Recent questions tagged C++

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c++ - Multiple inheritance with qobject base

Example of code: class TestOne : public QWidget // To fix this i need to modify class QWidget : public virtual ... to get around 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++ - gcc: warning: large integer implicitly truncated to unsigned type

#include<stdio.h> int main() { unsigned char c; c = 300; printf("%d",c); return 0; } Is the output in any way predictable or its undefined?? 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++ - ZMQ poll not working

When I run the following code, I get an error on the first call to zmq_poll (i.e. it returns -1). The ... message = "Unknown 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++ - Why would you write something like this? (intentionally not using delete [] on an array)

I came across this kind of code once in a while - I suspect the creator is/was afraid that table delete would ... table; // no [] intentionally 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++ - Construction of temporary in function call is interpreted as declaration

Lately I ran into a problem which somehow (but only somehow) makes sense to me. It is based on interpreting ... but about redefinition of x. 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 parameter of a template template parameter cause shadowing?

Is this legal C++? template <typename T, template <typename T> class> struct S { }; Clang (3.7.1) rejects ... //goo.gl/51bHVG (gcc.godbolt.org) 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 make Valgrind log all allocations?

I'd like to make Valgrind log the allocations even when no memory errors were found. How can this 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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c++ - Determining Qt stylesheet options programmatically?

Is it possible to look up stylesheet values at runtime in Qt? I'm working on a custom button derived from ... parsing out the values myself? 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 mersenne twister thread safe for cpp

#include <random> int f() { std::random_device seeder; std::mt19937 engine(seeder()); std::uniform_int_distribution< ... seeder()); every time? 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 a constexpr static member of a reference as template argument

I'm trying to figure out whether GCC or Clang interpret the C++17 standard differently / wrong here. This is ... -pedantic) be considered a bug? 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++ - Getting fault address that generated a UNIX signal

I am interested in a signal handler which can identify the address of the instruction which caused the problem. I know ... .0.9.Elsmp and SunOS. 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 read a specific amount of characters from a text file

I tried to do it like this #include <iostream> #include <fstream> using namespace std; int main() { char b[2]; ... work in C++ for some reason. 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++ __FUNCTION__ replace time

Can anyone tell when g++ replaces the __FUNCTION__ 'macro' with the string containing the function name? It ... variable in the compiled code? 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++ - Expanding parameter pack into lambda with fold expression - gcc vs clang

Considering the following code snippet: template <typename TF> void post(TF){ } template <typename... TFs> struct funcs ... is this a gcc bug? 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++ - I'm getting an error concerning enum (I think)

I'm testing code remotely on a Solaris machine through SSH Secure Shell using c++. Not sure of what ... issue would be GREATLY 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++ - When all does comma operator not act as a comma operator?

If you see this code, class A{ public: A(int a):var(a){} int var; }; int f(A obj) { return obj. ... a comma operator? Or the other way around? 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 linkage for function pointer passed to C library

My case is pretty simple: I want my C++ program to deal with Unix signals. To do so, glibc provides ... : can uponSignal be declared static? 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++ - Prevent C++11 removal of endless loops

As discussed in this question, C++11 optimizes endless loops away. However, in embedded devices which ... disabling optimization altogether? 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 it be safe to keep a copy of an std::initializer_list? What is the rationale?

In my environment, the std::initializer_list is implemented as a pointer to the first element, and a size. ... of "least astonishment") 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++ - Printing char by integer qualifier

I am trying to execute the below program. #?include? "stdio.h" #include "string.h" void main() { char c ... answer is 56. Can somebody explain ? 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 constructor inheritance and constructors with no parameters

In this piece of code, why is A's constructor with no parameters not inherited? Is there a special rule that prevents ... from here A(void *) {} 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++ - Compilation fails with OpenMP on Mac OS X Lion (memcpy and SSE intrinsics)

I have stumbled upon the following problem. The below code snippet does not link on Mac OS X with any ... D_FORTIFY_SOURCE=0 flag eventually do? 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 `double` guaranteed by C++03 to represent small integers exactly?

Does the C++03 standard guarantee that sufficiently small non-zero integers are represented exactly in double? If not ... help me unpack 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++ - Clang, std::shared_ptr and std::less/operator<

Having the following code #include <memory> int main() { std::shared_ptr<int> ptr0( new int ); std:: ... work for shared pointers 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++ - BitBlt ignores CAPTUREBLT and seems to always capture a cached copy of the target

I am trying to capture screenshots using the BitBlt function. However, every single time I capture a screenshot, ... nothing works. Any ideas? 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 locals destroyed before or after evaluation of a function return value?

I am thinking of making a class which represents ownership of a synchronization primitive, something like this: class ... hard-to-find 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++ - How do you get the type of a member function

The question is inspired by a note in the standard [class.mem] The type of a non-static member function is ... standard is irrelevant to 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++ - braced-init-list and unsigned types

gcc 8 and clang 7 do not accept the following code, which should default-construct a temporary of type ... suffer from the same restriction? See Question&Answers more detail:os...

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

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