Links:
Moritz Systems Project Description URL: https://www.moritz.systems/blog/multiprocess-support-for-lldb/
Progress Report 1 URL: https://www.moritz.systems/blog/implementing-non-stop-protocol-compatibility-in-lldb/

Contact: Kamil Rytarowski <kamil@moritz.systems>
Contact: Michał Górny <mgorny@moritz.systems>

According to the upstream description, "LLDB is a next generation, high-performance debugger. It is built as a set of reusable components which highly leverage existing libraries in the larger LLVM Project, such as the Clang expression parser and LLVM disassembler."

FreeBSD includes LLDB in the base system. The previous sponsored projects improved LLDB, to make it a credible debugger for the base system, although it still has a few limitations compared to the contemporary versions of GNU GDB. This project started in April 2022. It aims to implement full support for debugging multiple processes simultaneously.

At the start of the project, LLDB featured very limited support for multiprocess debugging. The client featured support for debugging multiple independent processes simultaneously via maintaining multiple connections to different server instances. Thanks to our earlier work, the server was able to process fork(2) and vfork(2) calls and either detach the newly forked child and continue tracing the parent process, or detach the parent and follow the child (equivalent to GDB’s follow-fork-mode setting).

Once the project is finished, LLDB will be able to trace an arbitrary number of forked processes simultaneously (equivalent to GDB’s detach-on-fork off). Full support for the multiprocess extension to the GDB Remote Serial Protocol will be implemented, as well as partial support for the non-stop extension that will enable multiple processes to be resumed and stopped independently.

Sponsor: The FreeBSD Foundation