[Git][reproducible-builds/reproducible-website][master] docs/stable-outputs: Add Rust section

[kpcyrd (@kpcyrd)]

kpcyrd pushed to branch master at Reproducible Builds / reproducible-website


Commits:
07558472 by kpcyrd at 2026-01-08T18:49:09+01:00
docs/stable-outputs: Add Rust section

- - - - -


1 changed file:

- _docs/stable_outputs.md


Changes:

=====================================
_docs/stable_outputs.md
=====================================
@@ -8,6 +8,8 @@ Data structures such as [Perl
 hashes](http://perldoc.perl.org/functions/keys.html), [Python
 dictionaries](https://docs.python.org/library/stdtypes.html#mapping-types-dict)
 and [sets](https://docs.python.org/library/stdtypes.html#set-types-set-frozenset),
+[Rust std::collections::HashMap and
+std::collections::Hashset](https://doc.rust-lang.org/stable/std/collections/index.html#iterators),
 or [Ruby Hash objects](https://ruby-doc.org/core/Hash.html) will list their keys
 in a different order on every run to limit [algorithmic complexity
 attacks](http://perldoc.perl.org/perlsec.html#Algorithmic-Complexity-Attacks).
@@ -47,6 +49,28 @@ Python users can similarly set the environment variable
 When set to a given integer value, orders in dictionaries and sets will be the
 same on every run.
 
+Rust
+----
+
+When iterating over the keys or entries of a `HashMap`, the order is [explicitly
+undefined](https://doc.rust-lang.org/stable/std/collections/struct.HashMap.html)
+and depends on a random seed:
+
+> By default, HashMap uses a hashing algorithm selected to provide resistance
+> against HashDoS attacks. The algorithm is randomly seeded, and a reasonable
+> best-effort is made to generate this seed from a high quality, secure source
+> of randomness provided by the host without blocking the program.
+
+Iterating over a HashMap can cause reproducible builds issue when:
+
+- done inside a `build.rs` file
+- done in a function that's directly or indirectly called from a `build.rs` file
+
+This can often be fixed by replacing `HashMap` with
+[`BTreeMap`](https://doc.rust-lang.org/stable/std/collections/index.html#use-a-btreemap-when).
+There's a [real-world example](https://github.com/gtk-rs/gtk-rs-core/pull/1840)
+of how this was fixed.
+
 General
 -------
 Beware that the [locale settings]({{ "/docs/locales/" | relative_url }})



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