Recent questions tagged C++

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c++ - Qt GUI Development - Displaying a 2D grid using QGraphicsView

I'm new to Qt development so I've being trying to research a solution to a user interface I need to design ... be much appreciated. Thanks, Dan 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 Struct Stat()

I'm trying to figure out how exactly to use stat() to capture information about a file. What I need is ... the returned information from stat()? 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 type const double is not captured by lambda from reaching-scope, but const int is?

I seem can't understand why the following code with type const int compiles: int main() { using T = int; ... to refer to reaching-scope name? 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 `mysql_init'

I am trying to compile my program on my new server, but it's not working for me at the moment. Error ... libs` See answer below for explanation. 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 aliasing rules and memcpy

While answering another question, I thought of the following example: void *p; unsigned x = 17; assert( ... without breaking the aliasing rules? 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 use BOOST_FOREACH with a boost::ptr_map?

How can I use BOOST_FOREACH efficiently (number-of-character/readability-wise) with a boost::ptr_map? Kristo demonstrated in ... i = p.first; } 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 happens when you assign a literal constant to an rvalue reference?

This is admittedly a nit-picky question that is mainly driven by curiosity. Suppose we have the following: int x ... could be bound to rvalues. 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 divide 16-bit integer by 255 with using SSE?

I deal with image processing. I need to divide 16-bit integer SSE vector by 255. I can't use shift ... might somebody knows another 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++ - Do classes have external linkage?

I have 2 files A.cpp and B.cpp which look something like A.cpp ---------- class w { public: w ... internal linkage. Am I missing something here? 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 __attribute__((packed)) affect the performance of a program?

I have a structure called log that has 13 chars in it. after doing a sizeof(log) I see that the size is ... is error prone. Have any suggestion? 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's the fastest stride-3 gather instruction sequence?

The question: What is the most efficient sequence to generate a stride-3 gather of 32-bit elements from memory? ... only discuss the first case. 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 boost::thread_group execute a fixed number of parallel threads

This is the code to create a thread_group and execute all threads in parallel: boost::thread_group group; for (int ... are no more to execute. 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++ treats returned string literal as const char pointer not const char array

I'm seeing some odd behaviour when returning a string literal from a function that should perform an implicit ... - could anyone confirm? 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++ - dynamic_cast fails when used with dlopen/dlsym

Intro Let me apologise upfront for the long question. It is as short as I could make it, which is, ... Ubuntu 9.10) Example code available See Question&Answers more detail:os...

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

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367 views

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c++ - Version resource in DLL not visible with right-click

I'm trying to do something which is very easy to do in the regular MSVC, but not supported easily in VC++ ... "Translation", 0x409, 1200 END END See Question&Answers more detail:os...

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

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191 views

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c++ - Load multiple copies of a shared library

I am running Linux, and I would like to be able to make parallel function calls into a shared library (.so) ... , each with a different name) 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++ - Initializer list *argument* evaluation order

So, the C++ standard requires that class members be initialized in the order in which they are declared ... allocation sometimes can be. 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 exactly is a namespace and why is it necessary

I am learning C++ right now, and at the beginning of every project my instructor puts a line that says: ... paradigm is very confusing for me. 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 are the differences between #pragma pack(push, n)/#pragma pack(pop) and __attribute__((__packed__, aligned(n) )) on GCC?

On GCC specifically (that is, compiling both with GCC), what are the differences between the way the following two ... the same, at least? 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 Visual Studio 2017 need an explicit move constructor declaration?

The below code can be compiled successfully using Visual Studio 2015, but it failed using Visual Studio 2017. Visual ... . What is the 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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310 views

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c++ - Create std::string from std::istreambuf_iterator, strange syntax quirk

I found somewhere the following idiom for reading a file into a string: std::ifstream file("path/to/some/file.ext"); std ... am using g++ 4.8.2. 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++ - Pointer to member conversion

I just found the following paragraphs in c++03 standard draft relevant to pointer to member conversion. 4.11/2 ... to member of derived class. See Question&Answers more detail:os...

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

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303 views

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c++ - Static templated constexpr nested class member

I have the following sample class Foo with nested class Bar and everything is constexpr: class Foo { private: template ... into what's going on) 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 specialization of function templates causes linker error

Functions.h: #pragma once #include <iostream> template<class T> void TemplatedFunction(T* p) {} template<> void ... if they are not used? 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++ - "ambiguous overload for 'operator[]'" if conversion operator to int exist

I'm trying to implement the vector like and the map like [] operator for a class. But I get error messages ... 'size_t {aka long unsigned int}' 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++ - "lib" Prefix on Libraries

From http://www.adp-gmbh.ch/cpp/gcc/create_lib.html: Note: the library must start with the three letters lib ... . What's it doing differently? See Question&Answers more detail:os...

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

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156 views

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c++ - Is unit testing private methods a good practice?

I am wondering if unit testing private methods is a good practice? Normally only public interface should be tested. ... so is good practice. See Question&Answers more detail:os...

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

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124 views

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c++ - How do I safely and sensibly determine whether a pointer points somewhere into a specified buffer?

I'm looking to implement a function that determines whether a given pointer points into a given buffer. The ... is determined in constant 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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