Recent questions tagged C++

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c++ - Program behaving strangely on online IDEs

I have come across the below C++ program (source): #include <iostream> int main() { for (int i = 0; i < ... . Why 4169 and not some other value? 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++ - Initializing default values in a struct

If I needed to initialize only a few select values of a C++ struct, would this be correct: struct foo { foo() ... = true and an undefined bar.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++ - Object layout in case of virtual functions and multiple inheritance

I was recently asked in an interview about object layout with virtual functions and multiple inheritance involved. I ... c; }; 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 tracking using optical flow

I use this to functions as a base of my tracking algorithm. //1. detect the features cv:: ... using OpenCV optical flow function? 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++ - qt thread with movetothread

I'm trying to create a program using threads: the main start with a loop. When a test returns true, I create ... for the new thread's finish . 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++ - Do child threads exit when the parent thread terminates

I was doing some multithreaded programming in Visual studio C++ using the calls beginthreadex, endthreadex. I create a ... should this case be? 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++ - Copy a streambuf's contents to a string

Apparently boost::asio::async_read doesn't like strings, as the only overload of boost::asio::buffer ... contents without excessive copying? 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 the use of intptr_t?

I know it is an integer type that can be cast to/from pointer without loss of data, but why would I ever ... be a good use case for intptr_t? 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 the difference between MinGW, MinGW-w64 and MinGW-builds?

What are the differences between MinGW, MinGW-w64 and MinGW-builds? And which one should I use to compile c++ 11 ... IDE on a Windows 8 machine? 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++ - Easy way find uninitialized member variables

I am looking for an easy way to find uninitialized class member variables. Finding them in either runtime or ... member variables one by one. 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++ - Select class constructor using enable_if

Consider following code: #include <iostream> #include <type_traits> template <typename T> struct A { int val ... and move-constructor)? 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 doesn't emplace_back() use uniform initialization?

The following code: #include <vector> struct S { int x, y; }; int main() { std::vector<S> v; v. ... that is, everywhere - to initialize 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++ - How to define a string literal in gcc command line?

In gcc command line, I want to define a string such as -Dname=Mary, then in the source code I want printf("%s ... print Mary. How could I do it? 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 can't I create a vector of lambdas (of the same type) in C++11?

I was trying to create a vector of lambda, but failed: auto ignore = [&]() { return 10; }; //1 std:: ... , would work for me. Is this 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++ - Generating Java interface with SWIG

I'm using SWIG to make a Java wrapper of a C++ library (about Json (de)serialization) to use it on ... generate a valid interface with SWIG ? 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++ - Optimal lock file method

Windows has an option to open a file with exclusive access rights. Unix doesn't. In order to ensure exclusive ... wouldn't be atomic anymore. 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 do I tell CMake to use Clang on Windows?

I have a C++ project that builds using CMake. I usually build on OSX but now I am trying to get a ... which compiler CMake is configured with? 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 can you omit the file extension in an #include directive?

I'm playing around with gmock and noticed it contains this line: #include <tuple> I would have expected ... the directive a different meaning? 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++ - Initialise Eigen::vector with std::vector

I have seen it done before but I cannot remember how to efficiently initialize an Eigen::Vector of known ... method to perform this action. 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++ - Serializing and deserializing JSON with Boost

I'm newbie to C++. What's the easiest way to serialize and deserialize data of type std::Map using boost. ... but they are obscure for me. 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 do I deal with "signed/unsigned mismatch" warnings (C4018)?

I work with a lot of calculation code written in C++ with high performance and low memory overhead in ... simplicity of the underlying code. 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++ - Using hierarchy in findContours () in OpenCV?

When finding contours, I used the CV_RETR_CCOMP argument. This is supposed to create a two level hierarchy - the ... of cvFindContours ()). 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++ - Obtain a std::ostream either from std::cout or std::ofstream(file)

how do I bind a std::ostream to either std::cout or to an std::ofstream object, depending on a certain ... a better, exception-safe solution? 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::fill(0) slower than std::fill(1)?

I have observed on a system that std::fill on a large std::vector<int> was significantly and consistently ... -O3 -o fillbench_gcc -fopenmp. 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 the <iosfwd> header?

What's the <iosfwd> header used for? Why is it necessary? Any example? 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++ - C++11: Number of Variadic Template Function Parameters?

How can I get a count of the number of arguments to a variadic template function? ie: template<typename ... number_of_args in the above? 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++ - use std::fill to populate vector with increasing numbers

I would like to fill a vector<int> using std::fill, but instead of one value, the vector should contain numbers in ... // elements are set to 2 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++ - Questions about Hinnant's stack allocator

I've been using Howard Hinnant's stack allocator and it works like a charm, but some details of the ... current code C++11 conformant? See Question&Answers more detail:os...

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

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