Recent questions tagged C++

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c++ - Why is std::cout not printing the correct value for my int8_t number?

I have something like: int8_t value; value = -27; std::cout << value << std::endl; When I run my ... correct value. Does anyone have any 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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c++ - How to disable buffering on a stream?

In C, I can easily set a stream to unbuffered I/O: FILE * f = fopen( "test", "r" ); setvbuf( f ... similarly unbuffered I/O using C++ IOStreams? 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++ - Setting the Cursor Position in a Win32 Console Application

How can I set the cursor position in a Win32 Console application? Preferably, I would like to avoid making a ... I should be doing? 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++ - "Undefined symbols" linker error with simple template class

Been away from C++ for a few years and am getting a linker error from the following code: Gene.h #ifndef ... C++ for fun and practice. 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 there any use for local function declarations?

Most C++ programmers like me have made the following mistake at some point: class C { /*...*/ }; ... : expression must be a modifiable lvalue 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 reason for not being able to deduce array size from initializer-string in member variable?

Consider the code: struct Foo { const char str[] = "test"; }; int main() { Foo foo; } It fails ... -class const C-like null terminated string. 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++ - Does resizing a vector invalidate iterators?

I found that this C++ code: vector<int> a; a.push_back(1); a.push_back(2); vector<int>::iterator it = a. ... print 1. Can you explain it to me? 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 does Excel successfully round floating point numbers even though they are imprecise?

For example, this blog says 0.005 is not exactly 0.005, but rounding that number yields the right result. ... incorrect for the above 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++ - Detect GCC compile-time flags of a binary

Is there a way to find out what gcc flags a particular binary was compiled with? 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++ - STL containers element destruction order

Does ISO C++ standard mandate any sort of destruction order of objects inside STL containers? Are std::list/std:: ... its value (or vice versa)? 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++ - Multiple Inheritance from two derived classes

I have an abstract base class which acts as an interface. I have two "sets" of derived classes, which ... am still open to suggestions. 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 these members have unspecified ordering?

A colleague told me that, in the following type, all members have unspecified ordering in memory (relative to one another ... public: int z; }; 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++ - Cast vector<T> to vector<const T>

I have a member variable of type vector<T> (where is T is a custom class, but it could be int as well.) ... t compile for me. 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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211 views

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c++ - Read into std::string using scanf

As the title said, I'm curious if there is a way to read a C++ string with scanf. I know that I can ... also doesn't work. 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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290 views

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c++ - How do I find out if a tuple contains a type?

Suppose I want to create a compile-time heterogenous container of unique types from some sequence of non-unique types ... the STL or boost. See Question&Answers more detail:os...

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

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362 views

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c++ - How can std::unique_ptr have no size overhead?

If the size of an empty class can't be 0, what magic is doing std::tuple so the sizeof of unique_ptr is returning 8 in ... .7.1 (Debian 4.7.1-7) 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++ - Lifetime of lambda objects in relation to function pointer conversion

Following this answer I'm now wondering what the rules are for the lifetime of lambdas and how the relate ... retFun2() is undefined behaviour. See Question&Answers more detail:os...

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

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250 views

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c++ - Set all bytes of int to (unsigned char)0, guaranteed to represent zero?

This is not a matter of recommended practise (nor undefined behavior), but about what the c++-standard ... representation has all zero bits. See Question&Answers more detail:os...

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

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359 views

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c++ - non-defaulted operator <=> doesn't generate == and != in C++20

I'm running into a strange behavior with the new spaceship operator <=> in C++20. I'm using Visual Studio 2019 ... , but the custom one doesn't. 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++ - OpenCV threshold with mask

I'm trying to use OpenCV's cv::threshold function (more specific THRESH_OTSU), only that I'd like to do it ... make it inappropriate in my case. See Question&Answers more detail:os...

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

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195 views

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c++ - cpu dispatcher for visual studio for AVX and SSE

I work with two computers. One without AVX support and one with AVX. It would be convenient to have my code find ... at least it does not crash. See Question&Answers more detail:os...

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

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313 views

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c++ - Why is NVIDIA Pascal GPUs slow on running CUDA Kernels when using cudaMallocManaged

I was testing the new CUDA 8 along with the Pascal Titan X GPU and is expecting speed up for my code but ... I observing this kind of result? See Question&Answers more detail:os...

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

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240 views

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c++ - If temporaries are implicitly non-modifiable, how does this work?

I'm told that, in C++03, temporaries are implicitly non-modifiable. However, the following compiles for ... temporaries binding to references.) 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 get a Windows symbol server set up

I have a spare server on the network that I'd like to have host all of our build symbols. I already know how ... a step that I may be missing? See Question&Answers more detail:os...

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

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213 views

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c++ - How is heap and stack memories managed, implemented, allocated?

In C/C++ we can store variables, functions, member functions, instances of a class either on a stack or a heap. ... that... thanks for the link See Question&Answers more detail:os...

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

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267 views

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c++ - does (w)ifstream support different encodings

When I read a text file to a wide character string (std::wstring) using an wifstream, does the stream ... if that makes a difference) See Question&Answers more detail:os...

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

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313 views

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c++ - What the heque is going on with the memory overhead of std::deque?

I am working on an external sorting algorithm that uses std::queue and must carefully constrain its memory usage. ... std::deque by Microsoft? See Question&Answers more detail:os...

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

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320 views

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c++ - Is it bad practice to allocate memory in a DLL and give a pointer to it to a client app?

I'm using an exe which dynamically loads a DLL. A function in the DLL allocates memory on the heap and ... memory inside the DLL itself. See Question&Answers more detail:os...

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

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