I have a program prototyped in PHP that works fine, but when I
convert it to C using libmysqlclient the program fails inside the
mysqlclient library with a segmentation fault on a particular query.
It fails on two different platforms (Linux and Mac OS X).
The database I'm using is very simple:
mysql> describe documents;
+-------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------+------+-----+---------+----------------+
| document_id | int(10) unsigned | | PRI | NULL | auto_increment |
| document | varchar(255) | | UNI | | |
+-------------+------------------+------+-----+---------+----------------+
mysql> describe words;
+---------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+------------------+------+-----+---------+----------------+
| word_id | int(10) unsigned | | PRI | NULL | auto_increment |
| word | varchar(255) | | UNI | | |
+---------+------------------+------+-----+---------+----------------+
mysql> describe main_index;
+-------------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+------------------+------+-----+---------+-------+
| document_id | int(10) unsigned | | PRI | 0 | |
| sequence | int(10) unsigned | | PRI | 0 | |
| word_id | int(10) unsigned | | MUL | 0 | |
+-------------+------------------+------+-----+---------+-------+
mysql> select distinct document from documents, main_index, words
where words.word="hello" and
documents.document_id=main_index.document_id and
main_index.word_id=words.word_id;
+----------+
| document |
+----------+
| market1 |
| market2 |
| market3 |
| market4 |
+----------+
If I build and run this same query in PHP it also works correctly but
when I do it using the C library it core dumps. Other simpler
queries do work correctly.
Using gdb, I get:
(gdb) r
Starting program: /home/bill/indexer/t.server
Program received signal SIGSEGV, Segmentation fault.
0x4002d26b in simple_command ()
from /usr/local/mysql/lib/mysql/libmysqlclient.so.10
(gdb) where
#0 0x4002d26b in simple_command ()
from /usr/local/mysql/lib/mysql/libmysqlclient.so.10
#1 0x4003021f in mysql_real_query ()
from /usr/local/mysql/lib/mysql/libmysqlclient.so.10
#2 0x400301be in mysql_query ()
from /usr/local/mysql/lib/mysql/libmysqlclient.so.10
#3 0x0804e846 in mydb_query (
query=0xbffff130 "select distinct document from documents,
main_index, words where words.word=\"hello\" and
documents.document_id=main_index.document_id and
main_index.word_id=words.word_id") at query.c:30
#4 0x0804e566 in search_start (word=0x807da87 "hello") at search.c:18
#5 0x0804e6fa in do_search (argc=3, argv=0x8051900) at search.c:72
#6 0x0804a9ca in interact () at server.c:745
#7 0x0804af84 in main (argc=1, argv=0xbffffacc) at server.c:903
#8 0x40060177 in __libc_start_main (main=0x804aa14 <main>, argc=1,
I tried calling mysql_real_query directly but that didn't fix anything.
Bill
--
Bill Rausch, Software Development, UNIX, Mac, Windows
Numerical Applications, Richland, WA 509-943-0861
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