Re: [Qemu-devel] [PATCH v2 for-2.5? 0/4] qjson: save a lot of memory

[Markus Armbruster]

Paolo Bonzini <address@hidden> writes:

> On 25/11/2015 15:47, Markus Armbruster wrote:
>> > This patch from 2011 (!) saves about 96% of the allocation cost (down
>> > from 500 MiB to 20 MiB) for check-qjson.
>> 
>> Looks good to me apart from the incomplete transition to recursive
>> descent in PATCH 2.
>
> I do not understand whether that is a problem.  Is the remark from the
> commit message incorrect ("Saving the parser context is mostly
> unnecessary; we can replace it with peeking at the next token, or remove
> it altogether when the restore only happens on errors.  The token list
> is destroyed anyway on errors.")?

The token sequence

    { 1 [ 2 ] }

gets parsed as [ 2 ].  See my reply to PATCH 2 for a more detailed
explanation.

I didn't bother to construct an example where QMP executes the incorrect
result, and I'm not sure it's possible.

Regardless, I'm fixing it, by simplifying the parser some more.