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

[Rob Hoes <Rob.Hoes@xxxxxxxxxx>]

On 25 Jun 2015, at 16:59, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 
> 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.
> 

Fair enough, I thought Iâd just give it a go and see what happens. :)

My other option was to leave some gaps between error codes so that you can 
easily fit some in between in a logical order. Anyway, I am first going to 
focus on finding patterns and possible groupings of error codes without caring 
too much about the numbering.

Rob
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