C++ SDK or API - looking for collaborators

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1

Hi all,

I recently succeeded in compiling & deploying a C++ application that includes the standard library AND an external library, the nlohmann/json library.

For this, I am using a patched wasi-sdk compiler, which provides the clang++ compiler and the standard library, plus a home-grown IC API to get messages in/out via Candid.

The patched wasi-sdk is already open source, you can find it here.

But the IC-API, which I call icpp is not yet. It needs a bit more work. I had applied for a small grant to open source that IC API, because I think it can be a good starting point for full fledged C++ support.

My icpp API was reviewed by @roman-kashitsyn, and his feedback was that my approach is not ideal/not scalable, and he proposed an alternative approach to build a C++ SDK instead of an API.

I like to explore both approaches together with others that are interested in this topic, and potentially team up to apply for a grant together.

@domwoe already confirmed that funding would be available and a #cplusplus discord channel was opened.

Hope to see some of you there!

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2

Hi all,

After many months of work, the first development release, icpp 0.1.0, is now available.

You can find it here.

Look forward to your feedback.

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Good to see this. Cheers.

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Super cool @icpp! This also allows compiling many C++ libraries to be usable in the IC, right?

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Hi @domwoe ,
yes it indeed allows you to compile any C++ library to be usable in the IC, as long as

  • It is not using something unsupported by WebAssembly, like Exceptions.
  • It is not generating more than 300 Globals, because that is the current limit on the IC

Two examples I am using already:

  • ZipIterator:

    • Used inside icpp itself, when deserializing a Record, to sort multiple vectors based on field hash
    • I only had to out-comment usage of sstream, to avoid going over the max Globals

  • nlohmann/json:

    • I use it in our QA canister, to demonstrate how CandidTypeText can be used to send JSON back & forth over the wire
    • I only had to specify one compile flag available in the nlohmann/json library so it builds for environments without a file system. It compiled, linked and ran on the IC without any modifications:
      • cpp_compile_flags = [“-D JSON_HAS_FILESYSTEM=0”]

More and more C++ libraries can be compiled to WebAssembly, and with little effort it is then possible to use them on the IC, as long as the max Globals is not exceeded.

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