Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust

Kaz Kylheku <643-408-1753@kylheku.com> writes:
>On 2025-05-14, arnold@freefriends.org <arnold@freefriends.org> wrote:
>> [Rust] relies on compiler analysis instead.
>
>How would it be safe if you could write a Rust program that asks the
>user to input a random decimal number, and then uses it an index to
>access an array, without any check?


I don't know if Rust does it this way, but it could reject a program
that does a[i] if it cannot prove that i is an allowed index for a.
For your example, a program like this would be rejected:


input i
print a[i]


(using what little I remember from BASIC syntax because I don't know the Rust
syntax:-). If you want the compiler to accept it, you could write


input i
if i < length[a] then
    print a[i]
else
    print "index out of range"
endif


- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/
[I believe that Rust does runtime checks unless it can prove at compile time that they're not needed.
It has a fancy exception system to catch access violations. -John]

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