Hi everybody!
I'm having big problems with crashes in programs that use MySQL++. They seem
to crash somewhere in Query::store(), but not on every call. It can be on the
second call to store(), or the fifth. Some programs don't crash at all, and
those that do seem to crash in the same place every time as long as the
environment doesn't change too much.
The crashes started happening when I upgraded from Fedora Core 3 to Fedora
Core 4, so there are new versions of just about everything in the system. I
also run these programs on Suse 9.2, and so far they don't crash there. One
might then think the bug is in GCC or some system library in Fedora 4, but no
other programs are crashing, only these that use MySQL++. I'd rather think
it's some change that has exposed a previously hidden bug.
I have tried MySQL++ 1.7.35, 1.7.40 and 2.0.0-rc1. (I compile MySQL++
locally.) I've also tried replacing MySQL 4.1.12 from Fedora with a locally
compiled MySQL 4.0.25. These changes didn't help. They only caused the
crashes to happen in other places.
So it seems that either I'm doing something wrong, or it's a bug in MySQL++. I
thought I had figured out a way I could use the library without causing
dangling pointers and such, but maybe I was wrong. I don't think I can
produce a test case that crashes reproducibly, but here's a stripped-down
example of how I use the library:
I establish a connection and pass the connection object to a function (called
"worker" here). When this function returns I close the connection:
Connection con(use_exceptions);
string DB_username;
try {
DB_username = "ess_user";
con.real_connect("ess", NULL, DB_username.c_str(), "password");
worker(con);
con.close();
}
catch (exception& error) {
cerr << "Error: " << error.what() << endl;
}
In this other function, I write queries into Query objects and execute them
with store(). If I know that the query only returns one line I store the
first like in a Row object. Otherwise I typically iterate over the result
with a Result::iterator:
void worker(Connection& con) {
Query data_query = con.query();
Query product_query = con.query();
Query company_query = con.query();
Result data_result;
Result product_result;
Result company_result;
Row data;
data_query << "select company, contact, sum "
"from " << table_name
<< " where ID=" << reference;
data_result = data_query.store();
if(data_result.num_rows() < 1) {
throw not_found("Ogiltig referens.");
}
data = data_result[0];
company_ID = string(data.lookup_by_name("company"));
product_query << "select ID, name from products, product_privileges "
"where ID=product and user=" << user.ID;
product_result = product_query.store();
for(Result::iterator rowp = product_result.begin();
rowp != product_result.end();
rowp++)
{
do_stuff_with(string((*rowp)[0]), string((*rowp)[1]));
}
company_query << "select name from companies where ID=" << company_ID;
company_result = company_query.store();
if(company_result.num_rows() < 1) {
throw not_found("Obefintligt företag.");
}
And on one of the calls to store(): bang! Is there anything in this code that
can cause that?
Is anyone else having this problem? Are there any other users of Fedora 4 on
this list?
I also sometimes get error printouts from GlibC about corrupted pointers. I'm
not sure how related they are to the crash problem, as programs sometimes run
to completion after these printouts. Here are some examples. I have memory
maps too if anyone wants them.
*** glibc detected *** /home/bjorn/jobb/säljstöd/ess/show_company: corrupted
double-linked list: 0x084c0190 ***
======= Backtrace: =========
/lib/libc.so.6[0x76e548]
/lib/libc.so.6(__libc_free+0x77)[0x76e95f]
/usr/lib/mysql/libmysqlclient.so.14(my_no_flags_free+0x21)[0x1b4fb2]
/usr/lib/mysql/libmysqlclient.so.14(mysql_free_result+0x72)[0x1d386d]
/usr/local/lib/libmysqlpp.so.4(_ZN7mysqlpp6ResUse5purgeEv+0x28)[0x3167b4]
/usr/local/lib/libmysqlpp.so.4(_ZN7mysqlpp6ResUseD2Ev+0x2e)[0x316342]
/home/bjorn/jobb/säljstöd/ess/show_company(_ZN7mysqlpp6ResultD1Ev+0x21)
[0x8050793]
/home/bjorn/jobb/säljstöd/ess/show_company[0x804f8ec]
/home/bjorn/jobb/säljstöd/ess/show_company[0x805ada5]
/home/bjorn/jobb/säljstöd/ess/show_company(__gxx_personality_v0+0x18e)
[0x804d0d6]
/lib/libc.so.6(__libc_start_main+0xc6)[0x71fde6]
/home/bjorn/jobb/säljstöd/ess/show_company(__gxx_personality_v0+0x91)
[0x804cfd9]
*** glibc detected
*** /home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/show_tender: double
free or corruption (!prev): 0x09030190 ***
======= Backtrace: =========
/lib/libc.so.6[0x870424]
/lib/libc.so.6(__libc_free+0x77)[0x87095f]
/usr/local/lib/libmysqlpp.so.2(my_no_flags_free+0x16)[0x78bb86]
/usr/local/lib/libmysqlpp.so.2(mysql_close+0x61)[0x789d25]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/show_tender[0x8056af9]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/show_tender[0x8055ba1]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/show_tender(__gxx_personality_v0+0x19e)
[0x804c1be]
/lib/libc.so.6(__libc_start_main+0xc6)[0x821de6]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/show_tender(__gxx_personality_v0+0xa1)
[0x804c0c1]
*** glibc detected
*** /home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/enter_event: free():
invalid pointer: 0x08411610 ***
======= Backtrace: =========
/lib/libc.so.6[0x92f424]
/lib/libc.so.6(__libc_free+0x77)[0x92f95f]
/usr/lib/libstdc++.so.6(_ZdlPv+0x21)[0x7563a9]
/usr/local/lib/libmysqlpp.so.2
(_ZN9__gnu_cxx10__mt_allocIN7mysqlpp15mysql_type_infoENS_20__common_pool_policyINS_6__poolELb1EEEE10deallocateEPS2_j+0x46)
[0x1f3aca]
/usr/local/lib/libmysqlpp.so.2(_ZN7mysqlpp6ResUse5purgeEv+0xd5)[0x1fd745]
/usr/local/lib/libmysqlpp.so.2(_ZN7mysqlpp6ResUseD2Ev+0x43)[0x1fd077]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/enter_event(_ZN7mysqlpp6ResultD1Ev+0x3b)
[0x805397f]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/enter_event[0x8051eb1]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/enter_event[0x805c497]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/enter_event(__gxx_personality_v0+0x280)
[0x804c388]
/lib/libc.so.6(__libc_start_main+0xc6)[0x8e0de6]
/home/bjorn/jobb/säljstöd/ess-X/branches/MySQL++2/enter_event(__gxx_personality_v0+0xa1)
[0x804c1a9]
Björn Persson
