perf(chat): use reentrant local time for chat timestamps

The open chat thread called std::localtime at least twice per message
per frame (two day keys for grouping), and more for day separators and
time labels. On glibc every call re-checks the timezone with a stat of
/etc/localtime. The chat time helpers now use util::localTime() from
the new util/local_time.h: localtime_r (localtime_s on Windows), with
no per-call timezone check and no shared static result buffer.

glibc's localtime_r reads the timezone only once, so local_time.h also
adds util::refreshTimezone() (tzset) for caches to call when they
rebuild. Nothing calls it yet; its first caller is the chat thread's
grouping-flags cache in the next commit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

This commit is contained in:

DanS

2026-10-10 09:50:03 -05:00

co-authored by

Claude Opus 5.5

parent e45f4c7d90

commit a69380817e

4 changed files with 62 additions and 21 deletions

									
										CMakeLists.txt
									
		+1
		
												View File
												
				@@ -713,6 +713,7 @@ set(APP_HEADERS

				    src/util/serial_job_lane.h

				    src/util/fetch_backoff.h

				    src/util/coalescing_writer.h

				    src/util/local_time.h

				    src/util/background_sampler.h

				    src/util/amount_format.h

				    src/util/base64.h