The code below compiles with a warning:
#include <iostream>
#include <limits>
#include <cstdint>
int main()
{
int64_t m1 = -std::numeric_limits<int64_t>::min();
int64_t m2 = -m1;
std::cout << m1 << std::endl << m2 << std::endl << std::numeric_limits<int64_t>::max() << std::endl;
return 0;
}
When a link is dragged from a browser on Window 10 platform it contains the page title, but they did not make it accessible in QML:
import QtQuick 2.15
import QtQuick.Controls 2.15
ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Scroll")
id: root
DropArea {
id: dropArea;
anchors.fill: parent
onEntered: {
root.color = "gray";
drag.accept (Qt.LinkAction);
}
#include <iostream>
template <typename T>
void PrintValue(T val)
{
if constexpr (std::is_signed_v<T>)
{
std::cout << "signed";
}
else
{
std::cout << "unsigned";
}
std::cout << std::endl << val << std::endl;
}
At 10/20/2020:
And std::vector is not constexpr yet:
And there is no text formatting also.
Coroutines:
std::chrono::days:
It is possible to do this in QML:
Item
{
property var refreshChart: function () {}
Component.onCompleted:
{
refreshChart = function ()
{
console.log("Hello!")
}
}
}
Consider the declaration of a class that contains a lambda function or a reference to it:
#include <utility>
template <class Func>
struct Holder
{
Holder(Func && func) : m_func(std::forward<Func>(func))
{
}
Func m_func;
};
template <class Func>
auto MakeHolder(Func && func)
{
return Holder<Func>(std::forward<Func>(func));
}
I did some research on why my QT app crashes at the destructor of std::thread on Android 10 devices at the user side with the following call stack:
#00 /apex/com.android.runtime/lib64/bionic/libc.so (abort+160)
#01 /system/lib64/libc++.so (abort_message+232)
#02 /system/lib64/libc++.so (demangling_terminate_handler()+44)
#03 /system/lib64/libc++.so (std::__terminate(void (*)())+12)
#04 /system/lib64/libc++.so (std::terminate()+52)
#05 /system/lib64/libc++.so (std::__1::thread::~thread()+20)
#06 /apex/com.android.runtime/lib64/bionic/libc.so (__cxa_finalize+212)
#07 /apex/com.android.runtime/lib64/bionic/libc.so (exit+24)
#08 /data/app/com.domain.myapp-Rs_sm5VrLR1Jj8QW6oYByA==/lib/arm64/libplugins_platforms_qtforandroid_arm64-v8a.so
and figured out that its likely because std::thread destructor is being invoked while the thread is still joinable at some point of the application execution (thanks to G. M. on stackoverflow.com).
(more…)I wrote a simple test that outputs std::memmove speed to the console:
AWT_ATTRIBUTE(size_t, element_count, 1000000);
std::unique_ptr<uint8_t> p_src(new uint8_t[element_count]);
std::memset(p_src.get(), 25u, element_count);
std::unique_ptr<uint8_t> p_dst(new uint8_t[element_count]);
context.out << _T("std::memmove: ");
awl::StopWatch w;
std::memmove(p_dst.get(), p_src.get(), element_count);
ReportSpeed(context, w, element_count);
context.out << std::endl;
And the similar tests for std::memset and std::vector::insert.
(more…)In the code below, static_assert operates on the addresses of local variables, but however MS compiles it and the assertion does not fail:
#include <tuple>
#include <string>
struct A
{
int a;
double b;
std::string c;
};
void f()
{
A a{ 1, 3.0, "abc" };
constexpr auto t1 = std::tie(a.a, a.b, a.c);
static_assert(&std::get<0>(t1) == &a.a);
}
Use the following command to compile this example:
cl /std:c++17 /EHsc a.cpp
Consider the following scenario: there was structure A in an old version of a C++ application:
struct A
{
double a;
int b;
std::string c;
};
An instance of A was serialized into a file in a binary format and after that the application was updated to a new version.
But in the new version of the application structure A was modified by adding fields d and e and deleting field a:
struct A
{
int b;
std::vector<int> d;
bool e;
std::string c;
};
and the new version of the application needs to deserialize an instance of its new structure A from the file containing old version of A.
(more…)