Sponsor 38: https://trac.torproject.org/projects/tor/wiki/org/sponsors/Sponsor38

We've been primarily focused on prototyping the new process-based simulation architecture https://github.com/shadow/shadow/milestone/16:

- General libc + syscall interposition plumbing is fairly stable now, including marshaling pointer arguments across the Shadow/Plugin process boundary, in both the ptrace and the LD_PRELOAD interposition mechanisms.

- Settled on a logging design and implemented it. In particular we needed to address the problem of logging from our "shim" code that's LD_PRELOADed into the plugin's process. Since it's no longer in Shadow's process, we can't directly use Shadow's logger, which references internal Shadow data structures and in-memory queues. To further complicate things, some code runs both inside Shadow and inside the LD_PRELOADed library, and that code should use Shadow's logger when and only when running inside Shadow. We developed a simple plugabble logger that writes to stdout by default, uses Shadow's logging when running inside Shadow, and a "shim logger" when running inside the LD_PRELOADed shim. This also allows us to use the same logging API inside tests and support libraries.

- We've gotten more syscalls and parts of libc implemented, including syscalls from unistd.h and most of the socket.h syscalls. These are the basic interfaces used by almost every network program to handle communication and file descriptor i/o. We are nearly ready to start running some multi-process networking benchmarks.

We've also made some general improvements on the public Shadow branch https://github.com/shadow/shadow/pulls?page=2&q=is%3Apr+is%3Aclosed+upda...:

- Added both debug and release builds to our continuous integration test matrix, helping us catch more bugs before they get merged.

- Got rid of the monolithic shadow.h header, substantially speeding up incremental builds, and improving compatibility with code analysis tools.

- Documentation cleanup and additions, including adding contributor guidelines.

- Reduced flakiness in multi-process networking tests by moving away from hard-coded server ports.

- Added additional integration tests to cover functionality being implemented in the new process-based model.

- Migrated from Python 2 to 3.

We also spent some time strategizing about how to use Github "milestones" and "issues" to help us plan and prioritize development work and to keep the community updated on our progress. We are still in the early stages and hope to make more effective use of these planning tools over time.

Finally, we're thrilled to welcome Steve Engler to the project. Steve is starting today: Monday, June 1.