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A comment on Cross-platform Rust rewrite of the GNU coreutils. Parent comment

Re:Cross-platform Rust rewrite of the GNU coreutils by Gankro on Tuesday March 22, 2016 @07:45PM (#11340882)
> Even specifying that they have a new arbitrary value on each access would be a big improvement over the status quo.

This is approximately what LLVM describes undef as, and it indeed leads to nasal demons. This description enables a single value to both pass a bounds check, and then subsequently go out of bounds!

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Re:Cross-platform Rust rewrite of the GNU coreutils by Dylan16807 on Tuesday March 22, 2016 @08:04PM (#11340977)
You're right, in certain cases it would still cause trouble, but it would be a lot fewer cases than 100%. Reading only once would be safe, and passing it to another functions would make a variable that can no longer change unexpectedly.
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Re:Cross-platform Rust rewrite of the GNU coreutils by dbaupp on Tuesday March 22, 2016 @08:51PM (#11341256)
Unless the function is inlined/the compiler can deduce that the variable is undef.

(Of course, you could define it to work, but I would suspect that would make this sort of value much less useful.)

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