Implement compatibility checks between munlib and runtime

[baszalmstra]

Problem

Currently, the runtime tries to load a *.munlib with the assumption that the ABI memory layout of the *.munlib matches its own ABI version. This can cause undefined behaviour when it tries to load a *.munlib with a different ABI version.

Solution

By including an ABI version in the *.munlib, the runtime can gracefully fail - reporting an error to the end user.

In the future - once we support backwards compatibility, we can even support loading of several different ABI versions using this functionality.

Tasks

• add an integer ABI_VERSION constant to the mun_abi crate.
• generate a get_version IR function
• export the get_version function
• in the runtime, call the get_version function and verify that the runtime's mun_abi::ABI_VERSION is compatible.
• (bonus) add a constant with the get_version function name (and other API functions) to the mun_abi crate and use that constant in both the mun_codegen and mun_runtime crates - to avoid discrepancies.

Good first issue process:

• read our contributing guidelines
• claim this issue (assign yourself or comment below)
• implement the feature and start a Pull Request with in the description: closes Implement compatibility checks between munlib and runtime #188.

If this is your first PR, welcome 🎉 😄

[MineBill]

I would like to tackle this issue and implement the feature. This will be my first ever PR.

[Wodann]

Welcome and thank you for working on this PR. If you have any questions, please let us know.

[MineBill]

After implementing this, the following tests fail:

tests::abi_is_fresh
tests::runtime_capi_is_fresh

They require me to update the abi and the runtime-capi but doing so requires me to download both the ffi and the abi-c submodules. What should i do?

[Wodann]

You should always download the submodules, otherwise the tests will fail. Our install instructions describe how to do it, but it's just a single command:

git submodule update --init --recursive

[Wodann]

Exemplary work! Really quick workflow from claiming the issue, to submitting a PR, and incorporating recommended changes. Well done 👍

We look forward to your next contribution