[swift-users] NSMutableData's init?(length length: Int) initializer

Chris Lattner clattner at apple.com
Fri Apr 15 12:34:38 CDT 2016

> On Apr 14, 2016, at 11:22 PM, Dmitri Gribenko <gribozavr at gmail.com> wrote:
> On Thu, Apr 14, 2016 at 11:16 PM, Chris Lattner via swift-users
> <swift-users at swift.org> wrote:
>>> On Apr 14, 2016, at 10:45 AM, soyer via swift-users <swift-users at swift.org> wrote:
>>> Hello Guys, Girls,
>>> Do you know why is the init?(length length: Int) NSMutableData's initializer failable?
>>> The memory allocation can fail, but I think Swift doesn't handle that cases. (it is not a real issue in a modern OS)
>>> The code on github calls a non failable initializer.
>>> https://github.com/apple/swift-corelibs-foundation/blob/master/Foundation/NSData.swift#L904
>> Swift’s policy on memory allocation failure is that fixed-size object allocation is considered to be a runtime failure if it cannot be handled.  OTOH, APIs that can take a variable and arbitrarily large amount to allocate should be failable.  NSData falls into the later category.
> Does this principle apply to Array(repeating:count:)?
> Array.append(contentsOf:)?

As you know well enough, “no”. :-)


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