Recent questions tagged C++

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c++ - Disabling "bad function cast" warning

I'm receiving the following warning: warning: converting from 'void (MyClass::*)(byte)' to 'void (*)(byte)' ... way to pass a member 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++ - Nested data member pointer - not possible?

The following reduced code sample does not do anything useful but two subsequent assignments to a data member pointer ... Thanks for your 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++ - Get mouse coordinates in QChartView's axis system

Is there a way to get mouse's coordinates on plotting area of a QChartView? Preferably in the axis units. ... this object's coordinate system. 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++17 `filesystem` is not a namespace-name

I am wondering why in the following code, the namespace filesystem is not found: g++ -std=c++17 main.cpp -lstdc++ ... 5.4.0-6ubuntu1~16.04.5) 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 'SDL_main'

I've recently decided to try working with SDL with CodeBlocks 10.05. I started with the tutorial on http:// ... ); }; #endif // CAPP_H_INCLUDED 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++ - Float addition promoted to double?

I had a small WTF moment this morning. Ths WTF can be summarized with this: float x = 0.2f; float y = ... which I think hasn't been mentioned. 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++ - 'wchar.h' file not found

I know about this question: macOS 'wchar.h' File Not Found but it did not help me. I've tried ... it in some completely unrelated folder. 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 pointer arithmetic on inactive member of a union UB?

Let's consider this example code: struct sso { union { struct { char* ptr; char size_r[8]; } ... following question clearly showes my intent 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++ - Implicit cast of null pointer to bool

Suppose I have Foo* foo = nullptr; If I'm checking whether or not foo is nullptr, am I permitted to write if (! ... I write if (foo == nullptr) 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++ - Passing std::filesystem::path to a function segfaults

When I attempt to use std::filesystem::path as a function argument, it segfaults on my machine. Here is a minimal ... be a bug in libstdc++ See Question&Answers more detail:os...

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

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356 views

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c++ - What's the point of "boost::mpl::identity<T>::type" here?

I was checking the implementation of clamp in boost: template<typename T, typename Pred> T const & clamp ( T ... T>::type equivalent to T? 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++ - Which COM smart pointer classes to use?

I'm confused by the choices for COM smart pointers classes for C++ programming: There's three four I'm aware ... COM interface via a TLB file. See Question&Answers more detail:os...

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

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225 views

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c++ - What is my best approach to determining compiler behaviour for empty infinite loops?

An infinite loop with an empty body has undefined behaviour in C++11. I don't know whether it also does ... avoid surprises as much as possible. See Question&Answers more detail:os...

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

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491 views

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c++ - gcc over-aligned new support (alignas )

I'm having some difficulty finding more information about GCC's aligned-new warning and the gcc -faligned-new ... on this is extremely lacking. See Question&Answers more detail:os...

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

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202 views

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c++ - how to prevent numbers from showing up in scientific notations

We have a StreamBuffer class in which we haven't implemented std::fixed operations and I am trying to ... other optimized and efficient 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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272 views

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c++ - Why is ranges::ostream_iterator default-constructible?

This question follows a discussion in the comments here. In Eric Niebler's ranges-v3 library (which is sort-of becoming ... So, what's the deal? 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 an __m128i variable zero?

How do I test if a __m128i variable has any nonzero value on SSE-2-and-earlier processors? See Question&Answers more detail:os...

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

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361 views

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c++ - Replace auto keyword with deduced type (clang or VS2010)

Has anyone written a script, plugin, or executable that replaces each instance of 'auto' with the compiler-deduced type ... ::iterator to '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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454 views

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c++ - std::unordered_map<T,std::unique_ptr<U>> copyable? GCC bug?

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

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184 views

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c++ - Why is the template specialization not chosen?

I wrote the following code: #include <iostream> #include <string> #include <type_traits> template<typename, typename = void ... 0 1. 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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217 views

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c++ - What happens if a throw; statement is executed outside of catch block?

In C++ throw; when executed inside a catch block rethrows the currently caught exception outside the block. ... behaviour for such situations? See Question&Answers more detail:os...

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

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148 views

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c++ - May I initialize a global variable with the result of a function call?

Is the following code legal? int add(int a, int b) { return a + b; } int myvar = add(1, 2); int main() { /* ... */ } Why, or why not? See Question&Answers more detail:os...

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

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361 views

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c++ - in bitset, can i use "to_ulong" for a specific range of bits?

I'm working on something that requires me to get access to specific bits and ranges of bits. I decided to use ... a range (subset) of bits? See Question&Answers more detail:os...

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

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409 views

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c++ - Trying to assign vector of Base* from vector of Derived*

This seems like a pretty basic problem, but I can't figure it out. I have a std::vector of raw pointers to ... Seems like the same thing to 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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159 views

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c++ - Usage of "this" in destructor

Is it valid to call some function in destructor with this argument? Function does not store pointer, but assume full-functional object. See Question&Answers more detail:os...

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

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181 views

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c++ - Overload C macros

Is there a better way to "overload" a macro like this? I need a macro that accepts various numbers of ... DEBUG_TRACE_2("more", "params"); See Question&Answers more detail:os...

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

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392 views

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c++ - Why in g++ std::intmax_t is not a __int128_t?

My question is pretty simple: as std::intmax_t is defined as the maximum width integer type according to cppreference ... to __int128_t in GCC? See Question&Answers more detail:os...

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

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500 views

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c++ - No matching function for QObject::connect

I'm writing a program that send an UDP frame every 10 mS. Here's how my program is supposed to work ... function. What should I change? See Question&Answers more detail:os...

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

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