Re: [Qemu-devel] [PATCH v2] qapi: Fix error handling code on alternate conflict

[Eric Blake <eblake@redhat.com>]

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On 07/17/2017 01:09 PM, Eduardo Habkost wrote:
> The conflict check added by commit c0644771 ("qapi: Reject
> alternates that can't work with keyval_parse()") doesn't work
> with the following declaration:
> 
>   { 'alternate': 'Alt',
>     'data': { 'one': 'bool',
>               'two': 'str' } }
> 
> It crashes with:
> 
>   Traceback (most recent call last):
>     File "./scripts/qapi-types.py", line 295, in <module>
>       schema = QAPISchema(input_file)
>     File "/home/ehabkost/rh/proj/virt/qemu/scripts/qapi.py", line 1468, in __init__
>       self.exprs = check_exprs(parser.exprs)
>     File "/home/ehabkost/rh/proj/virt/qemu/scripts/qapi.py", line 958, in check_exprs
>       check_alternate(expr, info)
>     File "/home/ehabkost/rh/proj/virt/qemu/scripts/qapi.py", line 830, in check_alternate
>       % (name, key, types_seen[qtype]))
>   KeyError: 'QTYPE_QSTRING'
> 
> This happens because the previously-seen conflicting member
> ('one') can't be found at types_seen[qtype], but at
> types_seen['QTYPE_BOOL'].
> 
> Fix the bug by moving the error check to the same loop that adds
> new items to types_seen, raising an exception if types_seen[qt]
> is already set.
> 
> Add two additional test cases that can detect the bug.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---

If this misses tomorrow's freeze deadline, it's borderline for inclusion
in 2.10 (it does not change the qemu binary proper, but rather fixes a
build tool crash, where the crash is only provoked by bad input and we
won't have any bad input at the time of the freeze) - I'll leave it up
to Markus on whether to take now or defer to 2.11.  But either way:

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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