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POBoxing the same enum member produces a larger integer when it's passed to a method
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  1. POBoxing the same enum member produces a larger integer when it's passed to a method
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    copied!<p>I'm using Clang's primitive-boxing feature to pack an enumeration member into <code>NSNumber</code></p> <p>The <a href="http://clang.llvm.org/docs/ObjectiveCLiterals.html#objc_boxed_expressions" rel="nofollow">Boxed Enums section</a> of the Clang doc about this says that the compiler boxes enumeration members into integers, unless the type is specified.</p> <p>Funnily enough, I get different sizes of integers depending on the way I'm passing the enumeration member to the method. I've been able to isolate the case down to the following code</p> <pre><code>typedef enum _MyEnum { MyEnumMember1 = 1000 } MyEnum; - (void)testEnumerationBoxing { NSNumber *numberA = [self testA]; NSNumber *numberB = [self testB:MyEnumMember1]; CFNumberType numberTypeA = CFNumberGetType((__bridge CFNumberRef) numberA); CFNumberType numberTypeB = CFNumberGetType((__bridge CFNumberRef) numberB); NSLog(@"CF Number type for A: %lu; B: %lu", numberTypeA, numberTypeB); } - (NSNumber *)testA { return @(MyEnumMember1); } - (NSNumber *)testB:(MyEnum)enumMember { return @(enumMember); } </code></pre> <p>The console output is </p> <blockquote> <p>CF Number type for A: 3; B: 4 </p> </blockquote> <p>(the first one is <code>kCFNumberSInt32Type</code>, the second one is <code>kCFNumberSInt64Type</code>)</p> <p>If I change declaration to <code>typedef enum _MyEnum : int</code> I see the same result for both: <code>kCFNumberSInt32Type</code>.</p> <p>Why does the size of the integer differ between the two methods of boxing?</p>
 

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