Recent questions tagged C++

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c++ - How do I clear a Direct2D render target to fully transparent

I'm trying to draw semi-transparent rectangles on an invisible HWND. However, clearing the window with ... ; 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++ - Is there a way to define variables of two different types in a for loop initializer?

You can define 2 variables of the same type in a for loop: int main() { for (int i = 0, j = 0; i ... overhead (but it might be slow to compile). 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++ - shrinking a vector

I've got a problem with my terrain engine (using DirectX). I'm using a vector to hold the vertices of a ... try this: vertexvector.reserve(16); 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++ - Non interactive items in QMenu

I'm trying to build a menu with some items that are not interactive in QT. I subclass QMenu in my MyCustomMenuClass. ... idea on how to do 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++ - non-const pointer argument to a const double pointer parameter

The const modifier in C++ before star means that using this pointer the value pointed at cannot be changed, while ... we pass a non-const char* 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++ - cannot specify explicit initializer for arrays

I'm getting the following compile error... error C2536: 'Player::Player::indices' : cannot specify explicit initializer for ... 0f, 1.0f ) } } 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 end up with a pointer to 0xCCCCCCCC

The program I'm working on crashes sometimes trying to read data at the address 0xCCCCCCCC. Google (and ... pointing to 0xCCCCCCCC? 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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c++ - Regarding lvalue-to-rvalue conversion, when is it required?

I've been reading quite many on the Internet and it seems that many people mentioned the following rules ( ... expression Thanks for reading. 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++ - Getline ignoring first character of input

I'm just starting with arrays in C++ and I'm having a problem getting the first character of an array. This is ... 'J'. What am I doing 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++ - Bitwise shift operation on a 128-bit number

Lets say that I have an array of 4 32-bit integers which I use to store the 128-bit number How can I ... on this 128-bit number? 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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216 views

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c++ - What is __m128d?

I really can't get what "keyword" like __m128d is in C++. I'm using MSVC, and it says: The __m128d data ... type at all. Can someone shine me? 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++ - A timer for arbitrary functions

I tried to build a function template that can measure the execution time of functions of arbitrary type. Here is ... in the first place?) 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++ - invalid types 'int[int]' for array subscript

This code throws up the compile error given in the title, can anyone tell me what to change? #include <iostream> ... "); } 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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153 views

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c++ - Is it possible to build a heatmap from point data at 60 times per second?

I'm working on a simulation for clouds (actual clouds) where the clouds are simulated by 3D points, then ... to memory lookup I think. 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++14: Generic lambda with generic std::function as class member

Consider this pseudo-snippet: class SomeClass { public: SomeClass() { if(true) { fooCall = [](auto a){ ... store generic lambdas in a class? 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 does const auto and auto const apply to pointers?

I was try out some code and am wondering how the const qualifier in C++ applies to pointer types when using ... of the end pointer type. See Question&Answers more detail:os...

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

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315 views

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c++ - QObject::deleteLater across a QThread

I'm looking for a solution to schedule the deletion of an object across threads. The docs about how ... call deleteLater from any thread. See Question&Answers more detail:os...

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

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442 views

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c++ - Efficiency of vector index access vs iterator access

I have question to correct my understanding of efficiency of accessing elements of a vector by using index access ... to "accesses efficiency". See Question&Answers more detail:os...

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

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162 views

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c++ - How to use a macro in an #include directive?

I'm confused on how to use macros in the #include directive. I've done this: #include "../../../. ... ARCH_S to my #include directive string? 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++ - Warning about hiding member variables?

The following code snippet has a memory leak that I spent too much time chasing down. The problem is that inside ... to prevent copy/assign. } See Question&Answers more detail:os...

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

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644 views

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c++ - Is accessing the raw pointer after std::vector::reserve safe?

This is pretty farfetched, but is the following code "safe" (i.e. guaranteed not to cause segmentation ... original memcpy with memset. See Question&Answers more detail:os...

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

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290 views

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c++ - Why is this copy constructor called rather than the move constructor?

The following code snippet causes the copy constructor to be called where I expected the move constructor to be ... Is this standard behaviour? See Question&Answers more detail:os...

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

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407 views

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c++ - function implementation with enable_if outside of class definition

So basically, I have a very basic generic class for now, currently testing the type_traits header. I am currently trying ... w64 with -std=c++17 See Question&Answers more detail:os...

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

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233 views

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c++ - Forward declaration of objects with STL containers

Consider the following code snippet, where the first line serves only as forward declaration class A; followed by ... I am using? 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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c++ - What does `Fatal Python error: PyThreadState_Get: no current thread` mean?

I am passing an mpi communicator from python to C. I chose to use boost's mpi communicator as mpi4py does not ... * End of error message *** See Question&Answers more detail:os...

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

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402 views

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c++ - Linker error: undefined reference to `std::ctype<char>::_M_widen_init()

I am getting linker error while trying to run a sample project. Could you let me know how can I fix this? Thanks in ... make: *** [opt] Error 2 See Question&Answers more detail:os...

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

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222 views

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c++ member function pointer problem

I'm new to c++ . I want to know about object pointer and pointer to member function . I wrote a code ... them ? Please explain me these concept. 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++ - Non null-terminated string compiler option for gcc

Update turns out this is just another case of "c++ is not c blues" What I want const char hex[16] = " ... I can make a(n) constant array See Question&Answers more detail:os...

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

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