If you stay in pure swift, it's much harder to segfault, but it's still possible, mainly due to the amount of objC code you interact with. Today, it's not reasonable to expect a swift programmer to be proficient without knowing objC, the way it's reasonable for a Java programmer to not know C.
The segfault I hit yesterday had to do with a CoreData API that didn't retained its argument, when I assumed it did. The bug doesn't appear when compiling with -Onone, but does appear in -O. Compiler flags are another place where Swift is still very much in C-land, rather than Java/Python/Ruby land. You still need to understand the C compilation model, and e.g. getting your ARC flags wrong in a cocoapod will still cause crashes.
To be clear, swift is a big improvement over objC, but you can't pretend it's a VM managed language.
>Memory safety does not require VM management (or so Rust is trying to prove).
I agree, with a few qualifications. I think Haskell has already proved it's possible.
I think Swift + ARC isn't a strong enough guarantee of memory safety for two reasons:
1) Swift has to interact with a huge amount of objC code, of varying degrees of quality (some Apple code, some OSS code via cocoapods). Swift itself would be much safer if all objC was rewritten in Swift.
2) ARC isn't as strong a guarantee as either GC or Rust's pointer semantics. For example, it's easy to hold weak references to something you thought was retained, and then dereference an invalid pointer.
So yes, you can have a memory safe language without a VM, but I think you need GC and/or much stronger pointer semantics, ala rust.
The segfault I hit yesterday had to do with a CoreData API that didn't retained its argument, when I assumed it did. The bug doesn't appear when compiling with -Onone, but does appear in -O. Compiler flags are another place where Swift is still very much in C-land, rather than Java/Python/Ruby land. You still need to understand the C compilation model, and e.g. getting your ARC flags wrong in a cocoapod will still cause crashes.
To be clear, swift is a big improvement over objC, but you can't pretend it's a VM managed language.