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Cleaning up #includes

Cleaning up includes In previous article I described why you should care about clean #includes and what rules I suggest to achieve it. If you already have a project that doesn't follow those rules, it would be tedious manual task to implement my advises. This article describes how some tools can help you answer these questions:
How to replace include guards with pragma once in whole project?How to sort includes in whole project?How to remove redundant includes and add missing ones?How to replace angle bracket includes with quotes only for project headers? #pragma once with include-guard-convert.pyInclude-guard-convert is simple tool that will find all include guards and change them to #pragma once. Tool doesn't need installation, simply download script from github and run it on your header files:
wget chmod +x ./ proj_path/**/*.…
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Tidy #includes

Tidy #includes Having tidy includes in C++ project is often thought as low priority. It can however help you with making your code less fragile. This is doubly important when your project is a library that will be used by other people.
I propose that "good" includes should follow those rules:
Associated header (foo.hpp for foo.cpp) always comes firstAny file should have all the headers it needs. System headers are in <angle_brackets>, project headers are in "quotes"Project headers are first, STL headers are last, between them are libraries in order of decreasing locality.Use #pagma once instead of include guards Within groups decided by 4), alphabetic order is nice to have.  Associated header is first The header that declares class / methods should be the first to include. It also should have the same file name as current source file, except for extension. Some tools depend on this - for example IDEs use this to implement "go to declaration/implementatio…

Sending Firebase Messages from command line with curl

Google Firebase platform is set of services aimed at "cloudyfying" Android apps. One of those services is FCM, Firebase Cloud Messaging, and allows us to send short text or data messages to device or group of them.
Majority of tutorials show how to send this message from another Android device. This one will show how to send it from custom server, for simplicity using curl program. 
Steps needed:
Set up project in Firebase consoleCompile example app for this projectVerify sending works with web uiSend message using curl Set up project in Firebase consoleGo to Add projectEnter project name and click CreateOn the left menu select Grow / NotificationClick Android icon Enter package name. For this tutorial enter Register App, then Download google-services.json and save the fileFollow rest of instructions on website or in this tutorial Compile example appCheck out project firebase/quickstart-android

<chrono> introduction

This article will summarize presentation by Howard Hinnant which he gave during CppCon 2016. Howard gives comprehensive walk through c++11 chrono library.

TL;DR (Summary) C++11 introduced <chrono> library for handling time. Use it instead of <time.h> / <ctime> because it gives you better type safety and precision.
Library provides those concepts:
time points - moments in time (as in "noon, December 1st 2000", "2016-01-31 14:15:32")time durations - "length" (amount) of time that passes between two time points ("two hours", "2563 milliseconds")clocks - providers of time points (like wall clock, stopper) Query clock to get time points; calculate difference between two time points to get time duration. You can use time points/duration with <thread> library for sleep, wait_for/wait_until functions.
Use auto, because otherwise type names are quite verbose.
Time Durationstd::time_duration is a measure of how much time…

GDB - beyond basics

GDB is console debugger that every Linux-using programmer heard about. It is not however easy to learn. Greg Law in his CppCon talk presented some of obscure, but useful features.

Text user interface Normally we use GDB with command line interface (CI). Beyond this, GDB has TUI based on Curses library. To activate it, use keyboard shortcut ctrl-x-a (hold ctrl, press x, unpress x, press a). Now you can see the code as you go through it.
ctrl-x-a - activate/deactivate TUIctrl-l - when screen gets messed up, use it to redraw. Happens when program prints to stdout/stderrctrl-p / ctrl-n - since you can't use arrows to reuse previously written command, use ctr-p/n instead of arrow up/down
ctrl-f / ctrl-n are arrows left / right
ctrl-a / ctrl-e are home / end (all those are copied from Emacs)ctrl-x-2 - second window (assembly). Shell You can run shell commands inside GDB command line. Just use keyword "shell" at the beginning. Examples:
shell psshell cat temporary_file.txtshell k…

C++11 random - introduction

C++11 introduced robust random numbers library, <random>. Its author does great introduction in the video from Cppcon:
I will attempt to create short tutorial/HOWTO for this library.
Bad, old times Before C++11, when you wanted to get random numbers in range {1, 2, ... 10}, you wrote something like this:
#include <stdio.h>      /* printf, NULL */ #include <stdlib.h>     /* srand, rand */ #include <time.h>       /* time */ int main () { srand (time(NULL)); int num1 = rand()%10 + 1; int num2 = rand()%10 + 1; return 0; } Several things are wrong here:
It always gives uniform distribution (1 is as probable as 5). This is usually fine, but when not, you need a lot of additional work.Actually, it is not very uniform.If you want for some reason to reseed the generator (call srand(time(NULL)) again) shortly after first seeding, you may get repeated answersYou only get discreet numbers (integers)Random algorithm is not specified, so results are not portab…