Rust in the 6.2 kernel [LWN.net]

Rust in the 6.2 kernel

Posted Dec 12, 2022 21:04 UTC (Mon) by oconnor663 (guest, #119484)
In reply to: Rust in the 6.2 kernel by farnz
Parent article: Rust in the 6.2 kernel

You (farnz) probably already know this but I think it's worth adding: Not only deallocated, but also reallocated. Calling .push_back() or .append() on the original string also potentially invalidates a string_view.

It could be totally fair to describe these as niche issues that don't affect most callers of string_view. But I don't agree with calling someone a "liar" because you (ncm) think it's niche. Or if these issues are new to you, great! None of us is ever done learning.

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Rust in the 6.2 kernel

Posted Dec 13, 2022 11:14 UTC (Tue) by farnz (subscriber, #17727) [Link]

Yes - apologies for being unclear. I think of reallocations as an optimized form of allocate, copy and deallocate, so it's implicit to me that reallocation can invalidate the original string.

At heart, this is the same problem as iterator invalidation. You have a reference to some underlying data, and changes to that underlying data can result in your reference no longer being valid. C++ has no compiler checks for reference validity, and relies on the programmer not getting it wrong; this makes some sense, since any check for reference validity is going to be conservative and thus will need overriding from time to time, but the history of "rely on the programmer not getting it wrong" suggests it's not a great decision.