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

[Eduardo Habkost]

On Mon, Jul 17, 2017 at 09:45:01AM -0500, Eric Blake wrote:
> On 07/14/2017 03:33 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 <address@hidden>
> > ---
> 
> > +++ b/tests/qapi-schema/alternate-conflict-bool-string.err
> > @@ -0,0 +1 @@
> > +tests/qapi-schema/alternate-conflict-bool-string.json:3: Alternate 'Alt' 
> > member 'two' can't be distinguished from member 'one'
> 
> Claims the error is at line 3,
> 
> > +++ b/tests/qapi-schema/alternate-conflict-bool-string.json
> > @@ -0,0 +1,4 @@
> > +# alternate branches of 'str' type conflict with all scalar types
> > +{ 'alternate': 'Alt',
> 
> but the declaration starts at line 2.  That's probably why patchew
> complained that your patch doesn't build.  The idea looks sane, though;
> looking forward to v2.

Oops, sorry!  I had a two-line comment in the beginning of the
file and decided to update it just before submitting the series.

-- 
Eduardo