[swift-evolution] Low-level Swift

[Austin Zheng]

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.

Austin

On Thu, Jan 7, 2016 at 3:52 AM, Romain Goyet via swift-evolution <
swift-evolution at swift.org> wrote:

> Hi everyone,
>
> In the introduction to Swift
> <https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/>,
> it is presented as an "industrial-quality systems programming language".
> According to Wikipedia
> <https://en.wikipedia.org/wiki/System_programming_language>, this means
> that I could expect to be able to write device drivers or operating systems
> in Swift.
>
> However it seems like this claim is only partially true, since several
> important low-level features seem to be completely missing:
>
> - Is it possible to generate volatile memory accesses
> <http://llvm.org/docs/LangRef.html#volatile-memory-accesses> in Swift?
> Writing device drivers is virtually impossible without a way to guarantee
> certain memory operations are actually made (and not optimized-out).
>
> - 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.
>
> 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?
>
> Thanks,
>
>  - Romain
>
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>
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