BAD_ACCESS arises when using autogenerated ivars (@synthesize prop = myProp with no declaration of myProp).

Steps to Reproduce:
See https://gist.github.com/1107320

Expected Results:
The same behaviour whether or not the ivar declarations are commented out.

Actual Results:
Crash when the ivar declarations are commented out.

Regression:
Unknown.

Notes:
P.S. Please rename "iPhone SDK" and "iPad SDK" under "Product" in the bug reporter to "iOS". Thanks!

Comments

Marked as Fixed (Behaves Correctly) with the explanation:

"For historical reasons, properties that aren't explicitly strong or weak are implicitly "assign", which for Objective-C pointers means unsafe_unretained. This is "correct" but very unsafe, as you've found, and so ARC will now output an error on this code. Instead, you must explicitly say that a property of Objective-C pointer type is strong, weak, or unsafe_unretained before you synthesize it, like so: @property(strong, nonatomic, readonly) UILabel *textLabel; Furthermore, if the synthesized ivar already exists, ARC will verify that it has matching semantics; if the synthesized ivar does not already exist, it will be created with matching semantics."

By hamish at Nov. 3, 2011, 1:59 p.m. (reply...)

If you set a storage type in the @property it'll work, otherwise it defaults to unsafe_unretained.

(Not breaking NDA, this is at http://clang.llvm.org/docs/AutomaticReferenceCounting.html)

By jediknil at July 26, 2011, 9:19 p.m. (reply...)

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