The code below does not compile in C++:
template <class Result, class... Params>
class Slot
{
public:
virtual Result operator()(Params ... args) = 0;
};
Category Archives: Programming languages
Override one virtual function multiple times in C++
Why do we pass parameters to coroutines by value in C++?
C++ coroutines and const reference parameters
A coroutine func accepts a parameter by const reference in the code below:
#include <boost/asio.hpp>
#include <iostream>
namespace asio = boost::asio;
using asio::awaitable;
using asio::use_awaitable;
class Param
{
public:
Param(int val) : m_val(val)
{
std::cout << "Param constructor " << m_val << std::endl;
}
Using BOOST 1.89 with BOOST_ASIO_HAS_IO_URING on Linux
Added the following to the common section of CMake:
add_definitions("-DBOOST_ASIO_HAS_IO_URING")
and the following to the project section:
find_library(URING_LIB uring)
target_link_libraries(${TEST_TARGET} PRIVATE ${URING_LIB})
Investigating how LDAP works with Seal and Sign flags
C# code:
public void bindWithMs(string ldapServer, int ldapPort, string ldapUser, string ldapPassword)
{
var ldap = new System.DirectoryServices.Protocols.LdapDirectoryIdentifier(ldapServer, ldapPort);
using (var connection = new System.DirectoryServices.Protocols.LdapConnection(ldap))
{
connection.AuthType = System.DirectoryServices.Protocols.AuthType.Negotiate;
connection.Timeout = TimeSpan.FromSeconds(120);
connection.SessionOptions.ProtocolVersion = 3;
connection.SessionOptions.Signing = true;
connection.SessionOptions.Sealing = true;
connection.Credential = new System.Net.NetworkCredential(ldapUser, ldapPassword);
connection.Bind();
}
}
Increasing image size in WordPress
I updated my Ubuntu 24.04 and my WordPress stopped loading images of size 1.3MB and higher.
I fixed this by adding the following:
client_max_body_size 32M;
to Nginx configuration.
(more…)An example where we need const_cast in C++
class Example
{
public:
Example()
{
m.emplace("abc", 13);
}
const int& findValue(const std::string& val) const
{
auto i = m.find(val);
if (i == m.end()) {
throw std::runtime_error(std::format("Key {} not found.", val));
}
return i->second;
}
int& findValue(const std::string& val)
{
return const_cast<int&>(
const_cast<const Example*>(this)->findValue(val));
}
An Interface Segregation Principle (ISP) example
#include <iostream>
#include <memory>
#include <string>
#include <vector>
struct IObject {
virtual ~IObject() = default;
/// Returns the name of the object.
virtual std::string getName() const = 0;
/// Prints a textual description of the object.
virtual void describe() const = 0;
/// Eats another object.
virtual bool eat(IObject* other) = 0;
};
An investigation of why dynamic_cast violates LSP
Signal sender cast in QT
QT implies that the client code will do qobject_cast that is actually dynamic_cast:
awl::ProcessTask<void> MarketModel::coPlaceOrder(OrderPtr p)
{
// Update SQLite databse...
// ...
// QT signals are used in both C++ and QML.
// They works with QObject*, and they are not aware of concrete types.
QObject::connect(p.get(), &OrderModel::statusChanged, this, &MarketModel::onOrderStatusChanged);
}
Examples of const function parameters in C++
Examples with int
Compiles without warnings with MSVC:
class A
{
public:
void f(const int a);
};
void A::f(int a)
{
a = 10;
std::cout << a;
}
Investigating cobalt::generator
Standard C++ generator
The code below demonstrates how standard C++23 synchronous generator works:
#include <boost/cobalt.hpp>
#include <iostream>
#include <generator>
namespace cobalt = boost::cobalt;
std::generator<int> numbers()
{
for (int i = 1; i <= 5; ++i)
{
co_yield i;
}
}
