Recent questions tagged C++

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c++ - Bison : Line number included in the error messages

OK, so I suppose my question is quite self-explanatory. I'm currently building a parser in Bison, and I want to ... how this is to be 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++ - GDB shows incorrect arguments of functions for stack frames

Whenever GDB steps in functions, instead of showing correct arguments in frame info, it prints garbage data ... correct arguments of functions? 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++ - Atomically clearing lowest non-zero bit of an unsigned integer

Question: I'm looking for the best way to clear the lowest non-zero bit of a unsigned atomic like std:: ... you can show me one). 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++ - Problems converting YV12 to RGB through GLSL

I'm trying to accomplish YV12 to RGB conversion mentioned in this post with GLSL shaders. My application loads a ... (); 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++ - Avoid the most vexing parse

How do I get the compiler to create temporaries, use the default constructor on them while not defining a function? ... T1& t1) not called } 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 SFINAE out non-containers parameters

I have a template function that I want to enable only for standard containers (or containers compatible with standard ... is lacking begin(). 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 non-indirection, non-hack way to guarantee that a constexpr function only be callable at compile time?

At the moment, we have two primary options for compile-time evaluation: template metaprogramming (generally using template ... ... yeah, no. 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 refer to std::sin(const valarray<double> &)?

I'm having trouble with some valarray function pointer code: double (*fp)(double) = sin; valarray<double> (* ... class std::valarray<double>&)' 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++ - vector serialization

I am trying to binary serialize the data of vector. In this sample below I serialize to a string, and then deserialize back ... 0 (on gcc-4.5.1) 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++ - Technique for using std::ifstream, std::ofstream in python via SWIG?

Is there a way to use std::[io]fstream's in python via swig? I have a c-class with functions like: void ... making the file streams that I need. 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 is mktime() changing the year day of my tm struct?

I read in two strings with a Year, the Julian Day (year day), hour, minute, and an observation. I pull the ... and not the month and month day? 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 deduce the value of a function pointer template parameter?

C++ allows non-type template parameters to be of pointer, including function pointer, type. I recently asked a ... that makes more sense now. 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 copy constructor and assignment operator are disallowed?

#undef GOOGLE_DISALLOW_EVIL_CONSTRUCTORS #define GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeName) TypeName(const TypeName&); void operator= ... ? 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 not modify key of associative container?

I know that it's a terrible idea to change the key of an object in an associative container, but I wonder ... hiding in a future defect report? 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++ - overloading "<<" with a struct (no class) cout style

I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible ... I cant seem to make it work. 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 is new int (*)[3] an error?

typedef int (*A)[3]; int (**p)[3] = new A; // OK int (**q)[3] = new (int(*)[3]) ... . Why are the extra parentheses required in this expression? 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++ - Suppress warning "QApplication was not created in main() thread"

I've created a Qt-based network library for use with applications that are not running a Qt event loop, and ... ideas to suppress the warning. 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 print out dash or dot using fprintf/printf?

As of now I'm using below line to print with out dot's fprintf( stdout, "%-40s[%d]", tag, data); ... out dash or dot using fprintf/printf? 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++ - Transferring data through a memory-mapped file using Win32/WINAPI

I need to transfer some data - char buffer[100000]; - to a child process which is started by me. Right now ... to save me some effort :) 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 symbols of a shared library are not resolved at link time?

This is my 2nd post on this site in my effort to understand the compilation/linking process with gcc. When ... not undesirable? Thanks, Jagrati 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++ - Reading a video with openCV

I have a video engine2.avi that I want to read and show with openCV. Here's my code: #include <opencv2/core/core. ... waitKey(33); } 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++ - How do I tell Android Studio to use GCC 4.9 with CMake?

I'm using NDK r12 with Android Studio 2.2. I need CMake to use GCC 4.9 instead of Clang to build our ... get CMake to use GCC ARM toolchain? 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 member functions be "const" if they affect logical state, but not bitwise state?

I'm writing a class that wraps a legacy C API that controls a hardware device. In a simplified example, I might ... very much does have state.) 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 it OK to discard placement new return value when initializing objects

This question originates from the comment section in this thread, and has also got an answer there. However, I ... to ignore the return 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++ - force key type of a std::map not to be const

C++ references tells us for a std::map typedef pair<const Key, T> value_type; Is it possible to force the Key Type ... because x is const ... } 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::vector honour alignof(value_type)?

If I define a simple type with a certain alignment requirement, shouldn't a std::vector<t> of said type ... are suitable answers to this one. 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++ - OpenCV Mat::operator= - does it support copy on write?

From the OpenCV documentation, it appears that copying a matrix is done using a shallow copy, but when changing one of ... == 2, intead of 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++ - Trouble with boost::lockfree::queue in shared memory (boost 1.53, gcc 4.7.2 / clang 3.0-6ubuntu3)

I have a problem with placing boost::lockfree::queue<<T, fixed_sized<false>, ..> in shared memory. I need it ... Please tell me what I'm missing See Question&Answers more detail:os...

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

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