How to embed in C++? How to store secret state?

[codefishd]

Greetings

I want to use wasmtime or another runtime in a C++ app to secure calls to complicated functions.
Is there an example for that?

In particular ----> how can a webassembly function call functions from the main app with secret state only stored in the app (-- not visible from webassembly for security --)? How to implement wrappers like wasmerio/wasmer#925 with wasmtime? Is it possible?

[yurydelendik]

@codefishd The wasmtime implements wasm-c-api , see e.g. https://github.com/WebAssembly/wasm-c-api/blob/master/example/callback.c . AFAIK the wasm-c-api is (being) implemented for V8, wasmtime, wabt interpreter.

to secure calls to complicated functions

Can you explain what do you mean under "complicated functions"?

how can a webassembly function call functions from the main app with secret state only stored in the app

Is it similar to host info attached to the embedded object?

[jedisct1]

If I understand correctly, and if you don't specifically need to run code compiled to WebAssembly, the Google Sandboxed API may do what you are looking for.

[tschneidereit]

I think @yurydelendik's answer about callbacks should address this, so I'll close this issue. @codefishd, feel free to reopen if you disagree and can further clarify your use case and why it's not addressed by closure callbacks.