Debugging MariaDB With a Debugger
- Checking That MariaDB is Compiled For Debugging
- Building MariaDB for Debugging Starting from 5.5
- Building MariaDB 5.3 and Older
- Debugging MariaDB From the Source Directory
- Debugging MariaDB Server with mysql-test-run
- See Also
If you have MariaDB compiled for debugging you can both use it in a debugger, like ddd or gdb, and get comprehensive trace files of the execution of MariaDB. The trace files allow you to both see the flow of the code and to see the differences in execution by by comparing two trace files.
Core dumps are also much easier to investigate if they come from a debug binary.
Note that a binary compiled for debugging and tracing is about 10-20% slower than a normal binary. If you just compile a binary for debugging (option
-g with gcc) the speed difference compared to a normal binary is negligible.
Checking That MariaDB is Compiled For Debugging
mysqld --debug --help
If you get an error
unknown option '--debug, then MariaDB is not compiled
for debugging and tracing.
Building MariaDB for Debugging Starting from 5.5
On Unix you need to pass
-DCMAKE_BUILD_TYPE=Debug to cmake to compile with debug information.
Building MariaDB 5.3 and Older
Here is how you compile with debug on older versions:
Use the scripts in the BUILD directory that will compile MariaDB with most common debug options and plugins, for example:
For the most common configurations there exists a fine-tuned script in the BUILD directory.
If you want to use valgrind, a very good memory instrumentation tool and memory overrun checker, you should use
Some recommended debugging scripts for Intel/AMD are:
This is an example of how to compile MariaDB for debugging in your home directory with MariaDB 5.2.9 as an example:
cd ~ mkdir mariadb cd mariadb tar xvf mariadb-5.2.9.tar.gz ln -s mariadb-5.2.9 current cd current ./BUILD/compile-pentium64-debug-max
The last command will produce a debug version of
Debugging MariaDB From the Source Directory
Creating the MariaDB Database Directory
The following example creates the MariaDB databases in
./scripts/mysql_install_db --srcdir=. --datadir=/data
Running MariaDB in a Debugger
The following example is using
ddd, an excellent graphical debugger in Linux. If you don't have
ddd installed, you can use
cd sql ddd ./mysqld &
run --datadir=/data --language=./share/english --gdb
You can set the options in your /.my.cnf file so as not to have to repeat them on the
If you run
--debug, you will get a trace file in /tmp/mysqld.trace that shows what is happening.
Note that you can have different options in the configuration file for each MariaDB version (like having a specific language directory).
Debugging MariaDB Server with mysql-test-run
If you get a crash while running
mysql-test-run you can debug this in a debugger by using one of the following options:
mysql-test-run --gdb failing-test-name
or if you prefer the
mysql-test-run --ddd failing-test-name
Sample .my.cnf file to Make Debugging Easier
[client-server] socket=/tmp/mysql-dbug.sock port=3307 [mariadb] datadir=/my/data loose-innodb_file_per_table server_id= 1 log-basename=master loose-debug-mutex-deadlock-detector max-connections=20 lc-messages=en_us [mariadb-10.0] lc-messages-dir=/my/maria-10.0/sql/share [mariadb-10.1] lc-messages-dir=/my/maria-10.1/sql/share [mariadb-10.2] lc-messages-dir=/my/maria-10.2/sql/share [mariadb-10.3] lc-messages-dir=/my/maria-10.3/sql/share
- Uses an explicit socket for both client and server.
- Assumes the server source is in /my/maria-xxx. You should change this to point to where your sources are located.
- Has a unique patch for each MariaDB version so that one doesn't have to specify --lc-messages-dir or --language even if one switches between debugging different MariaDB versions.