82 lines
2.3 KiB
Markdown
82 lines
2.3 KiB
Markdown
## Integrations
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---
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This repository is a small Rust/Haskell interop demo.
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The current project demonstrates communication in both directions:
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- Haskell calling into Rust through a C ABI exposed by the Rust crate
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- Rust calling back into Haskell through a Cabal `foreign-library`
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The code is intentionally small. The goal is to show the main integration mechanics and the main failure points without adding code generation or a large build stack.
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## What The Demo Contains
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- `rust/` - Rust exports a C ABI for Haskell and provides a CLI path that loads and calls the Haskell shared library
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- `haskell/` - Haskell contains a small Cabal project with:
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- an executable that calls Rust
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- a shared foreign library that Rust calls
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- small pure tests for the shared Haskell-side logic
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The boundary is deliberately C-shaped:
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- integers
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- a shared struct layout
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- owned C strings with explicit free functions on each side
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## Why The Build Uses Both Static And Shared Libraries
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This demo uses different library styles for the two directions because that keeps each path simpler:
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- Haskell -> Rust uses the Rust crate as a static library
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- Rust -> Haskell uses a Haskell shared foreign library that Rust loads at runtime
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That is not the only possible design. It is just a practical one for a two-way demo.
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## Build And Run
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Build the Haskell project and the Rust library it links against:
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```sh
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make haskell-build
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```
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Run the Haskell -> Rust demo:
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```sh
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make haskell-run
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```
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Run the Rust -> Haskell demo:
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```sh
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make rust-calls-haskell
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```
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You can also run the underlying commands directly:
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```sh
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cargo test
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```
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```sh
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cd haskell
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CABAL_DIR=$PWD/../.cabal XDG_STATE_HOME=$PWD/../.cabal/state XDG_CACHE_HOME=$PWD/../.cabal/cache XDG_CONFIG_HOME=$PWD/../.cabal/config cabal test --project-file=cabal.project
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```
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## What This Project Demonstrates
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- the ABI boundary must stay simple and explicit
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- Rust and Haskell do not share ownership rules automatically
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- struct layout must match on both sides
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- Rust calling Haskell is the harder direction because it must initialize the GHC runtime correctly
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- build tooling is part of the integration problem, not just an implementation detail
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### License
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This project is licensed under either of these:
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* MIT License (see [LICENSE-MIT](LICENSE-MIT))
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* Apache License, Version 2.0 (see [LICENSE-APACHE](LICENSE-APACHE))
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