[tz] Timezone change detection

Guy Harris gharris at sonic.net
Sat Sep 4 08:36:02 UTC 2021

On Sep 3, 2021, at 6:11 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:

> A and B might have different values if tzdb is updated between the two calls to localtime_rz. Even though tz is a time zone "value", it is a "value" that mutates when tzdb is updated. This usage appears to be particularly problematic, as part of the point of localtime_rz is speed and thread-safety, and I'd hate for it to have to consult the filesystem.

As far as I know, the Darwin scheme does not bother checking for tzdb updates, it just handles explicit notifications that the system time zone has changed, so this would be a change over and above what you get in, for example, macOS.

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