Recent questions tagged C++

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c++ - Should preprocessor instructions be on the beginning of a line?

A while ago I have discovered an (rather ancient) C Compiler, which scanned macros this way (Pseudo code): if ... will always work the same 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++ - Locking multiple mutexes

I'm wondering if it's possible to lock multiple mutexes at the same time, like: Mutex1.Lock(); { Mutex2 ... useful for some situations. 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++ - Generating an error if checked boolean macro is not defined

I have several configuration files each one containing the definition of some boolean macro, to be set to 0 or ... of the header defining FOO. 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++ - Static map initialization

I have the following code: //MyClass.h class MyClass { public: typedef std::map<std::string, int> OpMap ... I (statically) initialize opMap_? 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't variables defined in a conditional be constructed with arguments?

The question is simple. Why does this compile: bool b(true); if (b) { /* */ } And this compile: if ... what non-ugly workarounds there may 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++ - How to extend std::tr1::hash for custom types?

How do I allow the STL implementation to pick up my custom types? On MSVC, there is a class std:: ... similar for the TR1 implementation? 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 final classes

I was reading comments on Herb Sutter's Guru of the Week redux about virtual functions, and finally saw ... obscure and almost unused feature? 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# generic with constant

Is there something similar to this C++ template? template <int A> class B { int f() { return A; } } I ... , etc (eg tuple) a different 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++ - At least one module has an unresolved import due to a missing export function in an implicitly dependent module

When I point to my C++ dll from DependencyWalker, I see the error message "At least one module has an ... please suggest what the error is? 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++ - volatile struct = struct not possible, why?

struct FOO{ int a; int b; int c; }; volatile struct FOO foo; int main(void) { foo.a = 10; foo ... a default copy constructor from a volatile? See Question&Answers more detail:os...

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

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265 views

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c++ - Can a class share a namespace's name?

Is the following C++ code valid? namespace Foo { class Bar { // Class code here. }; } namespace Foo { ... with the same name as a 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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c++ - Differentiate String Literal from Char Array

I want to write some function that takes a string literal - and only a string literal: template <size_t N> ... any compiler would be great). 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 is the difference between is_convertible is_assignable

What is the difference between is_convertible and is_assignable? Why, in vs2012 is_convertible<int, int&> is false ... , int&> is false See Question&Answers more detail:os...

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

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485 views

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c++ - Override number of parameters of pure virtual functions

I have implemented the following interface: template <typename T> class Variable { public: Variable (T v) : m_value (v ... there a way to do it? See Question&Answers more detail:os...

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

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305 views

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c++ - How do I check my template class is of a specific classtype?

In my template-ized function, I'm trying to check the type T is of a specific type. How would I do that? p/ ... of type, say, String? } 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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464 views

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c++ - Why can creating a static const std::string cause an exception?

I have string constants, for strings that I use in multiple places in my app: namespace Common{ static ... above, risks throwing exceptions ? See Question&Answers more detail:os...

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

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328 views

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c++ - how to find the "true" entropy of std::random_device?

I want to check whether my implementation of std::random_device has non-zero entropy (i.e. is non- ... . using heat dissipation monitors? See Question&Answers more detail:os...

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

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219 views

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c++ - Is numeric_limits<int>::is_modulo logically contradictory?

In another question, the topic of std::numeric_limits<int>::is_modulo came up. But the more I think about ... ? Am I missing something? See Question&Answers more detail:os...

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

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219 views

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c++ - How to insert into std::map?

Is there a std iterator I could use to insert elements into std::map using a std algorithm (for example std:: ... - items needs to be sorted. See Question&Answers more detail:os...

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

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479 views

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c++ - Using std::visit on a class inheriting from std::variant - libstdc++ vs libc++

Consider the following code snippet: struct v : std::variant<int, std::vector<v>> { }; int main() { ... implementation is correct here, and 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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298 views

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c++ - Use of constexpr function before definition fails

I'm having some trouble with constexpr. The book C++ Primer shows a line of code: constexpr int sz = size(); ... well. Can someone tell me 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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365 views

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c++ - Why does "most important const" have to be const?

In http://herbsutter.com/2008/01/01/gotw-88-a-candidate-for-the-most-important-const/ it mentions "most important ... does it have to be 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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1.2k views

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c++ - Should I preallocate std::stringstream?

I use std::stringstream extensively to construct strings and error messages in my application. The stringstreams are ... more elegant method?) 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 explicitly call a conversion function whose conversion-type-id contains a placeholder specifier

struct A{ operator auto(){ return 0; } }; int main(){ A a; a.operator auto(); // #1 a. ... function when it contains a placeholder specifier? 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++ - In C++11 and beyond does std::string::operator[] do bounds checking?

I have seen many times that std::string::operator[] does not do any bounds checking. Even What is the ... now required to do bounds checking? See Question&Answers more detail:os...

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

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255 views

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c++ - Is it okay to use "and", "or" etc. instead of "&&", "||"?

I'm used to the and and or keywords in C++. I've always used them and typing them is fast and comfortable for ... P.S.I use the MinGW compiler. See Question&Answers more detail:os...

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

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571 views

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c++ - Why isn't atomic double fully implemented

My question is quite simple. Why isn't std::atomic<double> implemented completely? I know it has to do with ... on most C++ implementations. See Question&Answers more detail:os...

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

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395 views

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c++ - Why use std::less as the default functor to compare keys in std::map and std::set?

I am wondering why std::map and std::set use std::less as the default functor to compare keys. Why not ... the default functor to compare keys? See Question&Answers more detail:os...

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

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