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by chaeronanaut 1406 days ago
this pretty much summarises my opinion - one nitpick - i assume you meant "omit bounds and other checks", not "emit bounds and other checks" which seems to mean the opposite of what you're intending
2 comments
zozbot234 1406 days ago
Rust does emit bounds and other checks, though. Optimization passes can usually clear some of them away, but you'd need to check the assembly output to be sure.
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kitd 1406 days ago
Yes, that's "omit".

"Emit" means "to send out", eg "emit a strange noise", "emit radiation".

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Shish2k 1406 days ago
It is specifically both:

- trying to access an arbitrary element in a slice, the compiler will emit bounds checks (`if index > len: panic()`) to avoid an uncontrolled out-of-bounds memory access — https://godbolt.org/z/cbY5ebzvK (note how if you comment out the assert, the code barely changes, because the compiler is adding an invisible assert of its own)

- if the compiler can infer that `index` will always be less than `len`, then it will omit the bounds check — https://godbolt.org/z/TTashYnjd

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woodruffw 1406 days ago
Yes, thank you! That's an embarrassing typo!

(And thanks to the other person as well, who presumably deleted the same comment after seeing yours.)

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