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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>So basically if I do something like this I should be on the safe side:</p>
<pre><code class="swift">public class Characters {
private let reference: UnsafeMutablePointer<Character>
var characters: [Character] {
var characters = [Character]()
for index in 0..<self.count {
characters.append(self.reference.advancedBy(index).memory)
}
return characters
}
var combined: String { return String(self.characters) }
public let count: Int
public init(value: String) {
let characters = value.characters
self.count = characters.count
self.reference = UnsafeMutablePointer<Character>.alloc(self.count)
self.reference.initializeFrom(characters)
}
deinit {
self.reference.destroy(self.count)
self.reference.dealloc(self.count)
}
}
</code></pre>
<p>Or do I have to fix something? </p>
<p>Here I don’t walk out of the boundary I allocate. </p>
<p>Does the <code>UnsafeMutablePointer</code> reserves me a safe portion of memory (by <em>safe</em> I mean which isn’t used by anyone at the time I will start using it)? </p>
<p>Sure another pointer could be created and hack into my memory but that wasn’t the question. :)</p>
<p>Thanks.</p>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1463821582316001024" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 21. Mai 2016 bei 11:04:10, Dmitri Gribenko (<a href="mailto:gribozavr@gmail.com">gribozavr@gmail.com</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>Hi Adrian,
<br>
<br>On Sat, May 21, 2016 at 1:48 AM, Adrian Zubarev via swift-users
<br><swift-users@swift.org> wrote:
<br>> I played around with UnsafeMutablePointer and realized one behavior:
<br>>
<br>> let pString = UnsafeMutablePointer<String>.alloc(1)
<br>> pString.initialize("test")
<br>> pString.predecessor().memory // will crash ax expected
<br>> pString.predecessor() == pString.advancedBy(-1) // true
<br>> pString.destroy()
<br>> pString.dealloc(1)
<br>>
<br>> where
<br>>
<br>> let iInt = UnsafeMutablePointer<String>.alloc(1)
<br>> iInt.initialize("test")
<br>> iInt.predecessor().memory // will not crash
<br>> iInt.predecessor() == iInt.advancedBy(-1) // true
<br>> iInt.predecessor().memory = 42 // did I just modified some memory I don't
<br>> own?
<br>
<br>Yes, you did.
<br>
<br>In the String case the crash is not guaranteed (it is a segmentation
<br>fault, not a controlled trap). Someone else's valid String can happen
<br>to be located immediately before your memory chunk, and then the code
<br>would "just work", loading that other string.
<br>
<br>Dereferencing (reading or writing into) an out-of-bounds pointer is
<br>undefined behavior in Swift.
<br>
<br>Dmitri
<br>
<br>--
<br>main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
<br>(j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr@gmail.com>*/
<br></div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>