Recent questions tagged C++

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c++ - Cannot evaluate function -- may be inlined

I wrote a function similar to this: class abc { private : int m_var ; public : int func() { return ... print values from an inlined function? 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 int i=400*400/400 gives result 72, is datatype circular?

I think first 400*400=160000 is converted to 28928 by starting from 0 and going 160000 time in a circular ... there is any other 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++ - How can I get sizeof a vector::value_type?

I want to get sizeof of the type that is contained in a vector. Here is what I tried: #include <iostream> ... the size of the contained type? 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++ class template specialization, without having to reimplement everything

I have a templatized class like so : template<typename T> class A { protected: std::vector<T> ... other already existing methods? 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++ - Why does my translation matrix needs to be transposed?

I'm working on a small graphics engine using OpenGL and I'm having some issues with my translation matrix. I'm ... .data is a std::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 to declare constexpr C string?

I think i quite understand how to use the keyword constexpr for simple variable types, but i'm confused when ... "; or something yet different? 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++ - Use cases for std::add_const and similar

Some type transformations in <type_traits> can also be expressed using core language syntax (e.g. std::add_const< ... the occasional meta-use? 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 the fractional part of a float without using modf()

I'm developing for a platform without a math library, so I need to build my own tools. My current way ... fp_amount_inv; } 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++ - How can I create a HTTP POST request with Qt 4.6.1?

How can I create a HTTP POST request with some URL encoded parameters using Qt 4.6.1? I figured out that I ... (request,data); return reply; } 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 message: "setw is not defined" using g++

I am trying to compile using gcc a project which earlier used SunStudio and am getting an error in the ... me reason behind this 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++ - Crash with icc: can the compiler invent writes where none existed in the abstract machine?

Consider the following simple program: #include <cstring> #include <cstdio> #include <cstdlib> void replace(char ... entirely self-contained. 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++ - Capturing reference variable by copy in C++0x lambda

According to the answers and comments for this question, when a reference variable is captured by value, the lambda ... and more like 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++ - How should I handle "cast from ‘void*’ to ‘int’ loses precision" when compiling 32-bit code on 64-bit machine?

I have a package that compiles and works fine on a 32-bit machine. I am now trying to get it to compile ... these files to avoid these casts? 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++ - Rule of thumb for when passing by value is faster than passing by const reference?

Suppose I have a function that takes an argument of type T. It does not mutate it, so I have the choice of ... to be "very cheap to copy"? 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 pointer arithmetic without object of structure

I think it is not possible in C but ask to verify this. Is it possible to make arithmetic between structure ... the case is interesting 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++ - How to declare an __stdcall function pointer

I tried this typedef void (* __stdcall MessageHandler)(const Task*); This compiles but gives me this warning (VS2003 ... What am I 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++ - How to call std::min() when min has been defined as a macro?

How do I call std::min when min has already been defined as a macro? 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 I tell valgrind to memcheck forked processes?

I have a process x that I want to check for leaks with valgrind. The problem is that x is run by y, and y ... linux and valgrind-2.4.0. 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++ - Why can const members be modified in a constructor?

I'm curious why const members can be modified in the constructor. Is there any standard rule in initialization that ... be an error 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++ - Calling a static method by repeating the object name?

I have a singleton: struct foo { static foo& instance() { static foo f; return f; } }; When re-arranging ... ::foo::instance() compiles. Why? 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++ - Create string with specified number of characters

Is there a way to create a string of say 256 characters at initialization with c++? Part of my assignment ... like there is an easier way. 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++ - Valgrind reporting a segment overflow

When running my program with valgrind / callgrind I get the following message a lot: ==21734== brk segment ... valgrind, or of my program? 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 does the gcc warning "project parameter passing for X changed in GCC 7.1" mean?

I have a C++ project that builds fine and without warnings with gcc 7.2 on x86 Linux and Windows, I needed to ... of what they mean.. any clue? 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 implicit conversion in constructor. The 'explicit' keyword doesn't help here

I am able to avoid the implicit conversion of a constructor using the explicit keyword. So now, conversions like A a1 = ... a1.num; 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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c++ - Does new char actually guarantee aligned memory for a class type?

Is allocating a buffer via new char[sizeof(T)] guaranteed to allocate memory which is properly aligned for the type ... is an over-aligned type? 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++ - Redefining lambdas not allowed in C++11, why?

Example: #include <functional> int main() { auto test = []{}; test = []{}; return 0; } This ... to be omitted for lambdas generally. 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 point of const void?

Apparently, it is possible to declare a function returning const void: const void foo() { } g++ seems ... void have any practical significance? 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 alphabetically sort strings?

I have been trying to use this c++ program to sort 5 names alphabetically: #include <iostream> #include < ... whats wrong with my program? See Question&Answers more detail:os...

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

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