In case anyone else encounters this particular symptom, it turns out the
problem was gcc using some orphaned headers for mysql 3.23.56 sitting in
/usr/include/mysql rather than the correct mysql 4.0.17 ones residing in
/usr/local/include/mysql, thus yielding all the strange behaviour.
M.
On Sat, 20 Mar 2004, Matthew Hodgson wrote:
> 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 = "[EMAIL PROTECTED]", '\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 = "[EMAIL PROTECTED]", '\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.
>
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