Recent questions tagged C++

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c++ - long long implementation in 32 bit machine

As per c99 standard, size of long long should be minimum 64 bits. How is this implemented in a 32 bit machine ( ... of long long in 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++ - Why isn't RVO applied to base class subobject initialization?

Why is the move constructor for Base mandatory in case of inheritance (class B) in the following code (both in ... is deleted" }; #endif 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++ - Why does adding 0 to the end of float literal change how it rounds (possible GCC bug)?

I discovered on my x86 VM (32 bit) that the following program: #include <stdio.h> void foo (long double ... the constant this question is about. 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 NaN a valid key value for associative containers?

Consider the ordered and unordered associative containers in C++ keyed on double. Is NaN a valid key type? ... keys in associative containers.) 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 deal with global-constructor warning in clang?

Clang warns (when using -Weverything or Wglobal-constructors) about constructors for static objects. warning: ... / triggers said warning 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 check memory allocation failures with new operator?

Just recently I switched the language of my project to use C++ from C. With C, I used malloc and after ... +? Any advice will be appreciated. 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++ - small string optimization for vector?

I know several (all?) STL implementations implement a "small string" optimization where instead of storing the usual 3 ... a string. Good idea? 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 make std::make_unique a friend of my class

I want to declare std::make_unique function as a friend of my class. The reason is that I want to declare my ... as a friend of my class? 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 are std::vector::data and std::string::data different?

Vector's new method data() provides a const and non-const version. However string's data() method only provides ... behavior if it's empty. 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 isn't std::array::size static?

The size of std::array is known at compile time, but the size member function isn't static. Is there any ... classes derived from std::array.) 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 do we even need the "delete[]" operator?

This is a question that's been nagging me for some time. I always thought that C++ should have been ... ] was a small memory optimization. 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++ - _iterator_debug_level value '0' doesn't match value '2'

I've just moved over a Visual Studio (C++) solution over to another computer, setup all the directories and ... sure what to do about 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++ - variable or field declared void

I have a function called: void initializeJSP(string Experiment) And in my MyJSP.h file I have: 2: void ... void Where is the problem? 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++ - Adding an include guard breaks the build

I added #ifndef..#define..#endif to a file of my project and the compiler fails. As soon as I remove it or ... that is how the example did 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++ - How to calculate boolean expression in Spirit

I found a really good example about boolean translator, * Boolean expression (grammar) parser in c++ What I am thinking ... endl; } 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++ - Qt 5.2 Model-View-Pattern: How to inform model object about changes in underlying data structure

I have a class used for permanent storage of some item that are organized in a table-like manner. This ... moves forward, too. Matthias 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 happened to my SFINAE" redux: conditional template class members?

I'm new to writing template metaprogramming code (vs. just reading it). So I'm running afoul of some noob ... . Is there a better 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++ dynamic array initialization with declaration

I have function like this: void findScarf1(bool ** matrix, int m, int n, int radius, int connectivity); and ... spent 1.5 hours figuring it out 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++ - Disable sleep mode in Windows Mobile 6

Does anyone know how could I programatically disable/enable sleep mode on Windows Mobile? 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++ - How can I read from memory just like from a file using iostream?

I have simple text file loaded into memory. I want to read from memory just like I would read from a disc like ... with file in 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++ - Why is the new operator allowed to return *void to every pointer-type?

In C++ it is not allowed to assign an void* pointer to any integral pointer without an explicit cast. This requires ... int*' [-fpermissive]". 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++ - Creating and deallocating a Qt widget object

I heard that the widgets should be allocated on the heap (using new), and then there are no needs to ... deleted when its parent is deleted. 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++ - Boost.Python: Wrap functions to release the GIL

I am currently working with Boost.Python and would like some help to solve a tricky problem. Context When a ... any suggestion to this problem. 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 can I store a value at a specific location in the memory?

Maybe this is an easy question question but I would really like to know it for sure. If I want to store a ... . I am thankful for all help. 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++ - Wrap overloaded function via std::function

I have an overloaded function which I want to pass along wrapped in a std::function. GCC4.6 does not find a " ... = test; return func(); } 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++ - GetClipboardData(CF_TEXT)

How to use GetClipboardData(CF_TEXT); without calling and use process id of this in C++? and which ... GetClipboardData(CF_TEXT) belong to? 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++ - unsigned to signed conversion

Consider the following: #include <iostream> int main() { unsigned int x = 3; unsigned int y = 5; std::cout ... 14ubuntu5) 4.4.5 Thanks, Somebody 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++ - Mapping elements in 2D upper triangle and lower triangle to linear structure

I have a matrix M which is of NxN dimensions, where M(i,j) = M(j,i) I would like to represent this structure as a ( ... = K[.....]); 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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