Recent questions tagged c++

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c++ - Qt widget (with layout) space. What is it? How to remove?

I have written a program that uses widgets as container (for other widgets). Because the contents of the container ... return app.exec(); } 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++ - Avoiding infinite loop when a char is enter in place of int

I'm doing a Banking System project and need to make sure that every input is valid(program has to be robust) ... user for an input again? 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++ - Move constructors of STL containers in MSVC 2017 are not marked as noexcept

I am moving my project from VS2015 to VS2017, which of course does not go smoothly. I am seeing strange ... code only compiles with vector. 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 a bit field work with character types?

struct stats { char top : 1; char bottom : 1; char side : 2; } MyStat; I have seen this format with ... and what does it represent? Thank You. 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++ - Does reinterpret_casting an integral to a pointer type and back yield the same value?

According to http://en.cppreference.com/w/cpp/language/reinterpret_cast, it is known that reinterpret_cast a pointer ... yield the same value? 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 access the value of a local variable that has become hidden inside another scope?

I know if a variable is global, the you can always access its value by preceding the variable name with :: ... okay with some hacky solution. 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++ - Treating a single object like an array with one element, taking one-past-end pointer

Preamble: It is well-known that taking the pointer one past the end of an array is legal and well-defined: ... and well-defined by the 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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c++ - is_lock_free not defined in std::atomic<T> in gcc 4.7.2?

I encounter this compiler error function std::atomic::is_lock_free() const: error: undefined reference to '__atomic_is_lock_free ... () << 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++ - tilde operator returning -1, -2 instead of 0, 1 respectively

I'm kind of puzzled by this. I thought the ~ operator in C++ was supposed to work differently (not so ... will have some insight into 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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c++ - Access violation writing location when working with pointers to char

I am writing a very simple program that removes duplicate chars from a string. I ran it visual studio and got ... I still get the same error. 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 a default value of nullptr in a map of pointers defined behaviour?

The following code seems to always follow the true branch. #include <map> #include <iostream> class TestClass { // ... how would I 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++ - Are std::map and std::vector thread safe?

I am developing a multi threaded application, each thread will read (there will be no modifying of structures) ... structures are being read? 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++ - Set app to require elevation?

I'm working on the bootstrap application of a new installer for some of our products. So far, I've been ... where to make it require elevation. 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++ - Compile-time check to make sure that there is no padding anywhere in a struct

Is there a way to write a compile-time assertion that checks if some type has any padding in it? For example: ... of padding here int c; }; 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++ - Unexpected exception in std::ifstream

Experimenting with I/O I get an exception where no exception should have been thrown: #include <iostream> #include <fstream> ... 27.5.3.1.1)). 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 pass a method to qsort?

There is a class that contains some data and it sorts them at some point of time. I use qsort() and I'd like ... to do it the right way then? 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++ - Circular Dependencies / Incomplete Types

In C++, I have a problem with circular dependencies / incomplete types. The situation is as follows: ... do to solve 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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c++ - Clang can't compile programs using the <functional> header anymore

I'm using clang Version 4.0.0 on my system running ArchLinux, it always worked fine, but recently I can't compile ... or is my setup messed up? 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++ - Parse ISO 8601 durations

In ISO 8601, durations are given in the format P[n]Y[n]M[n]DT[n]H[n]M[n]S. Examples: 20 seconds: ... similar way without doing a regex by hand? 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++ - program linking fails when using custom built gcc

I'm running a fedora 21 distribution, in which the default gcc is 4.9. I have a custom built gcc/g++ 4.8 ... . What is the problem here ? 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++ - array initialization, is referencing a previous element ok?

const QPointF points[] = { QPointF(r.left() - i, r.top() - i), QPointF(r.right() + i, r ... from the Standard would be highly appreciated. 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 my destructor appear to be called more often than the constructor?

#include<iostream> using namespace std; class A{ public: static int cnt; A() { ++cnt; cout<<"constructor:" ... destructor don't appear in pairs? 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::list::size have constant complexity in C++11?

I am using gcc 4.8.1 and after hours of debugging a horrible mysterious performance issue I found out that ... version of the standard library? 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++ - Can a member of a class be named the same name as its type (another class)?

Trying to compile the following code on different compilers gives me two different results: struct S{}; struct T{S ... actually do this or not? 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++11 functionality with MinGW

I try to use emplace() function for an unordered_map and compiler says that no such function exists. I put - ... C++11 functionality with mingw? 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 Program C++11 Using Qt5?

I'm getting ready to program a cross-platform project with my friend. We decided on using Qt and gcc as our IDE and ... 7-4.8) C++11 in Qt5 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++ - Unexpected results with std::ofstream binary write

I'm new to C++ std::stream and I'm making some tests. I have this simple code: int i = 10; char c = ... you please tell me what I'm 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++ - Qt - 4.7.3 - How to make static build

I used 4.7.2 for the past months. Now I downloaded 4.7.3. Now I am searching to type "configure -static ... anybody shed a light on this issue. See Question&Answers more detail:os...

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

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