-sys library design principles

In general, the -sys library should keep only unsafe C interface bindings and should not have redundant security abstractions.

However, for a pure Rust SDK like wasmedge-rs that we will eventually build, there should not be too many C binding interfaces. So, the wasmedge-sys library uses a thin layer of Rust wrappers, exposing only the appropriate interfaces for the upper layer of wasmedge-rs to abstract a more usable pure Rust SDK.

The interfaces exposed by the -sys library are supposed to be stable. That is, when the C interface changes, only the -sys library needs to be changed, not the upper-layer SDK.

Library interface description

• Error handling: return ErrReport structures uniformly, and do further Rust-style error handling in the upper-level -wasmedge-rs SDK.
• Incorporate basic types into the -sys library, e.g. Strings/Value etc., which the upper level SDK just needs to use.
• Configuration/module loading/creating VMs/starting VMs to compute return results, these are put into the -sys library as the base interface for the SDK.
• The base interface, which involves creation or initialization, uses basic "encapsulation" and is not open to downstream modifications to ensure the stability of the base interface.
• The corresponding C-API header file and the corresponding Rust binding interface are recorded in the Dosc directory as documentation.