Recent questions tagged C++

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Consider this simple hierarchy: class Base { public: virtual ~Base() { } }; class Derived : public Base { } ... specify how it actually works). See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Eclipse CDT: no rule to make target all

My Eclipse CDT keeps complaining "make: *** no rule to make target all" when I am trying to compile the piece ... answers help... Thanks a lot! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Optional function parameters: Use default arguments (NULL) or overload the function?

I have a function that processes a given vector, but may also create such a vector itself if it is not ... it, apart from programmer laziness? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to use std::atomic<> effectively for non-primitive types?

The definitions for std::atomic<> seem to show its obvious usefulness for primitive or perhaps POD-types. When ... avoid using it for classes? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - is there any way to disable compiler optimisation for a specific line of code?

is there any way to disable compiler optimisation for a specific line of code in Visual studio? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why does Qt use its own make tool, qmake?

I just started using Qt and noticed that it uses its own make tool, qmake. Why does Qt use its own make tool ... call the GCC C++ compiler? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - immutable strings vs std::string

I've recent been reading about immutable strings Why can't strings be mutable in Java and .NET? and Why . ... ever make it into boost? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Linker returns "relocation has an invalid symbol at symbol index..."

I am trying out some code on Ubuntu. I'm trying to run the following code #include <cstdlib> #include < ... would be really helpful! Thanks! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Vector: initialization or reserve?

I know the size of a vector, which is the best way to initialize it? Option 1: vector<int> vec(3); //in ... Option1. Is it? Any other options? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What's the difference between std::multimap<key, value> and std::map<key, std::set<value> >

I found that they have one key and multiple values which is unique. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why can't a derived class pointer point to a base class object without casting?

I have seen few Pet and Dog type examples for this type of basic question here and here, but they do ... terms of technical details. Thanks! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - send RSA public key to iphone and use it to encrypt

I have a TCP socket server and I want to do the following w/o using SSL: On server, make RSA key pair (I know ... how to do 2~4. Anyone knows? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Do Sub-Classes Really Inherit Private Member Variables?

Basically as far as I know, when you create a base class with a public, protected, and private ... apart my understanding of inheritance. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Python ctypes: how to free memory? Getting invalid pointer error

I want to get some string from a C/C++ library with ctypes into python. My code looks like this: ... : invalid pointer: 0x00000000026443fc *** See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - reprojectImageTo3D() in OpenCV

I've been trying to compute real world coordinates of points from a disparity map using the reprojectImageTo3D() ... ); return point3f; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Writing a virtual webcam?

I need to create a virtual webcam that poses as a webcam, but takes as input a set of images that it plays. ... What would the flow look like ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to translate a virtual memory address to a physical address?

In my C++ program (on Windows), I'm allocating a block of memory and can make sure it stays locked ... will be much appreciated!! Thanks See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Sending large amount of data between Qt threads

I have a QThread which generates a fairly large amount of data regularly (couple of megabytes per second), ... it under various OSs. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why is valarray so slow?

I am trying to use valarray since it is much like MATLAB while operating vector and matrices. I first did some performance ... ------------- See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What does `*&` in a function declaration mean?

I wrote a function along the lines of this: void myFunc(myStruct *&out) { out = new myStruct; out->field1 = 1; ... can't make much sense of it. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - If the address of a function can not be resolved during deduction, is it SFINAE or a compiler error?

In C++0x SFINAE rules have been simplified such that any invalid expression or type that occurs in the "immediate ... a little better? Thanks! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - QTcpSocket state always connected, even unplugging ethernet wire

I have a QTcpSocket and I am reading into a loop. Each time a full packet has been read, or there has been ... return false; } return true; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Xcode 4.3 and C++11 include paths

I installed Xcode 4.3 and want to test this C++11 program: #include <type_traits> int main() { } However, ... /usr/include/c++/v1/type_traits See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Performance difference between ++iterator and iterator++?

My workmate claims that for object types preincrement is more efficient than post increment e.g. std::vector<std::string> ... end(); it++){ } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to detect if a method is virtual?

I tried to make a traits to find if a method is virtual: (https://ideone.com/9pfaCZ) // Several structs ... detect if a method is virtual ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why can I access a derived private member function via a base class pointer to a derived object?

#include<iostream> using namespace std; class base { public: virtual void add() { cout << "hi"; } }; class ... ? Somehow it doesn't seem right. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why can't we initialize class members at their declaration?

I wonder if there is a reason why we can't initialize members at their declaration. class Foo { int ... any official clarification about this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Get a pointer to object's member function

Here is the problem: 1) I have a class like so: class some_class { public: some_type some_value; int some_function( ... , int, int, void*); See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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