Recent questions tagged C++

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c++ - Difference between static_cast<char*> and (char*)

this is my first question :) I have one pile file, and I have open it like shown below ; ifstream in ( ... so that I can improve my question? 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++ - Where do sequence points come from?

I know that writing something like ++a = a++; Is not only unreadable but also violates the c/c++ ... problems' before finding them as bugs? 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++ - Using volatile to prevent compiler optimization in benchmarking code?

I am creating a little program measure the performance difference between containers of types boost::shared_ptr and boost:: ... copy.size(); } 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++ - Should std::move be used in return-statements for effeciency?

I cannot figure out if the std::move in the following code does anything good or that it is completely wrong? The class ... .7.3-1ubuntu1) 4.7.3 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++ - Signal execution order with Qt::QueuedConnection

I have two signals A and B emitted one after another from an object in thread X, and the two connected ... be executed in an arbitrary order? 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++ - Standard C++11 code equivalent to the PEXT Haswell instruction (and likely to be optimized by compiler)

The Haswell architectures comes up with several new instructions. One of them is PEXT (parallel bits extract) ... compilers in the future. 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++ - When exactly does the destruction of a temporary object happen in a function call?

This code compiles and executes. I know that we have undefined behaviour in the first case. But what ... the temporary object destroyed? 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 create a file only if it doesn't exist?

I wrote a UNIX daemon (targeting Debian, but it shouldn't matter) and I wanted to provide some way of ... which only involves std::streams. 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++ - Use getline() without setting failbit

Is it possible use getline() to read a valid file without setting failbit? I would like to use failbit so ... the last line basic_ios::clear 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 are function pointers type unsafe

First of all type-safe means that anything that a compiler can catch straight away if done incorrectly. Now, I ... like both are type safe. 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 the value of RAND_MAX always (2^n)-1?

I'm interested for C++, though I suspect that simply imports the C standard definition. I believe the answer is ... and upper bounds in boost. 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++ - Passing temporary object as parameter by value - is copy constructor called?

If a have a class with both standard and copy constructors class Ex{ //constructor definitions } and a function ... directly created "inside" F? 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++ - BOOST_FOREACH & templates without typedef

When I work with BOOST_FOREACH, there isn't a problem with simple templates as vector. But when I try to ... type. Is there any workaround? 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 disable auto declaration for non regular types?

UPDATE: There is a proposal to change the meaning of auto in certain situations. Implicit Evaluation of auto Variables ... ::vector<bool> v.) 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++ - Implicit conversion with operator

This is in part inspired by this question. When I write the code: void test(std::string inp) { std::cout << ... not for the case of an operator? 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++ - disable c++11 features in vs2013

Is there a way to disable c++11 features when writing code in vs 2013 , I want my code to also compile on ... in the drop down menu there . 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++ - Limit scope of #define labels

What is the correct strategy to limit the scope of #define labels and avoid unwarranted token collision? In the ... proposed solution below.. __ 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 it mean to be "terminated by a zero"?

I am getting into C/C++ and a lot of terms are popping up unfamiliar to me. One of them is a variable or ... memory to be terminated by a zero? 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 would be a good implementation of iota_n (missing algorithm from the STL)

With C++11, the STL has now a std::iota function (see a reference). In contrast to std::fill_n, std::generate_n, ... in C++11 compared to C++98. 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++ - Determining if a string is a double

I would like to see if a string contains a double as its sole contents. In other words, if it could possibly be the ... < num; return s.str(); } 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 disable return value optimization in Visual Studio 2010?

Is it possible to disable RVO (return value optimization) in Visual Studio 2010? Setting optimization flag ... constructors which disables RVO. 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++ - Keeping a valid vector::iterator after erase()

EDIT: I have had a lot of answers telling me that I should separate the deletion into another loop. Perhaps ... process from the updating loop. 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++ - Using boost::assign::list_of

This compiles: std::vector<int> value = boost::assign::list_of(1)(2); But not this: ... constructor overload resolution was ambiguous 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++ - Specializing function template for reference types

Why is the output of this code : #include <iostream> template<typename T> void f(T param) { std::cout << ... want to learn the logic behind 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++ - How do the operators < and > work with pointers?

Just for fun, I had a std::list of const char*, each element pointing to a null-terminated text string, and ... , so you never really know... 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++ - Explicit instantiation of templated constructor for template class

I am uncertain if it is a bug in Clang 3.2 or a violation of C++03, but it appears that explicit instantiation ... standard or a bug in clang++? 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++ - OpenMP tasks in Visual Studio

I am trying to learn OMP library task based programming and as an example I copied and pasted the code below taken from a ... n, fib(n)); } } 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++ - Why does the ternary operator prevent Return-Value Optimization?

Why does the ternary operator prevent Return-Value Optimization (RVO) in MSVC? Consider the following complete ... , and optimize accordingly? See Question&Answers more detail:os...

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

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