It should be noted that Objective-C code is presumably a lot less prone to memory safety issues than C code on average, especially since Apple introduced Automatic Reference Counting (ARC). For example:

• Use-after-frees are avoided by ARC

• Null pointer dereferences are usually safe (sending a message to nil returns nil)

• Objective-C has a great standard library (Foundation) with safe collections among many other things; most of C's dangerous parts are easily avoided in idiomatic Objective-C code that isn't performance-critical

But a good part of Apple's Objective-C code is probably there for implementing the underlying runtime, and that's difficult to get right.

I found the evolution of programming languages article you sourced very interesting.

Just to summarize the article, it shows that writing completely new code in memory safe language, while maintaining non-memory safe code, results in a steep reduction in memory safe errors overtime even though it results in an overall increase in unsafe code. It says that most memory safe vulnerabilities come from completely new code not maintained code and thus argues you can get the most of the benefits of memory safe code without rewriting your entire code base, which I think is the main takeaway from the article.

I’m not sure that’s totally happening in MacOS from reading your article, but it kind of is, so I think my hypothesis is correct that MacOS will likely have less vulnerabilities as it transitions many newer projects to swift although its important to note that important vulnerable projects such as webkit are still written in C++.