tree d76356c1b62fa4a12f1a714dfba12bd0920097a8
parent f30094e2f4a01ea1e31c4efcccc397c212309c7e
author Maxim Dounin <mdounin@mdounin.ru> 1614618043 +0300
committer Maxim Dounin <mdounin@mdounin.ru> 1614618043 +0300

Improved maximum errno detection.

Previously, systems without sys_nerr (or _sys_nerr) were handled with an
assumption that errors start at 0 and continuous.  This is, however, not
something POSIX requires, and not true on some platforms.

Notably, on Linux, where sys_nerr is no longer available for newly linked
binaries starting with glibc 2.32, there are gaps in error list, which
used to stop us from properly detecting maximum errno.  Further, on
GNU/Hurd errors start at 0x40000001.

With this change, maximum errno detection is moved to the runtime code,
now able to ignore gaps, and also detects the first error if needed.
This fixes observed "Unknown error" messages as seen on Linux with
glibc 2.32 and on GNU/Hurd.