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Wild – A fast linker for Linux

(github.com)
383 points hkalbasi | 3 comments | 24 Jan 25 16:25 UTC | HN request time: 0.425s | source
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devit ◴[24 Jan 25 16:49 UTC] No.42814926[source]▶
I think the optimal approach for development would be to not produce a traditional linked executable at all, but instead just place the object files in memory, and then produce a loader executable that hooks page faults in those memory areas and on-demand mmaps the relevant object elsewhere, applies relocations to it, and then moves it in place with mremap.

Symbols would be resolved based on an index where only updated object files are reindexed. It could also eagerly relocate in the background, in order depending on previous usage data.

This would basically make a copyless lazy incremental linker.

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jjmarr ◴[24 Jan 25 18:06 UTC] No.42815660[source]▶
Isn't this how dynamic linking works? If you really want to reduce build times, you should be making your hot path in the build a shared library, so you don't have to relink so long as you're not changing the interface.
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1. hinkley ◴[24 Jan 25 20:22 UTC] No.42816581[source]▶
But do rust’s invariants work across dynamic links?

I thought a lot of its proofs were done at compile time not link time.

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2. pas ◴[24 Jan 25 23:46 UTC] No.42818056[source]▶
The proof can be done on the whole code (in memory, incremental, etc), and then the modules emitted as dynamically loadable objects.
3. Nullabillity ◴[25 Jan 25 00:25 UTC] No.42818263[source]▶
Yesn't.

Rust is perfectly happy to emit/use dynamic links.[0] It's just that the primary C use case (distributing and updating the main app and its libraries separately) ends up being unsafe since Rust's ABI is unstable (so compiler versions, libraries, etc must match exactly).

Avoiding static relinking during development is pretty much the use where it does work. In fact, Bevy recommends this as part of its setup guide![1]

Practice paints a slightly less rosy picture, though; since the feature is exercised quite rarely, not all libraries work well with it in practice.[2]

[0]: https://doc.rust-lang.org/reference/linkage.html#r-link.dyli...

[1]: https://bevyengine.org/learn/quick-start/getting-started/set...

[2]: For example, https://github.com/linebender/bevy_vello/issues/84