Re: Can an NSArray ever have a count of -1?
Re: Can an NSArray ever have a count of -1?
- Subject: Re: Can an NSArray ever have a count of -1?
- From: Jens Alfke <email@hidden>
- Date: Fri, 19 Feb 2016 13:29:45 -0800
> On Feb 19, 2016, at 1:17 PM, Jim Adams <email@hidden> wrote:
>
> SLogInfo(@"Starting csi %ld count %d", csi, sortedEvents.count);
>
> In the console I see:
> INFO: Starting csi -1 count -1
> The very next line crashes when the sortedEvents are accessed. What could cause the array to have a -1 count?
You’re using the wrong format strings for both of those parameters.
csi is 64-bit so you need %lld. The formatter sees %ld and thinks it’s 32-bit not 64-bit, so it skips the wrong amount of space on the stack when going to the next parameter, which is why you then get a bogus value for the count.
Also, NSArray.count is of type NSUInteger, which is unsigned, and has different sizes on different platforms. The right format specifier is either %lu (in a 32-bit app) or %llu (in 64-bit).
FYI, You must be ignoring compiler warnings, or you've turned off the “type check printf” warning setting. Don’t do that ;) I always strongly recommend turning on “Treat warnings as errors”, which will force you to fix warnings. This is very useful because a number of compiler warnings are actually nasty and hard-to-find errors like the above.
—Jens
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