Rust FFI + Mojo Package: Released as an independent package using mojopkg, then importing it results in a compilation error

[henry]

Problem:

Publish a Mojo package that depends on a Rust FFI binary library, then add the Mojo package to a project and encounter a compile error, unable to find the Mojo package.

Details:

1. The binary library compiled and released by the subproject uuid-ffi based on the rust ffi implementation is libuuid_ffi, and it is completely normal to introduce this library into the subproject uuid-mojo as a dependency. The written uuid-mojo module, in src/main.mojo, is imported and used as source code, and the compilation is completely normal and as expected.

2. However, when you publish uuid-mojo as a separate mojopkg package as uuid, and then add the package to a project and then compile it, it will cause a crash during compilation and will not work properly.

Related Projects: (uuid-rs to uuid-mojo)

• Here’s a complete example project, using uuid-rs as the source project, binding it into an independent uuid mojo package via rust ffi.

uuid-ffi(base on uuid-rs + rust ffi):

disc/packages/uuid-ffi at main · better-mojo/disc

uuid mojo:

disc/packages/uuid-mojo at main · better-mojo/disc

mojo example:

disc/packages/uuid-mojo/examples/try-uuid at main · better-mojo/disc

Published Pacages:

uuid ffi:

• libuuid_ffi - better-ffi

uuid mojo:

• uuid - better-mojo

Reproduce errors:

• This example package is small enough that only 2 sets of APIs are exported, and the implementation is very simple.

• Anyone, based on the code I’ve provided, can easily reproduce the compile-time error (when imported as a standalone mojo package).

• Taskfile.yml has a full build script in it, feel free to ask me if you need any further information. I’ll keep an eye on how this issue progresses.

error logs:

packages/uuid-mojo/examples on  main on ☁️   
❯ ls
 try-uuid   try_uuid.mojo   uuid.mojopkg


packages/uuid-mojo/examples on  main on ☁️   
❯ magic run mojo run try_uuid.mojo
Please submit a bug report to https://github.com/modular/mojo/issues and include the crash backtrace along with all the relevant source codes.
Stack dump:
0.      Program arguments: /Users/dev/Documents/iSpace/better-mojo/disc/packages/uuid-mojo/.magic/envs/default/bin/mojo run try_uuid.mojo
mojo crashed!
Please file a bug report.
[88785:34351290:20250224,140458.803901:ERROR directory_reader_posix.cc:42] opendir ~/better-mojo/disc/packages/uuid-mojo/.magic/envs/default/share/max/crashdb/attachments/dc65d4f7-82ec-4c45-b4ed-c1687097c75d: No such file or directory (2)
[88785:34351289:20250224,140458.860248:WARNING crash_report_exception_handler.cc:257] UniversalExceptionRaise: (os/kern) failure (5)


❯ magic run mojo build try_uuid.mojo -o main
Please submit a bug report to https://github.com/modular/mojo/issues and include the crash backtrace along with all the relevant source codes.
Stack dump:
0.      Program arguments: ~/better-mojo/disc/packages/uuid-mojo/.magic/envs/default/bin/mojo build try_uuid.mojo -o main
mojo crashed!
Please file a bug report.
[90602:34354350:20250224,140542.079822:WARNING crash_report_exception_handler.cc:257] UniversalExceptionRaise: (os/kern) failure (5)

aslo, normal case:

disc/packages/uuid-mojo on  main on ☁️   
❯ ls
 examples   magic.lock   mojoproject.toml   output   readme.md   recipes   src   Taskfile.yml   test

disc/packages/uuid-mojo on  main on ☁️   
❯ magic run mojo run src/main.mojo 

rust > uuid v4: 5508f795-31c9-4b37-beee-559de51fd233
rust > freeing string: "5508f795-31c9-4b37-beee-559de51fd233", raw: "5508f795-31c9-4b37-beee-559de51fd233"
rust > uuid v7: 01953691-84c3-7c61-927b-eb8e485dec64
rust > freeing string: "01953691-84c3-7c61-927b-eb8e485dec64", raw: "01953691-84c3-7c61-927b-eb8e485dec64"
rust > uuid v4: 7d50274a-c2db-41d3-ba35-4a6295f8c43a
rust > uuid v7: 01953691-84c3-7c61-927b-eb97d1b48228
5508f795-31c9-4b37-beee-559de51fd233
01953691-84c3-7c61-927b-eb8e485dec64
7d50274a-c2db-41d3-ba35-4a6295f8c43a
01953691-84c3-7c61-927b-eb97d1b48228

• example

[henry]

By the way:

• The uuid-mojo library, if used in a way that copies the source code, is perfectly normal.

• This project(uuid-mojo) gives several ways to convert the interface of Rust FFI, and welcomes more people to refer to this idea and extend more rust libraries for Mojo to use.

• Based on the Rust project GitHub - getditto/safer_ffi: Write safer FFI code in Rust without polluting it with unsafe code, it’s very easy to make FFI libraries.