Recent questions tagged C++

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c++ - noexcept, stack unwinding and performance

The following draft from Scott Meyers new C++11 book says(page 2, lines 7-21) The difference between unwinding ... mentioned in the 2006 TR? 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 vector access operators are not specified as noexcept?

Why std::vector's operator[], front and back member functions are not specified as noexcept? 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 static_cast between char * and unsigned char *?

Apparently the compiler considers them to be unrelated types and hence reinterpret_cast is required. Why is this the rule? 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 require capturing 'this' to call static member function?

For the following code: struct B { void g() { []() { B::f(); }(); } static void f(); }; g++ 4 ... should be, I even qualified the call with B::. 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 we declare a namespace within a class?

Declaring a class within a class is valid. (Nested classes) Declaring a namespace within a class is invalid. The ... ) will be apreciated :) 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 difference between const and non const key?

What is the difference between the following two lines? map<int, float> map_data; map<const int, float> map_data; 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++ - Get Pixel color fastest way?

I'm trying to make an auto-cliker for an windows app. It works well, but it's incredibly slow! I'm ... Could you please help me? 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++ - zero initialization and static initialization of local scope static variable

I read several posts on C++ initialization from Google, some of which direct me here on StackOverflow. The concepts ... based on the code 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++ - converting cv::Mat for tesseract

I'm using OpenCV to extract a subimage of a scanned document and would like to use tesseract to perform OCR over ... , subImage.size().height); 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++ - const pointer assign to a pointer

Why can I not do this: char* p = new char[10]; void SetString(char * const str) { p = str; } SetString ... concat (MyString& a, MyString& b); }; 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 pan images in QGraphicsView

I am currently able to load my image into a grahpics scene, and then again into a QGraphicsViewer. I ... listener to the QGraphicsView object 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 I really have to worry about alignment when using placement new operator?

I read this When should I worry about alignment? but I am still do not know if I have to worry ... unaligned access cost more than aligned? 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 scope exit guard, a good idea?

I've written a small utility class for C++11 which I use as a scope guard for easier handling of exception ... this could throw return 0; } 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++ - Opening a window that has no title bar with Win32

I'm developing a C++ application for Windows. I'm using the Win32 API. How can I open a ... .SizableToolWindow; ControlBox = false; 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 std::string thead-safe with gcc 4.3?

I'm developing a multithreaded program running on Linux (compiled with G++ 4.3) and if you search ... everybody for an interesting discussion! 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 size of a pointer? What exactly does it depend on?

I searched online and while I could find a few discussions, I did not find a comprehensive description. So if anyone ... the size of a pointer? 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 move constructor?

I am trying some new C++11 features on visual studio 11, started with the move constructor. I wrote a ... the move constructor for MyClass? 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 you get the icon, MIME type, and application associated with a file in the Linux Desktop?

Using C++ on the Linux desktop, what is the best way to get the icon, the document description and the ... m looking for the long answer. 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++ - aligned_storage and strict aliasing

I'm currently using aligned_storage to implement an 'Optional' type similar to that of boost::optional. To accomplish ... sleep at night :P). 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++ - Difference between global non-throwing ::operator new and std::malloc

C++ has several functions to acquire dynamic storage, most of which differ in some fundamental way. Several more ... perform any ctor calls. 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++ - Accessing elements of a cv::Mat with at<float>(i, j). Is it (x,y) or (row,col)?

When we access specific elements of a cv::Mat structure, we can use mat.at(i,j) to access the element at ... the ith row and the jth column. 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++ - static_assert on initializer_list::size()

Why is std::initializer_list<_E>::size not allowable in a static_assert, even though it's declared as a constexpr in my ... no!"); return 0; } 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 determine the correct size of a QTableWidget?

Is there any way to set the "correct" size of a QTableWidget? (I'm a newbie) This test code is only 25 ... of tbl->width() unchanged at 640. 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++ - sizeof taking two arguments

In C.1.3 of the C++ IS (2003. It's in the C++11 IS, too), the standard points out a difference between ISO C ... , but a char[100] in C++. Why? 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++ - GLIBCXX versions

If I compile a C++ program on my machine, and run it on another one (with older software) I get: /usr/ ... against a given version of libstdc++? 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++ - Compile program for 32bit on 64bit Linux OS causes fatal error

Using gcc -m32 myprog.c should compile in 32 bit version the file myprog.c. Unfortunately I get this error: ... but uses 64 bit instructions. 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::make_tuple doesn't make references

I've been experimenting with std::tuple in combination with references: #include <iostream> #include <tuple> int main() ... 5 doesn't change 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++ - Will main() catch exceptions thrown from threads?

I have a pretty large application that dynamically loads shared objects and executes code in the shared object. As ... they are thrown from? See Question&Answers more detail:os...

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

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