Compiling MariaDB for Debugging
Contents
Compiling MariaDB with full debug information includes all code symbols and also new code to do internal testing of structures and allow one to trace MariaDB execution. A full debug binary will be notably slower than a normal binary (30%).
Compiling MariaDB for Debugging Using the CMAKE_BUILD_TYPE Option
On Unix systems, you can build a debug build by executing cmake and by setting the CMAKE_BUILD_TYPE option to Debug. For example:
cmake -DCMAKE_BUILD_TYPE=Debug .
Compiling MariaDB for Debugging Using Build Scripts
The other option is to use the scripts in the BUILD directory that will compile MariaDB with most common debug options and plugins:
./BUILD/compile-pentium64-debug-max
or alternatively if you want to use the Valgrind memory checking tool with the MariaDB test system:
./BUILD/compile-pentium64-valgrind-max
There are separate build scripts for different configurations in the BUILD directory.
You can find a list of the needed packages/libraries for building on Linux here.
Example of Compiling MariaDB for Debugging Using Build Scripts
- Scripts containing "debug" in the name are for developers that want to build, develop and test MariaDB.
- Scripts containing "valgrind" in the name are for running mysqld under [[|http://valgrind.org|valgrind]]. Compiling for valgrind means that we are using another implementation of MEM_ROOT to allow valgrind to better detect memory overruns. In addition, some memory areas are marked as used/not used to remove some false positives.
- Scripts containing "max" in the name include all normal plugins.
Here 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 sql/mysqld.
If you have a system other than 64 bit Intel/AMD on Linux you can use a
different BUILD/...-debug-max file. If this fails, you can
try with:
cmake --build . --config Debug make -j4
Building Optimized Build With Debug Symbols
To build MariaDB with symbols, to get better stack traces and to be able to debug the binary with gdb, you need to supply the -g3 option to the gcc compiler.
Just compiling with -g3 will make the binary much bigger but the slowdown of the server should be negligible.
One way to do this is to edit the script
BUILD/compile-pentium64-max
and add the -g3 last on the line with extra_flags, like this:
extra_flags="$pentium64_cflags $fast_cflags -g3"
After that you can compile MariaDB with debugging symbols by just execution the above script.
Doing a Debug Build on Debian/Ubuntu
To build a "mysqld" binary with debugging enabled that uses the same parameters as the ones used in Debian/Ubuntu binary packages, you must do as follows (you must have a deb-src line of one of the MariaDB repositories on your /etc/apt/sources.list in order to do that):
apt-get build-dep mariadb-10.2 apt-get install cmake libaio1 libaio-dev apt-get source mariadb-10.2 cd mariadb-10.2* ./debian/rules configure ./BUILD/compile-pentuim64-debug-all
Then you will have your "debugging enabled" mysqld binary in the sql/ directory.
This binary can directly replace the one provided by the binary package that is placed on "/usr/bin/mysqld".
Temporarily Installing your Debug Build
The commands shown below replace the release mysqld binary with the debug mysqld binary that you compiled. Most importantly, they replace the binary in a way which makes it trivial to revert back to the
original release mysqld binary.
First, stop MariaDB.
Then, use the mv utility to rename the release mysqld binary:
sudo mv /usr/sbin/mysqld /usr/sbin/mysqld-orig
Note: Do not use the cp utility because that will change the file modification timestamp.
Then, install the debug mysqld binary from your source tree:
sudo install ~/mariadb-10.3.14/sql/mysqld /usr/sbin/mysqld-debug
Then, link the mysqld path to the path of your debug mysqld binary:
sudo ln -s /usr/sbin/mysqld-debug /usr/sbin/mysqld
Then, start MariaDB.
Be sure to replace /usr/sbin/mysqld with the path to your mysqld binary and to also replace ~/mariadb-10.3.14/sql/mysqldmysqld binary.
Reinstalling your Release Build
If you want to restore your original mysqld binary, you can do it with the following process::
First, stop MariaDB.
Then, execute the following command to delete the symbolic link:
sudo rm /usr/sbin/mysqld
Then, execute the following command to move the original mysqld release binary back into place:
sudo mv /usr/sbin/mysqld-orig /usr/sbin/mysqld
Then, start MariaDB.
Be sure to replace /usr/sbin/mysqld with the path to your mysqld binary
Notice that the debug mysqld binary located at /usr/sbin/mysqld-debug was not deleted. Only the symbolic link to this file was deleted. The debug mysqld binary is still present if it is needed again in the future.
Different Compilation Options
Changing DBUG_ASSERT to Print to Error Log
A debug binary has lots of code checks and asserts, that are not checked in production. This is done to get more performance when running in production. In some cases, when one is trying to find a hard-to-repeat bug, it could be beneficial to have these checks in production builds too.
Compiling with -DDBUG_ASSERT_AS_PRINTF will change DBUG_ASSERT() to print any failed check to the error log.
cmake . -DDBUG_ASSERT_AS_PRINTF
Enabling the above option should not have any notable impact on performance (probably < 1% slowdown). This is achieved by grouping asserts in MariaDB server code into two groups:
- Fast checks, using
DBUG_ASSERT(): These are converted to printing to error log. - Slow checks, using
DBUG_SLOW_ASSERT(). These will always be removed in production builds.
