Recent questions tagged C++

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c++ - What is the difference between a .cpp file and a .h file?

Because I've made .cpp files then transfered them into .h files, the only difference I can find is that ... any difference that I am missing? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why sizeof int is wrong, while sizeof(int) is right?

We know that sizeof is an operator used for calculating the size of any datatype and expression, and when ... sizeof int cause any ambiguity? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to Use Models with QML?

I have a GUI written in qml and c++. There are 2 comboboxes (qt control 5.1). Second combobox has to update ... I update qml's model on runtime? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to erase & delete pointers to objects stored in a vector?

I have a vector that stores pointers to many objects instantiated dynamically, and I'm trying to iterate through the ... 'm using VC++ 2008. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ lambdas how to capture variadic parameter pack from the upper scope

I study the generic lambdas, and slightly modified the example, so my lambda should capture the upper lambda's ... returned lambda "printer" } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Embed resources (eg, shader code; images) into executable/library with CMake

I am writing an application in C++ which relies on various resources in my project. Right now, I have the ... it natively on my ARM target. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why is std::vector::operator[] 5 to 10 times faster than std::vector::at()?

During program optimization, trying to optimize a loop that iterates through a vector, I found the following fact: ::std ... not "wipe" it out. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Double-Checked Lock Singleton in C++11

Is the following singleton implementation data-race free? static std::atomic<Tp *> m_instance; ... static Tp & ... } } return *instance; } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to easily make std::cout thread-safe?

I have a multi-threaded application, which heavily uses std::cout for logging without any locking. In such a ... tedious. Any better practice? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to "Reveal in Finder" or "Show in Explorer" with Qt

Is it possible to open a folder in Windows Explorer/OS X Finder and then select/highlight one file in that folder, ... " or "Show in Explorer". See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Lambda functions as base classes

Playing around with Lambdas I found an interesting behaviour that I do not fully understand. Supose I have a ... some light on this please? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What is a .h.gch file?

I recently had a class project where I had to make a program with G++. I used a makefile and for some ... problems when it wasn't cleaned up? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Exception running boost asio ssl example

I'm trying to run the SSL examples from boost::asio and I'm getting an "Invalid argument" exception ... would be greatly appreciated. Thanks! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - OpenCV: How to visualize a depth image

I am using a dataset in which it has images where each pixel is a 16 bit unsigned int storing the ... highlight these small depth differences? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - When is What bound to a VAO?

I've been learning OpenGL for three days and I can get stuff done but I feel like copy pasting without knowing ... of my VBOs stored in there? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What use are const pointers (as opposed to pointers to const objects)?

I've often used pointers to const objects, like so... const int *p; That simply means that you can't ... What possible use would that have? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Pointing to a function that is a class member - GLFW setKeycallback

I'm writing a GLFW app, in which I've wrapped the function calls into a simple class. I'm having ... in which this conversion is possible See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - std::enable_if : parameter vs template parameter

I'm building some input checker that needs to have specific functions for integer and/or double (for example ' ... wrong in the second version. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Check double variable if it contains an integer, and not floating point

What I mean is the following: double d1 =555; double d2=55.343 I want to be able to tell that d1 is an integer while ... way to do it in c/c++? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Restrict variadic template arguments

Can we restrict variadic template arguments to a certain type? I.e., achieve something like this (not real C ... accepts any type of parameter. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - BSTR to std::string (std::wstring) and vice versa

While working with COM in C++ the strings are usually of BSTR data type. Someone can use BSTR wrapper like ... , wslen); return wsdata; } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Is gcc std::unordered_map implementation slow? If so - why?

We are developing a highly performance critical software in C++. There we need a concurrent hash map and implemented one. ... (logn) vs O(1))! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - generic member function pointer as a template parameter

Consider this code: #include <iostream> using namespace std; class hello{ public: void f(){ cout<<"f"<<endl; } ... so I won't paste it here. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What are potential dangers when using boost::shared_ptr?

What are some ways you can shoot yourself in the foot when using boost::shared_ptr? In other words, what ... when I use boost::shared_ptr? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Unresolved external symbol "public: virtual struct QMetaObject const * __thiscall Parent

I inherited a class from QObject : class Parent: public QObject { Q_OBJECT QObject* ... (?qt_metacall@Parent@@UAEHW4Call@QMetaObject@@HPAPAX@Z) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - QVector vs QList

I have a list of integers that I need to iterate over but an array is inadequate. What are the ... adjacent memory positions, use QVector. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Non const lvalue references

Why can you do this int a; const double &m = a; But when you do this int a; double &m = a; you ... non-const references can't bind temp objects. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - OpenCV Orb not finding matches once rotation/scale invariances are introduced

I am working on a project using the Orb feature detector in OpenCV 2.3.1 . I am finding matches between 8 ... else{ ++matchCount; } } } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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