Recent questions tagged c++

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c++ - Tools to generate higher-quality error messages for template-based code?

Concepts, that would render these tools unnecessary, are not part of C++11. STLFilt would have been one ... messages Improving g++ output 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 base class destructor (virtual) is called when a derived class object is deleted?

A difference between a destructor (of course also the constructor) and other member functions is that, if a ... deleted. Thanks in advance! 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 is the function of this statement *(long*)0=0;?

In the following code, *(long*)0=0; is used along with the if clause, but what is its purpose? if(r.wid*r.ht < tot) *(long*)0=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++ - C++1y/C++14: Variable Template Specialization?

According to C++1y/C++14 N3690, does the type of a variable template specialization have to be the same as the ... 42> { static double y; }; 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++ - Allowing a "friend" class to access only some private members

Suppose I have three C++ classes FooA, FooB and FooC. FooA has an member function named Hello, I want to call this ... 0; // compile error } }; 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++ - convert unsigned char* to std::string

I am little poor in typecasting. I have a string in xmlChar* (which is unsigned char*), I want to convert this ... t find a way to convert 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++ - Write a function that accepts a lambda expression as argument

I have a method like this template<typename T, typename U> map<T,U> mapMapValues(map<T,U> old, T (f)(T,U) ... 2008 and Intel C++ compiler 11.1 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++ - Show window in Qt without stealing focus

I'm using the Qt library to show a slideshow on the second monitor when the user isn't using the second ... way to prevent this from happening? 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++ - Boost::Tuples vs Structs for return values

I'm trying to get my head around tuples (thanks @litb), and the common suggestion for their use is for ... that compensate for the ambiguity? 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 pass deleter to make_shared?

Since C++11, because of several reasons, developers tend to use smart pointer classes for dynamic lifetime objects. And ... <int>(12, deleter); 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++ - Implicit conversion failure from initializer list

Consider the snippet: #include <unordered_map> void foo(const std::unordered_map<int,int> &) {} int main() { ... EDIT fixed a couple of typos. 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++ - QByteArray to QString

I'm having issues with QByteArray and QString. I'm reading a file and stores its information in a QByteArray. The file ... ". How can I fix 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++ - Error: expected type-specifier before 'ClassName'

shared_ptr<Shape> circle(new Circle(Vec2f(0, 0), 0.1, Vec3f(1, 0, 0))); shared_ptr<Shape> rect(new Rect2f ... can be done to rectify this issue? 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 do I check if a StringStream variable is empty/null?

Just a quick question here guys. I've been searching to no avail so far. A bit more info here: stringstream ... was assigned a value or not. 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 get CMake to pass either std=c++14/c++1y or c++17/c++1z based on GCC version?

GCC 4.x doesn't accept the --std=c++14 switch for C++14 code - it takes --std=c++1y instead. ... correct switch according to the GCC version? 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++ - 'cl' is not recognized as an internal or external command,

I am trying to compile a hello world program in Qt Using Qt Creator. I am getting 'cl' is not recognized as ... it is showing the same error. 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++ - Custom Kernel GpuMat with float

I'm trying to write a custom kernel using GpuMat data to find the arc cosine of an image's pixels. ... access was encountered in function copy 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++ - Base64 encode using boost throw exception

I trying to use boost base64 encoder, I found an example but I got and exception typedef transform_width< ... MSVS2008 and boost 1.38 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 traverse all nodes of clang AST?

I can traverse the specific subtrees of clang AST using the recursivevisitor class but what I want to do is to ... with this. Thanks in advance. 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 get return value of an exe called by ShellExecute

How to get the return value of an exe which is called by shellexecute function. ShellExecute(NULL, NULL, TEXT ( ... value of "dpinstx86.exe". 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++ - Add extra include/lib paths to MinGW

I would like to add some extra include/lib directories besides the default ones for MinGW to search upon compilation ... Qt files by default? 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 #include directive correctly?

Is there any material about how to use #include correctly? I didn't find any C/C++ text book that explains ... get confused in dealing with 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++ - Lock Free Queue -- Single Producer, Multiple Consumers

I am looking for a method to implement lock-free queue data structure that supports single producer, and ... architecture. Thank you, Shirish 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++ - In what scenarios should I expect to explicitly need to implement a move constructor and move assignment operator?

Given that a class actually is moveable, manually implementing the move constructor and move assignment operator for a ... /09/12/10209291.aspx 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++ - Understanding the benefits of move semantics vs template metaprogramming

I've read some descriptions about move semantics in C++11 and I wonder in what context it could be used. Currently ... for that kind of use ? 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++ - Which rules determine whether an object is trivially copyable

With the introduction of c++11, trivially copyableness has gotten quite relevant. Most notably in the use of 'std:: ... ). So hereby my request. 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 can I use C++11 variadic templates to define a vector-of-tuples backed by a tuple-of-vectors?

Suppose I have a bunch of vectors: vector<int> v1; vector<double> v2; vector<int> v3; all of the ... This is not critically important though. 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 bind function to an object by reference?

I have the following code to bind a member function to an instance of the class: class Foo { public: int ... ? Can someone please explain 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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