Recent questions tagged C++

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I am trying to use mix in classes for C++/Qt to provide a whole bunch of widgets with a common interface. ... that in. Is there another way? 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++ - Braces around string literal in char array declaration valid? (e.g. char s[] = {"Hello World"})

By accident I found that the line char s[] = {"Hello World"}; is properly compiled and seems to be treated the ... My compiler is gcc-4.3.4. 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 enforce the 'override' keyword?

Is there any way to enforce the usage of the C++11 override keyword in Visual C++ 2012? (i.e. if I forget ... I want to get a warning/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++ - QTableView printing

I am new on QT an I try to print out from QTableView How can I do this? Thank a lot 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++ - EnumDisplayDevices vs WMI Win32_DesktopMonitor, how to detect active monitors?

For my current C++ project I need to detect a unique string for every monitor that is connected and active on ... ?) What approach worked best? 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 std::cout have a return value?

I am curious if std::cout has a return value, because when I do this: cout << cout << ""; some hexa ... 's the meaning of this printed value? 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 implementation of random_device in VS2010?

From my reading of the standard, random_device::entropy() should return 0.0 if a software engine is used ... generate the number sequence? 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 enable visual styles without a manifest

According to the docs: "If you want your application to use ComCtl32.dll version 6, you must add an application ... like to use visual styles. 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++ - Cost of throwing C++0x exceptions

What are the performance implications of throwing exceptions in C++0x? How much is this compiler dependent? This ... handling like in Java? 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++ - GCC -Wuninitialized / -Wmaybe-uninitialized issues

I am experiencing a very strange issue using gcc-4.7 (Ubuntu/Linaro 4.7.2-11precise2) 4.7.2. I am unable ... this a compiler bug. Any thoughts? 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 detect whether Windows is shutting down or restarting

I know that when Windows is shutting down, it sends a WM_QUERYENDSESSION message to each application. This makes it ... ceases to amaze 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++ - LTO, Devirtualization, and Virtual Tables

Comparing virtual functions in C++ and virtual tables in C, do compilers in general (and for sufficiently large ... than adding two integers). 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++ - printf rounding behavior for doubles

Can someone explain this behavior? I am well aware of machine-level representation of floating point numbers. This ... one gets rounded up. 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++ - C++11 constexpr function pass parameter

Consider the following code: static constexpr int make_const(const int i){ return i; } void t1(const int i) ... is not a constant expression) } 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++ - When is explicit move needed for a return statement?

In a comment to another question Jonathan Wakely responds to my statement: You never need explicit move for a ... rules or of unique_ptr?? See Question&Answers more detail:os...

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

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336 views

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c++ - Use of typename keyword with typedef and new

Consider this code, template<class T> struct Sample { typename T::X *x; //declare pointer to T's X }; In ... look at it before replying. :-) See Question&Answers more detail:os...

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

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319 views

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c++ - Overload resolution with ref-qualifiers

While working with ref-qualified function overloads, I'm getting different results from GCC (4.8.1) and ... const-qualified rvalue overload. 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++ - Can std::vector emplace_back copy construct from an element of the vector itself?

When using push_back of std::vector, I can push an element of the vector itself without fear of invalidating the ... == 2 before this call? 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 the libc++ std::vector internally keeps three pointers instead of one pointer and two sizes?

I'm looking at the implementation of std::vector in libc++ and I noticed that it internally keeps three pointers ... the "pointer + sizes" one? 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++ - Maximum Stack Size for C/C+ Program?

I've tried the below program. The intent by which this program was created is to discover more about stack sizes. ... it would be very helpful. See Question&Answers more detail:os...

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

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322 views

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c++ - Pointers to virtual member functions. How does it work?

Consider the following C++ code: class A { public: virtual void f()=0; }; int main() { void (A::*f)() ... call B::f. How does it happen? See Question&Answers more detail:os...

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

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383 views

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c++ - C++11 virtual destructors and auto generation of move special functions

The rules for auto generating special move functions (constructor and assignment operator) in C++11 specify that no ... ("client") code? See Question&Answers more detail:os...

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

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310 views

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c++ - What are data breakpoints?

I just came to know that there are data breakpoints. I have worked for the last 5 years in C++ using ... variable value. Any other examples? See Question&Answers more detail:os...

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

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396 views

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c++ - When to use functors over lambdas

Is there ever a situation where it makes more sense to create a functor than to use a lambda? I know my ... a lambda. Any thoughts on 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++ - Convert char array to single int?

Anyone know how to convert a char array to a single int? char hello[5]; hello = "12345"; int myNumber = ... My number is: %d", myNumber); See Question&Answers more detail:os...

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

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420 views

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c++ - What happens if a constructor throws an exception?

Will we get UB then? I tried this: #include <iostream> struct B { B(){ std::cout << "B()" << std:: ... of block scope variables, do we get UB? See Question&Answers more detail:os...

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

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630 views

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c++ - Does std::mutex create a fence?

If I lock a std::mutex will I always get a memory fence? I am unsure if it implies or ... . Multithreaded programming and memory visibility See Question&Answers more detail:os...

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

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343 views

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c++ - Performance difference of "if if" vs "if else if"

I was just thinking is there any performance difference between the 2 statements in C/C++: Case 1: if (p==0) do_this ... ); if(p==2) do_these(); See Question&Answers more detail:os...

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

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