The current implementation exits syslog_write_foreach function
if write to one channel fails, causing other channels not being written
and returning negated errno. libc syslog functions then stay in
an infinite loop, because error is returned and the same bytes
are still passed to syslograwstream_flush and syslog_write_foreach.
The channel write may fail for many reasons - disconnected USB if
CDC ACM syslog is enabled, lost networking if telnet syslog is enabled,
error on NOR flash etc. This shouldn't lead to an ininite loop in the
code though.
The solution ensures all channels in syslog_write_foreach are tried,
therefore the user get the output to the working channels even if
the first one is broken. It also updates syslograwstream_addchar and
syslograwstream_addstring to skip the bytes if all channels fails. This
ensures syslog call won't result in an infinite loop, but the user may
lost the debugging output.
Co-authored-by: Martin Krasula <mkrasula@elektroline.cz>
Signed-off-by: Michal Lenc <michallenc@seznam.cz>
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