ref(logging): provide alternative log output sinks

[armcknight]

I need alternative destinations for certain logging tasks besides just NSLog, like printf or files. This refactors the current logging API to allow for providing a combination of those three, defaulting to file and NSLog.

It converts SentryLog's API from class-bound methods to instance-bound, which simplifies a couple things in the tests and the codebase, and will allow for having more than one logger instance, so that the other places that need an alternative can set up their own logger.

The default logging setup is still provided via a singleton, which we already did implicitly, so this is just made more explicit.

Helps with #4020; #skip-changelog

TODO:

• expose C functions for writing to printf() and files (using write()) so that contexts that require async-safety can call them directly, bypassing the objc apparatus. Need to figure out how to make this play nicely with configured log levels.

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code can easily blow up and is hard to test. We had severe bugs in the past. Be extra careful when changing these files, and have an extra careful look at these:

• Sources/Sentry/SentrySubClassFinder.m

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1207.21 ms	1217.72 ms	10.52 ms
Size	21.58 KiB	680.75 KiB	659.17 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
b6ba04e	1230.48 ms	1253.20 ms	22.72 ms
a176fc4	1250.29 ms	1257.88 ms	7.59 ms
b4f8dba	1343.92 ms	1362.96 ms	19.04 ms
9ae806a	1243.84 ms	1256.22 ms	12.39 ms
afd1a08	1207.78 ms	1223.44 ms	15.66 ms
4bca912	1252.42 ms	1260.06 ms	7.64 ms
2ce582e	1238.98 ms	1259.66 ms	20.68 ms
45d3ca5	1238.53 ms	1263.09 ms	24.55 ms
aa4eddf	1228.21 ms	1236.72 ms	8.51 ms
5d6ce0e	1206.72 ms	1228.67 ms	21.95 ms

App size

Revision	Plain	With Sentry	Diff
b6ba04e	20.76 KiB	414.44 KiB	393.68 KiB
a176fc4	22.84 KiB	403.24 KiB	380.39 KiB
b4f8dba	21.58 KiB	614.87 KiB	593.29 KiB
9ae806a	21.58 KiB	616.14 KiB	594.56 KiB
afd1a08	22.84 KiB	402.57 KiB	379.72 KiB
4bca912	22.85 KiB	411.14 KiB	388.29 KiB
2ce582e	22.85 KiB	410.97 KiB	388.12 KiB
45d3ca5	20.76 KiB	427.54 KiB	406.78 KiB
aa4eddf	21.58 KiB	544.86 KiB	523.28 KiB
5d6ce0e	22.85 KiB	405.38 KiB	382.53 KiB

[philipphofmann]

Is it possible to write the new classes in Swift?

[armcknight]

Is it possible to write the new classes in Swift?

The next step was going to be factoring out the implementation into C functions that can be called outside of the objc path so we can use them from async contexts, so I'm not sure.

[armcknight]

I'm going to close this and work on something slightly different related to logging, because this is getting too deep into file-based logging issues like log size/rotation etc that I didn't initially plan to take on. If we want file-based logging in the future, we should investigate forking an existing solution.

What I really wanted was to be able to use an async-safe logger from more of the profiling code, since there's still some stuff there that winds up using NSLog, which is unsafe from the logging thread.

What I'm going to do there is repurpose the crash reporter logger and reuse it there.