Define SUCCESS and ERROR return type #21

Currently our API and internal function aren't very consistent about the return value. Whether should non-zero result be success or error? We should define the SUCCESS and ERROR symbol instead of return the raw integer.

is this any time pressure on this issue ?

ps. let me doubt about the good for first label (LOL)

Absolutely not time sensitive. It has been opened 13 years after all :-)

It's nice to have since the current API has two major incompatible return value styles, following C conventions:

1. Boolean where 1 is true and 0 is false
2. Result where -1 is fail and 0 is success

After working on this, you will learn

1. how to change the API signature and update the generate chewing.h header
2. how to expose rust types to C FFI safely
3. high level understanding of how each API treat return values

Need basic knowledge of C and Rust. I do not have any of that (cry)

why :

• incompatible interface works now ?
• any reason want to change it ?
• a simple function or interface example that make you decide to change it ?

I think I should make project build works, and learn FFI design for first.

This is why I doubt about the "good for first" label (LOL)

I can only found success / error definition in file /src/exn.rs :

pub(crate)traitResultExt{type Success;type Error: Error+Send+Sync+'static;}

is this the definition which is hope to been updated ?

there is a C header file which mention about return value : /capi/include/chewing.h. I am not sure if it is the file we need to consider.

We want to update the C interface.

I think we can move this definition

to somewhere after

and change them to public.

then use them in
90c949e75d/capi/src/io.rs, check comments like

/// The return value is 0 on success and -1 on failure.