<div dir="ltr"><div>Does addressof count as legally observing it?<br><br><span style="font-family:monospace,monospace"> var buffers:(GL.UInt, </span><span style="font-family:monospace,monospace"><span style="font-family:monospace,monospace">GL.UInt)</span> = (0, 0)<br> glGenBuffers(n: 2, buffers: &</span><span style="font-family:monospace,monospace"><span style="font-family:monospace,monospace">buffers.0</span>)</span><br><br></div>Also, I assume Swift performs a swizzle if the tuple is defined in a separate module from where the pointer to it is constructed?<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jul 20, 2017 at 4:59 AM, Johannes Weiß <span dir="ltr"><<a href="mailto:johannesweiss@apple.com" target="_blank">johannesweiss@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">When you can (legally) observe it, tuples in Swift have guaranteed standard C-style layout.<br>
<br>
John McCall confirms this here: <a href="https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20170424/004481.html" rel="noreferrer" target="_blank">https://lists.swift.org/<wbr>pipermail/swift-dev/Week-of-<wbr>Mon-20170424/004481.html</a><br>
<div><div class="h5"><br>
> On 20 Jul 2017, at 4:33 am, Taylor Swift via swift-users <<a href="mailto:swift-users@swift.org">swift-users@swift.org</a>> wrote:<br>
><br>
> Many APIs like OpenGL take arrays where the atomic unit is multiple elements long. For example, a buffer of coordinates laid out like<br>
><br>
> :[Float] = [ x1, y1, z1, x2, y2, z2, ... , xn, yn, zn ]<br>
><br>
> I want to be able to define in Swift (i.e., without creating and importing a Objective C module) a struct that preserves the layout, so that I can do withMemoryRebound(to:capacity:<wbr>_) or something similar and treat the buffer as<br>
><br>
> struct Point<br>
> {<br>
> let x:Float,<br>
> y:Float,<br>
> z:Float<br>
> }<br>
><br>
> :[Point] = [ point1, point2, ... , pointn ]<br>
><br>
> The memory layout of the struct isn’t guaranteed, but will the layout be guaranteed to be in declaration order if I use a tuple inside the struct instead?<br>
><br>
> struct Point<br>
> {<br>
> let _point:(x:Float, y:Float, z:Float)<br>
><br>
> var x:Float<br>
> {<br>
> return self._point.x<br>
> }<br>
><br>
> var y:Float<br>
> {<br>
> return self._point.y<br>
> }<br>
><br>
> var z:Float<br>
> {<br>
> return self._point.z<br>
> }<br>
> }<br>
><br>
> This is an ugly workaround, but I can’t really think of any alternatives that don’t involve “import something from Objective C”. I am aware that the implementation of structs currently lays them out in declaration order, but I’m looking for something that’s actually defined in the language.<br>
><br>
><br>
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<br>
</blockquote></div><br></div>