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

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From	anton@mips.complang.tuwien.ac.at
Newsgroups	comp.compilers
Subject	Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust
Date	Thu, 15 May 2025 07:48:12 +0000
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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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Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust John R Levine <johnl@taugh.com> - 2025-05-09 12:27 -0400
  Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust Derek <derek-nospam@shape-of-code.com> - 2025-05-13 21:30 +0100
    Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust arnold@freefriends.org - 2025-05-14 08:21 +0000
      Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-14 20:01 +0000
        Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust anton@mips.complang.tuwien.ac.at - 2025-05-15 07:48 +0000
      Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust George Neuner <gneuner2@comcast.net> - 2025-05-15 11:52 -0400
      Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust cross@spitfire.i.gajendra.net - 2025-05-16 15:42 +0000
        Re: Paper: PR2: Peephole Raw Pointer Rewriting with LLMs for Translating C to Safer Rust Kaz Kylheku <643-408-1753@kylheku.com> - 2025-05-16 17:57 +0000

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