Question

我正在使用Swift-VectorBoolean库，该库当前在Swift 3.2上，尚未针对Swift 4.2进行更新，但仍应在Xcode 10上运行。在Xcode 9上运行该库可以正常工作。在Xcode 10上，它给出了一个我不确定如何解决的错误。这是有问题的功能：

typealias MyPathApplier = @convention(block) (UnsafePointer<CGPathElement>) -> Void
// Note: You must declare MyPathApplier as @convention(block), because
// if you don't, you get "fatal error: can't unsafeBitCast between
// types of different sizes" at runtime, on Mac OS X at least.

private func myPathApply(_ path: CGPath!, block: MyPathApplier) {
  let callback: @convention(c) (UnsafeMutableRawPointer, UnsafePointer<CGPathElement>) -> Void = { (info, element) in
    let block = unsafeBitCast(info, to: MyPathApplier.self)
    block(element)
  }

  path.apply(info: unsafeBitCast(block, to: UnsafeMutableRawPointer.self), function: unsafeBitCast(callback, to: CGPathApplierFunction.self))
}

错误在最后一行path.apply上，突出显示前unsafeBitCast：

Converting non-escaping value to 'T' may allow it to escape

我不确定如何修改此代码以消除错误，或者这不是Xcode 10的问题。它应该能够编译Xcode 3.2代码。甚至将代码库更新为Xcode 9中的Swift 4。，它仍然有相同的问题。

编辑：使用@Vyacheslav的答案更改它，使其可以编译，但会遇到运行时错误： “致命错误：不能在不同大小的类型之间使用unsafeBitCast”

在上面的示例中我没有包括的功能上方提供了一条注释：

// Note: You must declare MyPathApplier as @convention(block), because
// if you don't, you get "fatal error: can't unsafeBitCast between
// types of different sizes" at runtime, on Mac OS X at least.

我仍然不知道需要在此处进行哪些更改以确保其构建，并且我们也没有遇到运行时错误。

Answer 1

使用

private func myPathApply(_ path: CGPath!, 
    block: @escaping @convention(block) (UnsafePointer<CGPathElement>) -> Void) {

}

@noescape现在默认为

Xcode 10 Swift构建错误：“将非转义的值转换为'T'可能允许其转义”

1 个答案: