"A consequence of this principle is that every occurrence of every subscript of every subscripted variable was on every occasion checked at run time against both the upper and the lower declared bounds of the array. Many years later we asked our customers whether they wished us to provide an option to switch off these checks in the interests of efficiency on production runs. Unanimously, they urged us not to--they already knew how frequently subscript errors occur on production runs where failure to detect them could be disastrous. I note with fear and horror that even in 1980 language designers and users have not learned this lesson. In any respectable branch of engineering, failure to observe such elementary precautions would have long been against the law."
-- C. A. R. Hoare, Turing award lecture in 1981, http://cacm.acm.org/magazines/1981/2/10949-the-emperors-old-...
> I do wonder if Apple is considering re-writing any of these core services in a safer language.
Apple already uses C++ for device drivers, which allows for more safety oriented programming as straight C.
In any case, even if it isn't fully ready today, they view Swift as a C and Objective-C replacement in the long term.
"Fast. Swift is intended as a replacement for C-based languages (C, C++, and Objective-C). " -- https://swift.org/about/
"Swift is a successor to both the C and Objective-C languages." -- https://developer.apple.com/swift/
The dock and launchd in Sierra were rewritten in Swift.