Debugging MariaDB With a Debugger

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 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

Execute:

If you are using MariaDB before 10.5, then you should use mysqld instead of mariadbd!

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 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 , 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 as an example:

The last command will produce a debug version of sql/mysqld.

Debugging MariaDB From the Source Directory

Creating the MariaDB Database Directory

The following example creates the MariaDB databases in /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 gdb instead.

In ddd or gdb

You can so as not to have to repeat them on the run line.

If you run mysqld with --debug, you will get a 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 mariadb-test-run

If you get a crash while running mariadb-test-run you can debug this in a debugger by using one of the following options:

or if you prefer the ddd debugger:

Sample .my.cnf file to Make Debugging Easier

The above .my.cnf file:

• 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 or even if one switches between debugging different MariaDB versions.

See Also

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