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Re: [gpsd-dev] Tricky bug in the json parser


From: Christian Gagneraud
Subject: Re: [gpsd-dev] Tricky bug in the json parser
Date: Wed, 20 Jun 2012 10:45:50 +0100
User-agent: Mozilla/5.0 (X11; Linux i686; rv:12.0) Gecko/20120421 Thunderbird/12.0

On 20/06/12 01:52, Eric S. Raymond wrote:
Christian Gagneraud<address@hidden>:
Hi all,

I just have one last bug to fix from my live test campaign. and it
is a bit tricky to understand for me as I have to dive into the
hairy json.c.

So basically, here are 2 AIS sentences which contain an array of 1 struct:
!AIVDM,1,1,,A,address@hidden,0*02
!AIVDM,1,1,,A,6h2E3N0rThqP0600J00000000000,0*51

The dumping doesn't seems to cause any trouble, but reading back the
JSON crashes gpsdecode:
echo '!AIVDM,1,1,,A,address@hidden,0*02' | gpsdecode -ju
{"class":"AIS","device":"stdin","type":6,"repeat":3,"mmsi":2442101,"scaled":false,"seqno":2,"dest_mmsi":246351000,"retransmit":false,"dac":1,"fid":32,"month":0,"day":0,"tidals":[{"lon":-16777216,"lat":0,"from_hour":0,"from_min":0,"to_hour":0,"to_min":0,"cdir":0,"cspeed":0}]}
echo '!AIVDM,1,1,,A,address@hidden,0*02' | gpsdecode
-ju | gpsdecode -jeu
Segmentation fault

I saw some other messages with arrays of 0 structures, they don't
crash the json parser.

I'm getting back to GPSD after spending a week and a half immersed in
another project.  Did this one get fixed?

Yes, it is in my local branch. The needed changes are part of a big patch that fixes all the issues found in the AIS code. I didn't try to split that patch, because there are really plenty of small changes all around the place (touching only AIS code).

Chris

--
Christian Gagneraud,
Embedded systems engineer.
Techworks Marine
1 Harbour road
Dun Laoghaire
Co. Dublin
Ireland
Tel: + 353 (0) 1 236 5990
Web: http://www.techworks.ie/



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