Recent questions tagged C++

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c++ - Using unique dynamic variable names (not variable values!)

Ok so, this is more a sanity check than anything else. Lets asume we have a struct called lua_State, now I ... blows over? 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++ - Clang skips processing of an initializer list construction

If you look at the following code, I think that both the lines in main() should call the initializer_list ... FITNESS FOR A PARTICULAR PURPOSE. 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++ - Flag '-l' in CMAKE_CXX_FLAGS doesn't work

I have some code I wrote on my mac machine and it has been working perfectly but when I port it over ... NTLM_WB SSL libz TLS-SRP UnixSockets 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++ - Error using custom operator< with std::less

I am trying to overload the < operator, but running into a problem. Here is my implementation: int ... ns3::Vector3D&)' discards qualifiers 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++ - Two constructors, which is default?

Okay I got a pretty simple assignment. I got these two constructors for class Person: Person( const string &, const ... or how does it work? 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++ - Force memory release to the OS

I have an app that takes about 20 MB of ram. In an seldom used algorithm it (std::vector) temporarily ... the memory back to the system? 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++ - Count the number of times each word occurs in a file

Hi I am writing a program that counts the number of times each word occurs in a file. Then it prints a list of ... return; } inFile.close(); } 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++ - CPP Error: Integer overflow in expression

I'm trying to represent 16gb in bytes, and uint64_t throws an error. What kind of data type should I use to represent ... * 1024 * 1024 * 1024; 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++ get registry key returns only one char

I'm trying to retrieve a value of a key but i'm only getting the first char of the value.. can anyone help? my ... } cout << data << endl; } 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++ - copy_graph - adjacency_list with bundled properties

Here is a complete snippet to copy a graph with bundled properties, but results in bunch of compiler errors. What ... copy_graph(grid, g1); } 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 it allowed to write an instance of Derived over an instance of Base?

Say, the code class Derived: public Base {....} Base* b_ptr = new( malloc(sizeof(Derived)) ) Base(1); ... validity of access via b_ptr->g(4) 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++ - CMake/Ninja attempting to compile deleted `.cpp` file

I've found that when I delete cpp files from my project using cmake and ninja, I can't easily compile it ... GLOB to generate lists of sources. 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 toupper on char returns the ascii number of the char, not the character?

int main() { char hmm[1000]; cin.getline(hmm, 1000); cout << hmm << endl; //this was to test if I ... the other ones as I have this problem. See Question&Answers more detail:os...

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

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175 views

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c++ - Boost regex not working as expected in my code

I just started using Boost::regex today and am quite a novice in Regular Expressions too. I have been ... with examples that explains this? See Question&Answers more detail:os...

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

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757 views

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c++ - Include guard and #pragma once in the same header file

Quoting from Microsoft documentation, There is no advantage to use of both the #include guard idiom and #pragma ... header files have both? See Question&Answers more detail:os...

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

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237 views

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c++ - std::string.resize() and std::string.length()

I'm relatively new to C++ and I'm still getting to grips with the C++ Standard Library. To help transition ... at all, no null bytes appear. 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 can I declare classes that refer to each other?

It's been a long time since I've done C++ and I'm running into some trouble with classes referencing ... a cyclical #include problem? 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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237 views

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c++ - Boost.Spirit mini_xml2.cpp example could not be compiled by C++11, Boost 1.55

c++0x compiler fails to compile boost.spirit example mini_xml2.cpp (and no errors from not c ... this macro #define BOOST_SPIRIT_USE_PHOENIX_V3 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++ - Avoid optimizing away variable with inline asm

I was reading Preventing compiler optimizations while benchmarking that describes how clobber() and escape() from ... godbolt.org/g/Ndd56K 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++ " undefined reference to 'Foo::Foo(std::string)' "

I'm not too familiar with c++ and how instantiating objects work, so this is probably a very simple thing to solve. ... foo("bar"); return 0; } See Question&Answers more detail:os...

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

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1.4k views

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c++ - How to convert QByteArray to std::istream or std::ifstream?

I want to create istream from QByteArray at runtime, without saving a physical file in memory of QByteArray. I ... . How to accomplish that? See Question&Answers more detail:os...

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

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295 views

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c++ - scanf not taking in long double

i have problem with scanf not reading long double in the code below: (please excuse my poor English) #include < ... fix it. 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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790 views

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c++ - SFINAE To detect non-member function existence

Does anybody know of a method for specializing a template depending on whether a non-member method is defined? I know there ... << "<NULL>"; } 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++ - Collision detection between 2 "linearly" moving objects in WGS84

[Complete re-edit by Spektre] based on comments I have two start points and velocity vectors in 3D (WGS84) how would I ... at time t= " << t; 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++ - g++4.9 and g++5 different behaviour when narrowing in initializing list

Consider this code: #include <iostream> int main() { int i{10.1}; // narrowing, should not compile std::cout < ... +11. Is this a known problem? See Question&Answers more detail:os...

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

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184 views

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c++ - How to use local classes with templates?

GCC doesn't seem to approve of instanciating templates with local classes: template <typename T> void f(T); void g( ... . How should it be done? See Question&Answers more detail:os...

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

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332 views

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c++ - std::istream operator exception reset / not thrown

I'm not sure about how to use std::istream::exception according to the standard, to let std::istream:: ... according to the C++ standard? See Question&Answers more detail:os...

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

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261 views

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c++ - SIMD: Accumulate Adjacent Pairs

I'm learning how to use SIMD intrinsics and autovectorization. Luckily, I have a useful project I'm working on ... level.) Thanks everyone. :) See Question&Answers more detail:os...

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

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