Ad Astra Per Aspera – Software, science and random thoughts about IT

Malloc Internals

The Red Hat Developers Blog recently published this article about malloc internals which might be pretty interesting to those working with C.

The MQTT (Message Queue Telemetry Transport) messaging protocol is a lightweight protocol well suited for the Internet of Things. It is a simple protocol and an ISO standard. It comes with an extensible reference documentation.

To help me learn about it and simplify my work flow, I created this cheat sheet (warning: PDF) which highlights the most relevant details about the protocol. You can also see it online here.

Messaging performance: tips, tricks and tools

Today I gave a talk entitled “Messaging Performance: tips, tricks and tools” at the DevConf.cz 2017 in Brno. For those interested in the subject, I have made the slides available here.

The talk itself should also be available soon on the DevConf.cz channel on youtube.

Otavio’s must-watch linux.conf.au talks

I compiled a list of 8 talks from linux.conf.au 2017 that interested me. You can watch it here or just click play on the embedded video below:

EOY 2016 links

Some links about interesting things I’ve read or watched by the end of 2016. Further comments are provided on each item of the list.

Single file libraries: open source libraries with minimal dependencies.
The sorry state of programming world as the end of 2016 AD: food for though regarding how most of development is done nowadays.
Find my Phone: what happens when your phone is stolen.
PayPal Cuts Costs 10x With Open Source CI: self descriptive.
Learning to Read x86 Assembly: self descriptive.
Json-c tutorial: how to manipulate json in C.
The 101 of ELF Binaries on Linux: Understanding and Analysis: self descriptive.
How the Linux kernel knows it’s running in a Virtual Machine: self descriptive.
Stack Overflow: The Architecture – 2016 Edition: self descriptive.
AMQP 1.0 in Azure Service Bus and Event Hubs protocol guide: a detailed explanation abou AMQP 1.0.
10 Tips for C and C++ Performance Improvement Code Optimization: simple optimization tips.
Light Weight Protocol: Critical Implications: a talk about MQTT and security.
Modern C: a book about modern C programming.

Google Sanitizers and Fedora 25

Here’s a tip if you are using Fedora and trying to use one of the Google Sanitizers with clang and is having problems doing so. One of the common problems is not being able to find libclang_rt.asan-x86_64.a:

/usr/bin/ld: cannot find /usr/bin/../lib64/clang/3.8.0/lib/linux/libclang_rt.asan-x86_64.a: No such file or directory

1	/usr/bin/ld: cannot find /usr/bin/../lib64/clang/3.8.0/lib/linux/libclang_rt.asan-x86_64.a: No such file or directory

This can be resolved by simply installing the compiler-rt package:

dnf install -y compiler-rt

1	dnf install -y compiler-rt

Restoring click method behavior on Fedora 25 and libinput

Here’s a quick tip if you need to enable the Software Button Area behavior on an Apple macbook running Fedora 25:

xinput set-prop bcm5974 "libinput Click Method Enabled" 1 0

1	xinput set-prop bcm5974 "libinput Click Method Enabled" 1 0

Some comments about this:

You have to run it after every reboot
There’s, probably, a better way to do this. Per documentation, it should be possible to set it up permanently by creating a file on /etc/X11/xorg.conf.d however I did not manage to create a file that works so far.

References:

Libinput documentation: Clickpad Software Buttons
Libinput FAQ
Libinput Man Page

SonarQube 5.6 upgrade

Overall tips for upgrade a SonarQube instance from 5.4 to 5.6 LTS.

If you are using MariaDB as your database, please make sure to read the post SonarQube database migration: MariaDB 5.5 to MySQL 5.7.
Ignore the upgrade steps provided by the application. They are incomplete. If you execute them, the upgrade will finish with success but no rules will be enabled after that. Instead, execute the steps provided in this StackOverflow comment.
If you are using C++ community plugin, make sure that you are using at least version 0.9.6.
Ensure that you have Java 8.

SonarQube database migration: MariaDB 5.5 to MySQL 5.7

Newer versions of SonarQube have stopped supporting MariaDB and you may need to switch to MySQL instead. While I’d rather use MariaDB, I understand that it is not within the supported matrix. Therefore I am documenting the steps here. The steps are focused on RHEL 7 (they probably would work on Centos 7 as well, but I did not test it).

Before start with this process, shutdown your SonarQube instance as well as any other analysis that may access the database.

The first step is to use mysqldump to create a backup of your MariaDB database:

mysqldump sonar > sonar.sql

1	mysqldump sonar > sonar.sql

After the backup is complete, shutdown and disable your MariaDB instance:

systemctl stop mariadb ; systemctl disable mariadb

1	systemctl stop mariadb ; systemctl disable mariadb

Then install MySQL 5.7 from Software Collections. The process is documented on this page. These steps are for 5.6, however, you can just replace 56 with 57 in all the steps and the result is the same.

With the new MySQL 5.7 installed and running, create the database:

mysql -u root

1	mysql -u root

In the MySQL sheel recreate the database with the same credentials and permissions as the old one:

CREATE USER '[old username]'@'localhost' IDENTIFIED BY '[old password]';
GRANT ALL PRIVILEGES ON *.* TO '[old username]'@'localhost' WITH GRANT OPTION;
CREATE USER '[old username]'@'%' IDENTIFIED BY '[old password]';
GRANT ALL PRIVILEGES ON *.* TO '[old username]'@'%' WITH GRANT OPTION;

CREATE USER '[old username]'@'localhost' IDENTIFIED BY '[old password]';

GRANT ALL PRIVILEGES ON *.* TO '[old username]'@'localhost' WITH GRANT OPTION;

CREATE USER '[old username]'@'%' IDENTIFIED BY '[old password]';

GRANT ALL PRIVILEGES ON *.* TO '[old username]'@'%' WITH GRANT OPTION;

Then you can recover the backup into the new MySQL 5.7 instance:

mysqldump sonar < sonar.sql

1	mysqldump sonar < sonar.sql

Now you can go to your SonarQube server and start it.

Colors in GDB

I have been on a intense session of C/C++ hacking lately and one of the things I came across is this interesting StackOverflow topic about how to colorize the GDB output. There are plenty of tips there, but since I prefer vanilla GDB, I just stick to the first one and downloaded a customized GDB for myself.