Using regcomp/regexec in code - are POSIX extended regular expressions available all archs?

[Matt Grant]

Hi!

I am looking at using these functions in source3/utils/testparm.c to check
network/netmask and IP address for use with lib/util/access.c
allow_access() parameters for dynamic DNS filters for the SAMBA_INTERNAL
dns server.

Are the Linux POSIX extended regular expressions available on all compile
targets?  (*BSD, Linux, SVr4, AIX, IBM i) etc?

Been around Linux since the early nineties.  Things would be easier if
Samba supported libpcre2, the Regexps for samba-tool testparm are a slam
dunk as they are basically Perl regular expressions.

Want to know before cutting code and getting it into master.

Best Regards,

Matt Grant