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

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#23881: Implement a way to utilise tor's logging system from Rust code
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 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:
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Comment (by chelseakomlo):

 Replying to [comment:5 nickm]:
 > So my first thought is to take this approach:
 >    * Refactor the C a bit, though, so that there is a tor_log_string()
 function taking a severity, domain, and message.  It should work the same
 as `tor_log(severity, domain, message);`, but instead it should be safe to
 call it function with strings containing `%`.  (I can write this one if
 you want: it will involve refactoring `logv` a little.

 This sounds great- I was hesitant to add a bunch of functionality to Rust
 just to make it compatible with the existing C api. If you have time to do
 this, that would be great! Otherwise I can take a stab at it this week.

 >    * Expose that function to rust.
 >    * Write a single rust macro that takes severity, domain, message, and
 some format arguments, and uses the `format!` mechanism to generate the
 log message.

 This is approximately what I have, with the ability to optionally compile
 with a no-op implementation (for running tests at the rust module level).

 > Optionally afterwards:
 >    * Expose a view of `log_global_min_severity` to rust, maybe via a
 function.
 >    * Update the rust macro to compare `log_global_min_severity` to the
 declared severity, and avoid formatting the message if no logs actually
 want it.
 This sounds great- we can do this either in this ticket or an enhancement.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23881#comment:6>
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