Recent questions tagged C++

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c++ - Is there a way to use pre-compiled headers in VC++ without requiring stdafx.h?

I've got a bunch of legacy code that I need to write unit tests for. It uses pre-compiled headers ... better way to approach 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++ - Why does constexpr static member (of type class) require a definition?

==> See the full snippet code and compilation on coliru. I have a LiteralType class filling constexpr requirements: ... as header files only) 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++ - Comparing two integers without any comparison

Is it possible to find the greatest of two integers without any comparison? I found some solutions: if(!(a ... and arithmetic operators. ThanX. 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 a '0' to an int digit allow conversion to a char?

I've seen examples of this all over the place: int i = 2; char c = i + '0'; string s; s += ... why adding the zero allows for the conversion. 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 File Scope and Global Scope

I am a student and I am confused about global and file scope variables in C and C++. Is there any ... If yes, please explain in detail. 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++ - Where does the __1 symbol come from when using LLVM's libc++?

I see a fair amount of questions like Apple Mach-O Linker (Id) Error and Undefined symbols in cryptopp at IOS ... that a rename does not occur. 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 double can store bigger numbers than unsigned long long?

The question is, I don't quite get why double can store bigger numbers than unsigned long long. Since both of ... smaller than DBL_MAX ... 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++ - What is an Anonymous Object?

What is an Anonymous Object exactly? Does C++ support/have Anonymous 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++ - What's the real use of using n[c-'0']?

I'm a novice in C and I came across the code like this : int n[10]; if(c>='0' && c<='9' ... what are the disadvantages well? Thanks in advance. 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 thread vs async performance (VS2013)

I feel like I'm missing something here... I slightly altered some code to change from using std::thread to std:: ... that as far as I'm aware) 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++ - Writing x264 from OpenCV 3 with FFmpeg on Linux

I'm having trouble writing h264 video with OpenCV 3 via FFmpeg ("'X','2','6','4'" FOURCC). I' ... but the resulting video is still unreadable. 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 have unary_function, binary_function been removed from C++11?

I found that binary_function is removed from C++11. I am wondering why. C++98: template <class T> struct ... in C++11 without unary_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++ - How to add code at the entry of every function?

I want to add some code before every function call to do some checking. The only way I know is: ... SOME_CODE" to every function manually. 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++ - error C2228: left of '.size' must have class/struct/union

I'm getting this compiler error when calling vector's size(). Why? #include <vector> #include <iostream> #include ... console view 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++ - Behaviour of negative zero (-0.0) in comparison with positive zero (+0.0)

In my code, float f = -0.0; // Negative and compared with negative zero f == -0.0f result will be true. ... -0 // Here print negative zero true 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++ - typeid() returns extra characters in g++

class foo { public: void say_type_name() { std::cout << typeid(this).name() << std::endl; } }; int main ... :endl; it prints 3foo. Any thoughts? 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++ - Segmentation Fault before main() when using glut, and std::string?

On 64-bit Ubuntu 14.04 LTS, I am trying to compile a simple OpenGL program that uses glut. I am ... glance doesn't reveal anything amiss. 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 put a variable declaration in the test portion of a while loop?

You can, obviously, put a variable declaration in a for loop: for (int i = 0; ... and I've noticed that you ... ... which is not what I want. 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++ - Redefining or changing macro value

I am currently working on an already developed project written in MFC C++ and am facing a problem with an ... help would be much 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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284 views

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c++ - How do I perform a pairwise binary operation between the elements of two containers?

Suppose I have two vectors std::vector<uint_32> a, b; that I know to be of the same size. Is there a C++ ... result in std::vector<uint_32> 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++ - SDL window does not show

This is my code: #include <iostream> #include <SDL2/SDL.h> int main(int argc, const char * argv[]) { ... is not hidden behind somewhere. Ideas? See Question&Answers more detail:os...

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

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186 views

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c++ - Why is it not possible to overload the ternary operator?

Why is it not possible to overload the ternary operator ' ?: '? I use the ternary operator often to consolidate if ... I know it cannot be done. 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++ - Partial template specialization based on "signed-ness" of integer type?

Given: template<typename T> inline bool f( T n ) { return n >= 0 && n <= 100; } When used ... template specialization would be legal anyway.) 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 my SFINAE expressions no longer work with GCC 8.2?

I recently upgraded GCC to 8.2, and most of my SFINAE expressions have stopped working. The following is somewhat ... 3: GCC bug report created 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 RAII to manage resources from a C-style API

Resource Acquisition is Initialization (RAII) is commonly used in C++ to manage the lifetimes of resources which ... the benefits of RAII. See Question&Answers more detail:os...

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

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119 views

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c++ - Address of function is not actual code address

Debugging some code in Visual Studio 2008 (C++), I noticed that the address in my function pointer variable is ... it a debugging "feature" ? See Question&Answers more detail:os...

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

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350 views

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c++ - fseek does not work when file is opened in "a" (append) mode

FILE* f = fopen("rajat", "w"); fputs("sometext", f); fseek(f, 6, SEEK_SET); fputs("is a", f ... the second code outputs exactly like the first? See Question&Answers more detail:os...

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

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211 views

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c++ - How to format a datetime to string using boost?

I want to format a date/time to a string using boost. Starting with the current date/time: ptime now = ... code to achieve this? 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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