[redland-dev] Redland MySQL double free()

[Christopher Schmidt]

Recently, something in my configuration seems to have changed, which 
means it is now impossible for me to run RDQL queries with two AND 
clauses.

An example crashing query is:

select ?prop, ?addr where (?who ?n "crschmidt") (?who ?prop ?addr)  
and ?n == foaf:name and ?prop == foaf:yahooChatID  
using foaf for <http://xmlns.com/foaf/0.1/>

The crash occurs after printing all the results from the query. Once it 
does, the useful portion of the backtrace, obtained from gdb, gives:

#0  0x401c6271 in kill () from /lib/libc.so.6
#1  0x40129131 in pthread_kill () from /lib/libpthread.so.0
#2  0x401294ab in raise () from /lib/libpthread.so.0
#3  0x401c6004 in raise () from /lib/libc.so.6
#4  0x401c74cd in abort () from /lib/libc.so.6
#5  0x40201d50 in mallopt () from /lib/libc.so.6
#6  0x402009c9 in mallopt () from /lib/libc.so.6
#7  0x401ff6bf in free () from /lib/libc.so.6
#8  0x406c91d2 in my_no_flags_free () from /usr/lib/libmysqlclient.so.12
#9  0x406c35ba in mysql_free_result () from 
/usr/lib/libmysqlclient.so.12
#10 0x4035b167 in 
librdf_storage_mysql_find_statements_in_context_finished 
(context=0x80bbd08) at rdf_storage_mysql.c:1736
#11 0x4034f87c in librdf_free_stream (stream=0x80bc208) at 
rdf_stream.c:118
#12 0x40352c37 in rasqal_redland_finish_triples_match (rtm=0x0, 
user_data=0x80bbff0) at rdf_query_rasqal.c:399
#13 0x407482b6 in rasqal_free_triples_match (rtm=0x80a6870) at 
rasqal_engine.c:376
#14 0x407485e4 in rasqal_engine_get_next_result (query=0x80b4320) at 
rasqal_engine.c:525
#15 0x40747868 in rasqal_query_results_next (query_results=0x4012eff4) 
at rasqal_query.c:732
#16 0x40352ea4 in librdf_query_rasqal_results_next (query_results=0x0) 
at rdf_query_rasqal.c:523
#17 0x40351cc0 in librdf_query_results_next (query_results=0x4012eff4) 
at rdf_query_results.c:99
#18 0x400275bf in _wrap_librdf_query_results_next (self=0x0, args=0x0) 
at Redland_wrap.c:2769

(Anything before that in the stack is just general Python calls; this is 
from the Python bindings.)

I am using the MySQL backend.

I'm not sure if this crash may be due to too much data being returned; 
so far as I'm aware, the only thing that has changed would be adding 
more triples to the returned results. 

The error given is:

*** glibc detected *** double free or corruption (fasttop): 0x080bbc90 ***

This is occuring with Redland version 0.9.18, mysql  Ver 12.22 
Distrib 4.0.21, for pc-linux-gnu (i686) on a gentoo system with 
ebuild-buit MySQL server and hand-built Redland.

This error occurs regardless of the number of returned triples. (The 
example query returns none.)

If there's anything I can do to provie more useful debug information, 
please let me know; I'm a complete novice when dealing with these kinds 
of errors.

-- 
Christopher Schmidt
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