Re: [PATCH RFC 2/9] libxl idl: allow implicit enum values

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-06-24 at 16:08 +0100, Ian Jackson wrote:
> Rob Hoes writes ("[PATCH RFC 2/9] libxl idl: allow implicit enum values"):
> > Introducing two special enum values:
> > * ENUM_NEXT: equal to the previous value in the enum plus 1
> > * ENUM_PREV: equal to the previous value in the enum minus 1
> > 
> > This makes it a little easier to maintain enums for which we do not care too
> > much about the exact enum values.
> 
> It means that enum values can't be looked up without compiling the
> code.  It also means that deleting an old enum value would result in
> unexpected and undesirable changes to subsequent enums.
> 
> So I'm afraid I don't agree with this approach.

Neither do I.

An unstable ABI is one thing, having error messages change randomly from
"error -3" to "error -4" because someone added a new one is a step too
far though I think.