Il 31/05/2012 16:31, Luiz Capitulino ha scritto:
>>>> Errors are not QAPI-ized yet, so we can add errno values to the above
>>>> five errors too.
>>>
>>> We've preferred adding new errors instead of adding errno values to
>>> existing errors. I don't remember exactly why, but I personally don't care.
>>
>> Then let's not do it anymore. :)
>
> We already did, changing this now will probably be worse.
Wait, I think you're conflating two things.
One is "do not shoehorn errors into errno values". So for QOM invalid values we
have PropertyValueBad, not a generic InvalidArgument value. We convert
everything
to Error rather than returning negative errno values and then returning generic
error codes, because those would be ugly and non-descriptive. I agree with
that.
The other is "when errors come straight from the OS, _do_ use errno values".
This is for OpenFileFailed, for the new socket errors and so on. This is what
I am proposing.
These two rules together match what most other programs do.
For example:
$ sed UUUU
sed: -e expression #1, char 1: unknown command: `U'
^^^^^^^^^^^^^^^^ error type
^^^^^^^^^^^^^ ^ ^ ^^^ arguments
in JSON:
{ 'error': 'UnknownCommand',
'source' : { 'type': 'expression',
'data': { 'number': 1, 'char': 1 } },
'command': 'U'
}
It does not say
sed: parsing program: No such system call
(aka ENOSYS). So far that's obvious. :) Now let's look at the second part, OS
errors:
$ echo | sed p > /dev/full
sed: couldn't flush stdout: No space left on device
^^^^^^^^^^^^^^ error type
^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^ arguments
That would become, in JSON:
{ 'error': 'FlushFailed',
'file': 'stdout',
'os_error': 'enospc' }
Here is similar example:
$ yes | sed p > /dev/full
sed: couldn't write 1 item to stdout: No space left on device
^^^^^^^^^^^^^^ error type
^ ^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^ arguments
{ 'error': 'WriteFailed',
'file': 'stdout', 'count': 1,
'os_error': 'enospc' }
Note how restricting everything to a single NoSpaceLeftOnDevice error would
force you to drop information such as filename or count.
Is it clearer?
Paolo
