[swift-users] Problem calling a C function passing a void** from Swift 3

[Lane Schwartz]

Thank you! This, in conjunction with a later call to bindMemory(to:
capacity:), was exactly what I needed.

On Fri, Sep 16, 2016 at 9:47 AM, Quinn "The Eskimo!" via swift-users <
swift-users at swift.org> wrote:

>
> On 15 Sep 2016, at 22:11, Lane Schwartz via swift-users <
> swift-users at swift.org> wrote:
>
> > Can anyone help me get the equivalent functionality in Swift 3?
>
> I think the main issue here is that, in Swift 3, unsafe pointers, in their
> various flavours, don’t explicitly support nil.  Rather, nil is modelled
> like it is for any other type, via `Optional`.  You can read all about this
> change in SE-0055 [1]
>
> So, if you have an C API like this:
>
> extern int HackAlloc(void ** bufPtrPtr, size_t bufSize);
> extern void HackFree(void * bufPtr);
>
> you can call it like this:
>
> var buf: UnsafeMutableRawPointer? = nil
> let result = HackAlloc(&buf, 1024)
> if result == 0 {
>     HackFree(buf)
> }
>
> This is very similar to what you currently have except that `buf` is
> explicitly made optional.
>
> The other difference is that `buf` is a ‘raw’ pointer, which means you
> have to understand Swift 3’s type aliasing rules.  You can read about the
> details in SE-0107 [2] bug a good place to start is the “UnsafeRawPointer
> Migration” section of the Swift 3 migration guide.
>
> <https://swift.org/migration-guide/se-0107-migrate.html>
>
> Share and Enjoy
> --
> Quinn "The Eskimo!"                    <http://www.apple.com/developer/>
> Apple Developer Relations, Developer Technical Support, Core OS/Hardware
>
> [1]: <https://github.com/apple/swift-evolution/blob/master/
> proposals/0055-optional-unsafe-pointers.md>
>
> [2]: <https://github.com/apple/swift-evolution/blob/master/proposals/0107-
> unsaferawpointer.md>
>
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