[tor-bugs] #23881 [Core Tor/Tor]: Implement a way to utilise tor's logging system from Rust code

[Tor Bug Tracker & Wiki]

#23881: Implement a way to utilise tor's logging system from Rust code
------------------------------+------------------------------------
 Reporter:  isis              |          Owner:  chelseakomlo
     Type:  enhancement       |         Status:  assigned
 Priority:  High              |      Milestone:  Tor: 0.3.3.x-final
Component:  Core Tor/Tor      |        Version:
 Severity:  Normal            |     Resolution:
 Keywords:  rust, rust-pilot  |  Actual Points:
Parent ID:                    |         Points:  3
 Reviewer:                    |        Sponsor:
------------------------------+------------------------------------

Comment (by chelseakomlo):

 Ok, see the merge request on gitlab here:
 https://oniongit.eu/network/tor/merge_requests/7

 This PR creates a minimal implementation for Rust modules to log using
 tor's existing logger.

 One issue that I ran into is that log levels/domains are defined as macros
 in C. I redeclared a small subset of these as constants- if this is the
 approach that we want to take, I can fill out the remainder of necessary
 constants. Another alternative is to define log level/log domain macros as
 constants in C.

 In order to run module-level Rust tests without linking to C, it is
 necessary to "stub" out direct calls to C functions. This PR adds a
 "testing" feature in order to optionally compile no-op implementations for
 testing. (The approach of "write C integration tests and test Rust in
 isolation" is an approach taken by Servo, although it would be great to
 get Rust people's eyes on this to double check how I've done this).

 Looking forward to feedback and suggestions how to improve!

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23881#comment:8>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online