Recent questions tagged C++

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c++ how to elegantly use c++17 parallel execution with for loop that counts an integer?

I can do std::vector<int> a; a.reserve(1000); for(int i=0; i<1000; i++) a.push_back(i); std:: ... me to first fill a vector with ascending ints? 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++ - inline variable is initialized more than once

Im seeing some examples of inline const variable getting initialized (and destructed) 3 times with visual studio 2017. ... push for the bugfix) 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 do these two pointer subtractions give different results?

Consider the following code: char* p = new char[2]; long* pi = (long*) p; assert(p == pi); // ... in the debugger). Is this undefined behavior? 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++ - Detecting an unplugged capture device (OpenCV)

I'm attempting to detect if my capture camera gets unplugged. My assumption was that a call to cvQueryFrame would ... ...what am I missing? 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++ - Set processor affinity for MATLAB engine (Windows 7)

I'm developing an application in c++. One of the components of the application uses Matlab (via the Matlab ... /solutions, will be welcome. 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++ - Are C macros implicitly cast?

I've searched SO, but haven't found an answer to this specific questions. Forgive me if it's already been ... m not sure if this applies. 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++ - Pass temporary object to function that takes pointer

I tried following code : #include<iostream> #include<string> using namespace std; string f1(string s) { return s ... where I am thinking wrong? 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 boost asio sockets have proper RAII cleanup

I tried looking through source but I cant navigate that much of a template code. Basically: this is what ... it will be done automatically? 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 place header and ui file in different folders using autouic in cmake

According to the documentation, regarding autouic: If a preprocessor #include directive is found which matches ui_.h, ... success. Any ideas? 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 initialize to zero/NULL in a template

While writing a template, I want to initialize my variable to a value that serves as zero or null the the data type. ... the it serves as "0" ? 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++ - Scope of declarations in the body of a do-while statement

In Why can't you declare a variable inside a do while loop? the OP asks why a declaration in the while- ... -init (and while-init) scoping. 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++ - Mix boost::optional and std::unique_ptr

I admit it: I'm in love with the concept of optional. The quality of my code has improved so much ever ... due to lack of thorough testing). 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 test whether class B is derived from class A?

More specifically, let's say I have a class template with parameters A and B, and I would like to have a compiler ... (B is derived from A) }; 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 "CV_EXPORTS_W" means

Recently, I try to find out the source code of the "calcOpticalFlowPyrLK" function in OpenCV library. When I ... Anybody knows it's meaning? 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++ - Invoking a nonconst method on a member from a const method

I was surprised to find this "hole" in "const"ness: #include <stdio.h> class A { int r ; public: A():r(0) ... was in my code, where I found 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 undo a perspective transform for a single point in opencv

I am trying to do some image analysis using an Inverse Perspective Map. I used the openCV functions getTransform ... ) from the openCV library. 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++ - Any metaprogramming way to generate overloads for various numbers of template parameters?

I'm trying to create a set of function templates that can take different types and numbers of parameters, like this: ... do it for me instead? See Question&Answers more detail:os...

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

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189 views

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c++ - What is the minimum supported SSE flag that can be enabled on macOS?

Most of the hardware I uses supports SSE2 these days. On Windows and Linux, I have some code to test SSE support ... PDCM SSE4.1 SSE4.2 POPCNT 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 make a header-only library with cmake?

How to make a project in cmake that collects all c++ files into one header? I have this project structure. ... templates? The first is better. 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++ - Macports on OSX 10.9 - compile with -stdlib=libstdc++

In OSX 10.9 the default -stdlib option for clang++ is libc++, so that's what Macport uses when building ... do so for other packages as well 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 the Compiler does not detect correct function signature in error?

The question is in reference to this, which was posted a little while earlier. While the OP was happy accepting the ... to be the obvious case. 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++ - cudaDeviceSynchronize() error code 77: cudaErrorIllegalAddress

Thank you very much for reading my threads. I am doing CUDA work, but keep getting cudaDeviceSynchronize() ... Any comments is appreciated. 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 should I use g++'s -finput-charset compiler option correctly in order to compile a non-UTF-8 source file?

I'm trying to compile a UTF-16BE C++ source file in g++ with -finput-charset compiler option but I'm ... long change list in the commit dialog. 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 rvalue reference pass as lvalue reference?

pass() reference argument and pass it to reference, however a rvalue argument actually called the reference(int&) ... reference() as lvalue? See Question&Answers more detail:os...

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

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420 views

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c++ - How to read complete data in QTcpSocket?

Now the server (implemented with java) will send some stream data to me, my code is like below: connect(socket, ... work for me. Many 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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364 views

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c++ - Buidling boost error: Name clash for '<pstagelib>boost_system-vc120-mt-1_58.dll'

I'm trying to build boost on windows 8.1 with Visual Studio 2013 on 64bit system. b2 toolset="msvc" address- ... and how to resolve it? 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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400 views

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c++ - Is endian conversion required for wchar_t data?

In C/C++, if a multi-byte wide character (wchar_t) value is transmitted from a big-endian system to a little- ... the bytes need to be swapped? See Question&Answers more detail:os...

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

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564 views

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c++ - Using QT, how to call function once after a certain interval, even if more calls may occur?

I am having a hard time wording this question even though I don't think its that complicated. I want to ... multiple times before it fires. See Question&Answers more detail:os...

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

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