How to add lib.rs to a cxx bin crate package? about cxx

[nneesshh]

and here is my full project:
hello_cxx.zip

[nneesshh]

Finally I move the bridge code into the lib.rs, and change the build.rs
from "cxx_build::bridge("src/main.rs")" to "cxx_build::bridge("src/lib.rs")",
it works.

It should be a purposely design because there is no way to share if you write your ffi code in bin crate. It should be in lib crate. Am I right?

[nneesshh]

Add "l static=cxxbridge-demo" to lib crate is not the proper way, it still doesn't work if the cpp code in a extern cpp lib.
Is there a rule says that must only one bin crate exist in the package?

[nneesshh]

see #1195 (comment) and rust-lang/cargo#8919 (comment)

"
This is currently expected behavior in Cargo. Cargo links the native libraries to the Rust library but then doesn't link them to the binary, assuming that the Rust library is linked to in the binary. If you add extern crate demo to your src/main.rs does it work?
"

They all says "extern crate hello_cxx;". I test and found: It is not necessay. It only works If the lib crate and bin crate are not in same package.

Yes, one native library can only be added to one crate?
The limitation seems come from "build.rs" only works for one crate