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From: Eric Blake <eblake@redhat.com>
Message-ID: <226818c6-e0d6-fc81-c473-98bcb656d3bd@redhat.com>
Date: Mon, 20 Aug 2018 13:38:55 -0500
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Subject: Re: [Qemu-devel] [PATCH v2 52/60] json: Eliminate lexer state
 IN_WHITESPACE, pseudo-token JSON_SKIP
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To: Markus Armbruster <armbru@redhat.com>
Cc: qemu-devel@nongnu.org, marcandre.lureau@redhat.com, mdroth@linux.vnet.ibm.com

On 08/20/2018 06:51 AM, Markus Armbruster wrote:

>> Hmm, if we did this:
>>
>> [IN_START_INTERPOL] {
>>    ['%'] = IN_INTERPOL,
>>    ['\t'] = IN_START_INTERPOL,
>> ...
>> }
>>
>> for similarity with all our other constructs, will gcc remember that
>> we've already initialized other members not listed in the clause
>> before, or will it mistakenly re-0-initialize the array members not
>> mentioned?
> 
> Fails make check.
> 
> (gdb) p json_lexer[IN_START_INTERPOL]
> $1 = "\000\000\000\000\000\000\000\000\000\016\016\000\000\016", '\000' <repeats 18 times>, "\016\000\000\000\000\035", '\000' <repeats 217 times>

And thus answered my question - abbreviating causes gcc to 
re-zero-initialize any unmentioned members, so your override has to be 
one member at a time, as originally written.

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