Re: NSArray's objectAtIndex compiles to objectAtIndexedSubscript?
Re: NSArray's objectAtIndex compiles to objectAtIndexedSubscript?
- Subject: Re: NSArray's objectAtIndex compiles to objectAtIndexedSubscript?
- From: Kyle Sluder <email@hidden>
- Date: Fri, 07 Mar 2014 08:50:33 -0800
On Mar 7, 2014, at 4:54 AM, Bill Cheeseman <email@hidden> wrote:
>
> My code calls -[NSArray objectAtIndex:]. I compile it with Xcode 5.0.2 on OS X 10.9.x Mavericks in a project with the target's Base SDK set to 10.9 and the OS X Deployment Target set to OS X 10.7. It works fine when I run it on OS X 10.9 or OS X 10.8.
>
> However, when I run it on Mac OS X 10.7 Lion, I get a runtime error claiming it encountered an invalid argument, namely, the unrecognized selector -objectAtIndexedSubscript:. The NSArray Class Reference notes that -objectAtIndexedSubscript: is available only in OS X 10.8 and later, and that it is "identical to objectAtIndex:". Of course, -objectAtIndex: still exists in the 10.9 API, and it is not marked as deprecated.
>
> It appears, therefore, that the compiler generated a call to -objectAtIndexedSubscript: even though my source specifies -objectAtIndex: and a deployment version of 10.7.
>
> Has anyone else encountered this? -- I don't find anything in my searches. It seems like a serious bug that would have cropped up for practically everybody.
-objectAtIndexedSubscript: is what the compiler generates when it sees square-bracket indexing syntax applied to an NSArray:
NSArray *a = …;
foo(a[0]); // generates call to -objectAtIndexedSubscript:
It’s unfortunate that the compiler doesn’t catch that you’re targeting 10.7, where this method does not exist, and prevent such syntax.
>
> My actual code is this:
>
> NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSSystemDomainMask, YES) objectAtIndex:0];
This doesn’t look like the code that’s breaking. Is that really what’s on the stack when you crash? If so, that’s a pretty serious compiler bug.
>
> I could try casting the result of NSSearchPathForDirectoriesInDomains() to type NSArray* or break this statement into two parts with an intermediate NSArray local variable, but I can't see why that would make any difference.
>
> Is there any way to work around this?
>
> I notice that the 10.7 Lion SDK is not part of the Xcode 5 installation. Do I have to add the 10.7 Lion SDK? -- and how would I go about doing that?
The Lion SDK is not supported with Xcode 5.
--Kyle Sluder
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