[lwip-users] ENSR* error codes (errno) in DNS code

[Mason]

Hello everyone,

The file src/include/lwip/arch.h defines several error codes,
some of which are used in DNS-related operations: the ENSR*
error codes such as ENSRNOTFOUND.

sys_arch.txt states:

  [cc.h] must either include a system-local <errno.h> which defines
  the standard *nix error codes, or it should #define LWIP_PROVIDE_ERRNO
  to make lwip/arch.h define the codes which are used throughout.

I'm using my platform's errno header, so I've included <errno.h>
and I haven't defined LWIP_PROVIDE_ERRNO. It turns out that all
the ENSR* error codes are undefined on my platform.

The ENSR* error codes do not appear to be defined by POSIX.

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html

Are they standard? (which standard?) Or are they some kind
of extension?

If they are not POSIX, shouldn't they ALWAYS be provided,
whether LWIP_PROVIDE_ERRNO is defined or not?

Should I just copy the definitions to my cc.h file?

Are the values set in stone or are they likely to change
in the future?

What if some of the values clash with other values from
my platform's errno?

-- 
Regards.