Recent questions tagged C++

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c++ - Openmpi mpmd get communication size

I have two openmpi programs which I start like this mpirun -n 4 ./prog1 : -n 2 ./prog2 Now how do I use ... now I get "6" in both programs. 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 asio deadline_timer async_wait(N seconds) twice within N seconds cause operation canceled

What I want is when one message queue receives an int N, the handler function will be called after N seconds. below ... .join(); 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++ - Why comparing three variables together with == evaluates to false?

The output of the following program is "they are not equal", but I'd expect "they are equal" as the three compared ... they are not equal "; } } 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 the usual access control checking applies to names used to specify explicit instantiation when accessed through template parameters?

The C++11/14 standards state the following in note 14.7.2/12 [temp.explicit]: The usual access ... choices for the selected components. 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++ - glm returning nan on simple translate

I'm tinkering with OpenGL using glfw, glad, and glm. In one of the tutorials I'm using, they demonstrate ... . I greatly appreciate your time! 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 AES_cbc_encrypt add padding?

Consider the following snippet of C++ code: #include <iostream> #include <openssl/aes.h> #define AES_KEY_LENGTH ... to 47 in encryption_output? 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 does QHeaderView::paintSection do such that all I do to the painter before or after is ignored

This question is further development of this post and is different, though may seem similar as this one. I am trying ... painted as it is now... 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++ - Failure to deduce template argument std::function from lambda function

While exploring templates in C++, I stumbled upon the example in the following code: #include <iostream> #include ... general way to solve this? 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++ - include header file error: multiple definition

I have a very simple file system in a program. There is :main.cpp which include worker.h, worker.h ... the multiple definition linker error ? 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++ - ECDSA sign with OpenSSL, verify with Crypto++

I create an ECDSA keypair (secp128r1) in my application with Wei Dai's Crypto++. Signing and verifying works ... signature is 32 Byte exactly? 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++ - Class method for WndProc

This article explains brilliantly the options to call a class member WndProc. I've seen this response in ... first UnhookWindowsHookEx(hook); 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 my function returning garbage when it should return a char?

I'm a newbie in C++ learning the language and playing around. I wrote a piece of code which behavior I ... always print the same character..:S 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 needed to use BGL algorithms on existing data structures ( edges and vertices as vector<Object *>)?

I have custom data structures like this : vector<myVertex *> my_vertices; vector<myEdge *> my_edges; My class ... might not be that flexible. 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++ - Distance between istream_iterators

I am trying to count the amount of elements read by std::cin by using std::distance for the constructor ... affecting the stream. 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++ - Defining Global Variables Between Two .cpp Files

How can I share/globalize a bool variable between A.cpp and B.cpp where neither of them does include the ... inside those shared headers? 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++ - VS: unexpected optimization behavior with _BitScanReverse64 intrinsic

The following code works fine in debug mode, since _BitScanReverse64 is defined to return 0 if no Bit is ... this compiler intrinsic directly? 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 using CArray

So, I am trying to use CArray like this : CArray<CPerson,CPerson&> allPersons; int i=0; for(int i=0;i<10 ... where this is coming from. 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++ - Splitting a line of a csv file into a std::vector?

I have a function that will read a CSV file line by line. For each line, it will split the line into a vector ... 2. How can I correct this? 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 force child same virtual function call its parent virtual function first

guys, I have a case that needs the child class needs to call its parent virtual function at first before call ... there pattern on 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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c++ - Is it possible to access private members of a class?

Is it possible to access private members of a class in c++. provided you don't have a friend function ... have access to the class definition See Question&Answers more detail:os...

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

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334 views

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c++ - Difference in using read/write when stream is opened with/without ios::binary mode

In my experiments with the following code snippet, I did not find any particular difference whether i created the ... when doing file IO ? See Question&Answers more detail:os...

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

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158 views

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c++ - Alternative tokens (not, and, etc...) in VisualStudio 2013

The "not", "and", etc... are keywords in C++ (macros in C). Is there any way to "enable" them in ... not be able to recognize them as keywords. 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 cast a pointer to Derived class member function to the same but of class Base?

To me it looks perfectly safe to cast a void(Derived::*)() to a void(Base::*)(), like in this ... a template with template argument Derived). 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++ - The assignment operator and initialization

I'm studying the C++ programming language and I'm reading the chapter about assignment operator ( = ). In ... operator. Is it right ? 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 Task Manager a special kind of 'Always on Top' window for windows 10?

If my window has the 'always on top' extended style set, I would expect it to be on top of all ... as a value for hWndInsertAfter argument. See Question&Answers more detail:os...

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

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300 views

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c++ - Is there a performance penalty for passing "this" by value in Go methods?

I'm exploring Go after 9 years of C++ development. In C++ it is a bad practice to pass function's arguments by value ... Go as it is in C/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++ - Is there a `shared_lock_guard` and if not, what would it look like?

I wanted to use a std::mutex in my class, and noticed that it isn't copyable. I'm at the bottom ... oversight or trivial to implement myself? 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++ - Simple for() loop benchmark takes the same time with any loop bound

I'm willing to write a code that makes my CPU execute some operations and see how much time does he take ... CLOCKS_PER_SEC)*1000; 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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