Example: How to terminate a program via an Import

[syrusakbary]

From the Slack channel, we got this question:

from the C api is there a way to signal that the wasm client application should terminate
suppose my wasm program calls fancy_exit( some parameters );
which is an import provided by the host.
I dont want to return to executing code in the wasm client after processing the exit call

Right now, this is possible via the Rust API (WASI is using this strategy):

1. First, an import is provided - https://github.com/wasmerio/wasmer/blob/master/lib/wasi/src/lib.rs#L297
2. This import, when getting called raises an error - https://github.com/wasmerio/wasmer/blob/master/lib/wasi/src/syscalls/mod.rs#L2493-L2497
3. The application listens from this error when starting the instance - https://github.com/wasmerio/wasmer/blob/master/lib/cli/src/commands/run/wasi.rs#L69-L76

For closing this issue we will need:

• Complete Example in Rust (without WASI)
• Complete example in C