memory usage probs 2004-03-20 - By Matthew Hodgson
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Hi,
I 've been having problems with segfaults under mod_auth_mysql in Apache
1.3, which I think i 've narrowed down to the MYSQL connection structure
getting corrupted on my particular mysql installation - specifically
manifesting itself with strange values of the free_me field, which results
in the structure being incorrectly free 'd.
If anyone can confirm that the following shows something fundamentally
wrong with my mysql install i 'd appreciate it hugely:
box 130% cat test.c
#include <mysql/mysql.h >
int main() {
MYSQL *m;
m = mysql_init(0);
printf( "free_me is %d\n ", m- >free_me);
return 0;
}
box 131% gcc -g -L/usr/local/lib/mysql -lmysqlclient -lm -o foo test.c
box 132% ./foo
free_me is 0
This is using libmysqlclient.so.12.0.0 on a P4 Xeon running linux 2.4.22
with libc 2.3.1; mysql 4.0.17 built from source with:
./configure --prefix=/opt/mysql-4.0.17
--localstatedir=/usr/local/var/mysql --without-innodb --without-docs
--without-bench --with-mysqld-user=mysql
The code in libmysql.c appears to say:
mysql_init(MYSQL *mysql) {
if (!mysql) {
<malloc mysql >
mysql- >free_me=1;
}
...
}
so I 'm at a complete loss to explain why m- >free_me appears as 0 in the
above mini example.
Meanwhile, precisely the same program on a dual PIII machine running
Debian Woody, libmysqlclient 12.0.0 to match 4.0.16 yields:
deb 30% ./foo
free_me is 1
Superficially other operations seem to work - but segfaults ensue on
mysql_close(); and gdb reveals several fields of the connection structure
to change radically between simple operations. For instace running a
mysql_select_db() sets the value of free_me to 0x03, amongst others:
freshly inited mysql_handle, populated with some settings:
(gdb) print *mysql_handle
$1 = {net = {vio = 0x84efd30, fd = 139421480, fcntl = 139429672, buff = 0x84f6728 " ", buff_end = 0x84f6728 " ",
write_pos = 0x6 <Address 0x6 out of bounds >, read_pos = 0x2000 <Address 0x2000 out of bounds >,
last_error = "\0\0\0@\0\0\0\0\003\0\0\0\003\0\0\0\2003á\001\2003á\001\001 ", '\0 ' <repeats 174 times >, last_errno = 0, max_packet = 0,
timeout = 0, pkt_nr = 0, error = 0 '\0 ', return_errno = 0 '\0 ', compress = 0 '\0 ', no_send_ok = 0 '\0 ', remain_in_buf = 0, length = 0,
buf_length = 0, where_b = 0, return_status = 0x0, reading_or_writing = 0 '\0 ', save_char = 0 '\0 '}, connector_fd = 0x0, host = 0x0,
user = 0x0, passwd = 0x0, unix_socket = 0x0, server_version = 0x0, host_info = 0x84f01a0 "auth.domain.com ", info = 0x84f01e8 "auth ",
db = 0x84f01f8 "xxxxxxxx ", port = 0, client_flag = 139395520, server_capabilities = 139395456, protocol_version = 0, field_count = 0,
server_status = 1074172704, thread_id = 0, affected_rows = 0, insert_id = 0, extra_info = 0, packet_length = 0, status = MYSQL_STATUS_READY,
fields = 0x0, field_alloc = {free = 0x0, used = 0x0, pre_alloc = 0x0, min_malloc = 0, block_size = 0, error_handler = 0x2f43},
free_me = 0 '\0 ', reconnect = 0 '\0 ', options = {connect_timeout = 3306, client_flag = 8197, compress = 44 ', ', named_pipe = 0 '\0 ',
port = 10, host = 0x0, init_command = 0x2 <Address 0x2 out of bounds >, user = 0x8 <Address 0x8 out of bounds >, password = 0x0,
unix_socket = 0x0, db = 0x0, my_cnf_file = 0x0, my_cnf_group = 0x0, charset_dir = 0x0, charset_name = 0x0, use_ssl = 0 '\0 ',
ssl_key = 0x0, ssl_cert = 0x0, ssl_ca = 0x0, ssl_capath = 0x0}, scramble_buff = "\0\0\0\0\0\0\0\0 ", charset = 0x0, server_language = 0}
(gdb) step
506 if (mysql_select_db(mysql_handle,m- >mysqlDB) != 0) {
(gdb) print *mysql_handle
$2 = {net = {vio = 0x84efd30, fd = 139421480, fcntl = 139429672, buff = 0x84f6728 " ", buff_end = 0x84f6728 " ",
write_pos = 0x6 <Address 0x6 out of bounds >, read_pos = 0x2000 <Address 0x2000 out of bounds >,
last_error = "\0\0\0@\0\0\0\0\002\0\0\0\002\0\0\0\2003á\001\2003á\001\001 ", '\0 ' <repeats 174 times >, last_errno = 0, max_packet = 0,
timeout = 0, pkt_nr = 0, error = 0 '\0 ', return_errno = 0 '\0 ', compress = 0 '\0 ', no_send_ok = 0 '\0 ', remain_in_buf = 0, length = 0,
buf_length = 0, where_b = 0, return_status = 0x0, reading_or_writing = 0 '\0 ', save_char = 0 '\0 '}, connector_fd = 0x0, host = 0x0,
user = 0x0, passwd = 0x0, unix_socket = 0x0, server_version = 0x0, host_info = 0x84f01a0 "auth.domain.com ", info = 0x84f01e8 "auth ",
db = 0x84f01f8 "xxxxxxxx ", port = 0, client_flag = 139395520, server_capabilities = 139395456, protocol_version = 0,
field_count = 139395592, server_status = 1074172704, thread_id = 0, affected_rows = 0, insert_id = 0, extra_info = 0, packet_length = 0,
status = MYSQL_STATUS_READY, fields = 0xffffffff, field_alloc = {free = 0xffffffff, used = 0x0, pre_alloc = 0x0, min_malloc = 0,
block_size = 0, error_handler = 0x2f43}, free_me = 3 '\003 ', reconnect = 0 '\0 ', options = {connect_timeout = 3306, client_flag = 8197,
compress = 44 ', ', named_pipe = 0 '\0 ', port = 10, host = 0x0, init_command = 0x2 <Address 0x2 out of bounds >,
user = 0x8 <Address 0x8 out of bounds >, password = 0x0, unix_socket = 0x0, db = 0x0, my_cnf_file = 0x0, my_cnf_group = 0x0,
charset_dir = 0x0, charset_name = 0x0, use_ssl = 0 '\0 ', ssl_key = 0x0, ssl_cert = 0x0, ssl_ca = 0x0, ssl_capath = 0x0},
scramble_buff = "\0\0\0\0\0\0\0\0 ", charset = 0x0, server_language = 0}
Any ideas would be very much appreciated;
M.
--
matthew@(protected)
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