[experiment] null-terminate track_caller strings

[saethlin]

Trying to evaluate the compile-time/binary size impact of doing this. I suspect it's not measurable, but good to check.

The implementation here is kind of bad. I tried doing two strategies at once and it went predictably.

r? ghost

[saethlin]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 4bd011f with merge d6eee0b...

[bors]

☀️ Try build successful - checks-actions
Build commit: d6eee0b (d6eee0bf26e73b842d846461e8c59911943a4b5d)

[rust-timer]

Finished benchmarking commit (d6eee0b): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results (primary -2.2%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.2%	[-2.2%, -2.2%]	1

Binary size

Results (primary 0.0%, secondary 0.0%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	8
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	22
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	8

Bootstrap: 781.235s -> 780.531s (-0.09%)
Artifact size: 333.60 MiB -> 333.57 MiB (-0.01%)