Hi, Ray. Most of the pointer model is covered in the original proposal for the UnsafeRawPointer type, SE-0107 <https://github.com/apple/swift-evolution/blob/master/proposals/0107-unsaferawpointer.md>. That's a good place to find answers to pointer- and memory-related questions in general.
The short forms are "yes, binding memory to types is mostly about communication with the optimizer, but it may also be checkable at run-time some day", and "it's okay to skip 'deinitialize' and use assignment instead of 'initialize' if and only if the element type is trivial <https://github.com/apple/swift-evolution/blob/master/proposals/0107-unsaferawpointer.md#trivial-types>". Additionally, as far as I know, mutation through UnsafeMutableRawBufferPointer doesn't count as binding any type to the memory, but Andy will have to check me on that. Best, Jordan > On Dec 11, 2016, at 14:51, Ray Fix via swift-users <swift-users@swift.org> > wrote: > > Hello, > > So bindMemory is part of the memory model and memory can only bind to one > type at a time to avoid aliasing. But what does binding actually do? Is it > somehow communicating with the optimizer? > > A tangentially related second question, in the following example: > > let count = 3 > let mutablePointer = UnsafeMutablePointer<Int16>.allocate(capacity: count) > defer { > mutablePointer.deallocate(capacity: count) > } > > mutablePointer.initialize(to: 1234, count: count) > defer { > mutablePointer.deinitialize(count: count) // must I do this? > } > > Is it bad form if I don’t deinitialize and go straight to deallocate? I can > see where it is important for ref types (to update ref counts, etc). Is it > one of those things that the optimizer can remove for the case of value types? > > Finally, if I initalize with some other means, such as with a raw buffer > pointer subscript, is there any need to deinitialize? Can such memory be > considered initialized if I bind it with a type? > > // 1 > let pointer = malloc(byteCount) > defer { > free(pointer) > } > > let mutableRawBufferPointer = UnsafeMutableRawBufferPointer(start: pointer, > count: byteCount) > > for index in mutableRawBufferPointer.indices { > mutableRawBufferPointer[index] = 42 + UInt8(index) > } > > Perhaps there is a document or proposal somewhere that talks about these > things. Sorry if I missed it. > > Thanks as always, > Ray > > > _______________________________________________ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users
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