[swift-users] C Pointers and Memory

[James Campbell]

No I haven't thats a big help thank you !

*___________________________________*

*James⎥Head of Trolls*

*james at supmenow.com <james at supmenow.com>⎥supmenow.com <http://supmenow.com>*

*Sup*

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On 29 July 2016 at 10:40, Zhao Xin <owenzx at gmail.com> wrote:

> Have you read
> https://developer.apple.com/library/tvos/documentation/Swift/Conceptual/BuildingCocoaApps/InteractingWithCAPIs.html#//apple_ref/doc/uid/TP40014216-CH8-ID17
>  ?
>
> Zhaoxin
>
> On Fri, Jul 29, 2016 at 4:55 PM, James Campbell via swift-users <
> swift-users at swift.org> wrote:
>
>> ​Do you know of any resources to brush up on the pointer aspect of swift
>> ? ​
>>
>> *___________________________________*
>>
>> *James⎥Head of Trolls*
>>
>> *james at supmenow.com <james at supmenow.com>⎥supmenow.com
>> <http://supmenow.com>*
>>
>> *Sup*
>>
>> *Runway East *
>>
>> *10 Finsbury Square*
>>
>> *London*
>>
>> * EC2A 1AF *
>>
>> On 29 July 2016 at 09:10, Dmitri Gribenko <gribozavr at gmail.com> wrote:
>>
>>> On Fri, Jul 29, 2016 at 12:55 AM, James Campbell <james at supmenow.com>
>>> wrote:
>>> > So this:
>>> >
>>> > if let data = someArrayGeneratingFunction() {
>>> >   cFunction(UnsafeMutablePointer(data))
>>> > }
>>> >
>>> > Has issues with the array passed to c getting corrupted, but this
>>> doesn't:
>>> >
>>> > let data = someArrayGeneratingFunction()
>>> >
>>> > if let data = data {
>>> >   cFunction(UnsafeMutablePointer(data))
>>> > }
>>>
>>> Neither piece of code is guaranteed to work.  (You are just getting
>>> lucky that the second one happens to work.)  Array-to-pointer
>>> conversion only extends the lifetime of the array until the immediate
>>> function call returns.  So after UnsafeMutablePointer(data) returns,
>>> the array can be freed.
>>>
>>> Use someArrayGeneratingFunction.withUnsafeMutableBuffer { ... } instead.
>>>
>>> Dmitri
>>>
>>> --
>>> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
>>> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com>*/
>>>
>>
>>
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>
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