> On Jun 30, 2017, at 7:40 AM, Martin R via swift-users <swift-users@swift.org> > wrote: > > I have a C function > > void myfunc(const void *ptr); > > which is imported to Swift as > > func myfunc(_ ptr: UnsafeRawPointer!) > > This compiles and runs without problems: > > let data = Data(bytes: [1, 2, 3, 4]) > data.withUnsafeBytes { (ptr) in myfunc(ptr) } // (A) > > and the type of `ptr` is inferred as `UnsafePointer<Void>`. But adding an > explicit type > annotation produces a compiler warning:
How do you know the inferred type is `UnsafePointer<Void>`? I think it is more likely it is `UnsafePointer<UInt8>`, and the following compiles: ``` let data = Data(bytes: [1, 2, 3, 4]) data.withUnsafeBytes { (ptr: UnsafePointer<UInt8>) in myfunc(ptr) } ``` - Daniel > > data.withUnsafeBytes { (ptr: UnsafePointer<Void>) in myfunc(ptr) } // (B) > // warning: UnsafePointer<Void> has been replaced by UnsafeRawPointer > > which is understandable in the view of "SE-0107 UnsafeRawPointer API". > > The "Fix-it" replaces `UnsafePointer<Void>` by `UnsafeRawPointer`, and that > does not > compile anymore: > > data.withUnsafeBytes { (ptr: UnsafeRawPointer) in myfunc(ptr) } // (C) > // error: cannot convert value of type 'Void' to closure result type '_' > > because there is no `withUnsafeBytes()` method taking a > `(UnsafeRawPointer)->ResultType` > closure. > > > My questions are: > > 1. Why are (A) and (B) treated differently? > > 2. Is (A) "legal", or should one use some non-void pointer > > data.withUnsafeBytes { (ptr: UnsafePointer<Int8>) in myfunc(ptr) } // (D) > > (which feels wrong to me because it is converted back to a void pointer when > calling the function). > > 3. Or should there be a `withUnsafeRawPointer()` method which makes (C) > compile as > > data.withUnsafeRawBytes { (ptr: UnsafeRawPointer) in myfunc(ptr) } > > This would also allow to access the data at byte offsets more easily, e.g. > > data.withUnsafeRawBytes { ptr in > let u16 = ptr.load(fromByteOffset: 4, as: UInt16.self) > } > > Does that makes sense? > > Regards, Martin > > > > > > > > > > _______________________________________________ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users _______________________________________________ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users