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Re: Rust reprodubility -- .rmeta and shadow-rs

From: Ludovic Courtès
Subject: Re: Rust reprodubility -- .rmeta and shadow-rs
Date: Thu, 30 Jun 2022 13:35:15 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux)


Maxime Devos <> skribis:

> There was some mail about irreproducibility in Rust, but I couldn't
> find it anymore.  Anyway, I found a potential cause: rust-shadow-rs
> embeds timestamps (even though it nominally respects
> SOURCE_DATE_EPOCH???) and the ordering of definitions it generates is
> based on a hash map (and hence, irreproducible).

I found these:

> The crate id is based on a hash over the source code, so this
> irreproducibility can cause build failures if substitutes are used.
> By removing the time stamp and sorting the definitions, 'nushell'
> successfully built on whereas it previously failed to
> build on but built successfully locally (with
> antioxidant), and IIRC the (antioxidated) 'rust-nu-command' is now
> reproducible:
> Anyway, here the patch I used:
>     ("rust-shadow-rs"
>      ,#~((add-after 'unpack 'fixup-source-date-epoch
>          (lambda _
>            ;; TODO: it nominally supports SOURCE_DATE_EPOCH, yet something 
> things go wrong,
>            ;; as the still contains the unnormalised time stamp ...
>            ;; For now, do a work-around.
>            (substitute* '("src/" "src/")
>              (("BuildTime::Local\\(Local::now\\(\\)\\)\\.human_format\\(\\)")
>               (object->string "[timestamp expunged for reproducibility]"))
>              (("time\\.human_format\\(\\)")
>               "\"[timestamp expunged for reproducibility]\".to_string()")
>              (("time\\.to_rfc3339_opts\\(SecondsFormat::Secs, true)")
>               "\"[timestamp expunged for reproducibility]\".to_string()")
>              (("time\\.to_rfc2822\\(\\)")
>               "\"[timestamp expunged for reproducibility]\".to_string()"))))
>        (add-after 'unpack 'more-reproducibility ;; by default, it uses a 
> hashmap, leading to an irreproducible ordering in and hence an 
> irreproducible .rmeta (TODO: upstream?)
>          (lambda _
>            (substitute* "src/" ; sort
>              (("\\(k, v\\) in self\\.map\\.clone\\(\\)")
>               "(k, v) in 
> std::collections::BTreeMap::from_iter(")
>              (("self\\.write_const\\(k, v\\)") "self.write_const(k, 
> v.clone())")
>              (("self\\.map\\.keys\\(\\)") 
> "std::collections::BTreeSet::from_iter("))))))
> Maybe that was the cause?

You mean this issue you identified could have been the cause of
reproducibility issues found in other Rust packages?

Anyway, it looks like the snippet above should be applied to
‘rust-shadow-rs’ in current ‘master’, no?


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