<div dir="ltr">I'd think the hypothetical way in Swift to write to configuration registers would be to create an UnsafeMutablePointer<Int64> (or some other raw integer type) from a raw memory address, and then get/set the contents using the 'memory' property. Not sure if the compiler is "smart" enough to optimize out memory accesses made using that mechanism, although I would assume no.<div><br></div><div>Austin<br><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 7, 2016 at 3:52 AM, Romain Goyet via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Hi everyone,</div><div><br></div><div>In the <a href="https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/" target="_blank">introduction to Swift</a>, it is presented as an "industrial-quality systems programming language".</div><div>According to <a href="https://en.wikipedia.org/wiki/System_programming_language" target="_blank">Wikipedia</a>, this means that I could expect to be able to write device drivers or operating systems in Swift.</div><div><br></div><div>However it seems like this claim is only partially true, since several important low-level features seem to be completely missing:</div><div><br></div><div>- Is it possible to generate <a href="http://llvm.org/docs/LangRef.html#volatile-memory-accesses" target="_blank">volatile memory accesses</a> in Swift? Writing device drivers is virtually impossible without a way to guarantee certain memory operations are actually made (and not optimized-out). </div><div><br></div><div>- Is it possible to embed raw binary data in Swift? For example, an equivalent of the following C code "const int8_t foo[6] = {0x00,0x11,0x22,0x33,0x44,0x55};"? The simple Swift equivalent, "let foo: [Int8] = [0x0,0x1,0x2,0x3,0x4,0x6];" is obviously wildly different. Being able to embed raw binary data is very important in a low-level environment: for example, you may need to feed specific data to a device for an initialization sequence at a point where you don't have a filesystem available yet.</div><div><br></div><div>There might be other aspects that I'm overlooking right now, but I think that's enough to start a discussion: is Swift really meant to be a systems programming language?</div><div><br></div><div>Thanks,</div><div><br></div><div> - Romain</div></div>
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