Starting from C++14:
#include <string>
#include <memory>
int main()
{
std::unique_ptr<std::string> p = std::make_unique<std::string>("abc");
auto func = [p = std::move(p)]()
{
};
func();
return 0;
}
Author Archives: dmitriano
The right way to capture std::unique_ptr into a lambda expression
MSVC 2022 compiler bug
Static asserts in the code below do not fail with MSVC 19.32.31332 for x86:
#include <string>
int main()
{
std::string v = "abc";
auto func = [v]()
{
auto& l_ref = v;
static_assert(std::is_same_v<decltype(l_ref), std::string&>);
auto&& r_ref = std::move(v);
static_assert(std::is_same_v<decltype(r_ref), std::string&&>);
};
func();
return 0;
}
that is MSVC compiler bug. With GCC both l_ref and r_ref are const references.
Thanks to stackoverflow.com.
(more…)Switching to PHP 7.4 on Ubuntu 16.04
Some WordPress plugins stopped working with PHP 7.0 on my Ubuntu 16.04 server and I switched to PHP 7.4 with the following commands:
sudo add-apt-repository ppa:jczaplicki/xenial-php74-temp
sudo apt-get update
sudo apt-get install php7.4 php7.4-fpm php7.4-cli php7.4-mysql php7.4-dom php7.4-mbstring -y
service php7.4-fpm status
cd /etc/php/7.4/fpm/pool.d
sudo mv www.conf www.conf.dist
sudo mv ../../../7.0/fpm/pool.d/devnote.conf .
sudo service php7.0-fpm reload
sudo service php7.4-fpm reload
An example of how r-value reference works in C++
An example of extending the lifetime of a temporary:
#include <iostream>
int main()
{
int a = 1;
int&& b = std::move(a);
int&& c = b + 1;
b = b + 1;
c = c + 1;
std::cout << a << b << c;
}
The output is:
223
QObject::sender() is a slow function
I did not expect that its share of CPU usage in my app is 12.15%:
Why does it iterate over some collection? Isn’t there only one sender in a thread?
(more…)Building QT 6.3.1 with OpenSSL for Windows
After various experimentation I was able to build QT 6.3.1 with OpenSSL for Windows with the following steps:
Extract archives with Bash:
tar -xzf ../distrib/openssl-1.1.1q.tar.gz
tar -xf ../distrib/qt-everywhere-src-6.3.1.tar.xz
Building OpenSSL 1.1.1q
Run the following commands with x64 Native Tools Command Prompt for VS 2022:
set PATH=%PATH%;C:\dev\PFiles\Strawberry\perl\bin
set PATH=%PATH%;C:\dev\PFiles\nasm-2.15.05
perl Configure VC-WIN64A
Experimentation with OpenSSL and QT configuration on Windows
Building OpenSSL 1.1.1q with custom installation directory
Run the following commands with x64 Native Tools Command Prompt for VS 2022:
set PATH=%PATH%;C:\dev\PFiles\Strawberry\perl\bin
set PATH=%PATH%;C:\dev\PFiles\nasm-2.15.05
set MY_INSTALL_DIR=C:/dev/libs/OpenSSL
perl Configure VC-WIN64A --prefix="%MY_INSTALL_DIR%" --openssldir="%MY_INSTALL_DIR%"
Mining NEOXA on HiveOS with 3GB cards
The key to the success in mining NEOXA on HiveOS is knowing pool parameters that can be stratum+tcp://minenice.newpool.pw:1120, for example:
Handling messages from Binance Websocket streams
User Data Stream
To subscribe I query listen key:
POST /api/v3/userDataStream
connect to websocket wss://stream.binance.com:9443/stream and send the listen key with the following message :
{
"id": 1,
"method": "SUBSCRIBE",
"params": [
"<my listen key>"
]
}
When Binance accepts the subscription it sends:
{
"id": 1,
"result": null
}
Using std::future as a coroutine in C++20
In C++20 it is possible to do this:
std::future<int> compute(as_coroutine) {
int a = co_await std::async([] { return 6; });
int b = co_await std::async([] { return 7; });
co_return a * b;
}
std::future<void> fail(as_coroutine) {
throw std::runtime_error("bleah");
co_return;
}
int main() {
std::cout << compute({}).get() << '\n';
try {
fail({}).get();
} catch (const std::runtime_error &e) {
std::cout << "error: " << e.what() << '\n';
}
}