Re: NSMutableData +dataWithLength: sets errno?
Re: NSMutableData +dataWithLength: sets errno?
- Subject: Re: NSMutableData +dataWithLength: sets errno?
- From: John McCall <email@hidden>
- Date: Tue, 14 Mar 2017 19:08:59 -0400
> On Mar 14, 2017, at 7:00 PM, Carl Hoefs <email@hidden> wrote:
> macOS 10.12.3, Xcode 8.2.1, ObjC
>
> I'm finding the following line to be problematic:
>
> NSMutableData *myData = [NSMutableData dataWithLength:80];
>
> I assume this ends up calling calloc(3) to allocate and zero out the data. But for some reason, it's always setting errno to a seemingly random nonzero value, generally either errno=2 (ENOENT) or errno=22 (EINVAL).
>
> Now that I know it does this, I can make accommodations for it, but is this expected behavior?
I don't know why it's happening here, but unless you're calling a function that specifically documents its errno behavior, you should assume that every call you make might randomly overwrite errno with gibberish.
John.
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