Recent questions tagged c++

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c++ - Is left-shifting a signed integer undefined behavior in C++03?

According to C++03, 5.8/2, left-shifting is defined as follows: The value of E1 << E2 is E1 (interpreted ... a signed integer defined in C++03? 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 sizeof(size_t) == sizeof(void*) always true?

Does the C99/C++11 standard guarantee that sizeof(size_t) == sizeof(void*) is always true? size_t f(void* p) { return ... (n); // Is it safe? } 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 std::vector<bool> have no .data()?

The specialisation of std::vector<bool>, as specified in C++11 23.3.7/1, doesn't declare a data() member ... an array of bools not be returned? 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++ - Template specialization with variadic templates

template <size_t size, typename ...Params> void doStuff(Params...) { } template <> void doStuff<size_t ... How to specialize variadic templates? 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++ - Weird GCC array initialization behavior

I encountered a variant of this code when looking at another question (the original code used a std::thread instead of ... or just a plain 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++ - What is the "interface" keyword in MSVC?

I'm looking through the Windows 8.1 SDK and in UnknownBase.h I'm seeing things like typedef interface IUnknown ... anyone clue me in 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++ - Is it allowed to call destructor explicitly followed by placement new on a variable with fixed lifetime?

I know that calling destructor explicitly can lead to undefined behavior because of double destructor calling, like ... have any const members. 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++ - Declaration of method changes meaning of symbol

For the following code: struct foo {}; struct A { typedef foo foo_type; void foo(); }; GCC gives a compiler ... gcc and clang accept the code. 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++ - Behaviour of std::list:begin() when list is empty

Does the following give defined results in terms of the C++ standard? std::list<int> myList; std::list<int> ... d like a more definitive answer. 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 a vector of pointers not castable to a const vector of const pointers?

The type vector<char *> is not convertible to const vector<const char*>. For example, the following gives a compilation ... by the C++ FQA 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++ - Modifying a data structure while iterating over it

What happens when you add elements to a data structure such as a vector while iterating over it. Can I not do this? I tried ... j << " .. "; } } 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 reverse function for strstr

I am trying to find a similar function to strstr that searches a substring starting from the end towards the beginning of the string. 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 operator% referred to as the "modulus" operator instead of the "remainder" operator?

Today at work I had an interesting discussion with one of my coworkers. He was surprised when he had ... modulus operator truncates toward 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++ - Using an std::string as a key for an std::map

I would like to have an std::map (int .NET 4.0). We of course know that a map is a tree and ... this is: CustomObject o = stringObjectMap[key]; 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++ - Forcing auto to be a reference type in a range for loop

Suppose I have foo which is a populated std::vector<double>. I need to operate on the elements of this ... I'm missing some trivial syntax. 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 storage for the same content string literals guaranteed to be the same?

Is the code below safe? It might be tempting to write code akin to this: #include <map> const std::map< ... translation units. Am I right? 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 with RTTI disabled

I'm curious to know what happens when compiling code with a dynamic cast whith RTTI disabled (either with -fno-rttion GCC ... *>(myA))->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++ - Why does tm_sec range from 0-60 instead of 0-59 in time.h?

My time.h has the following definition of tm: struct tm { int tm_sec; /* seconds after the minute [0-60] */ ... going on that I'm unaware of? 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 `CString`?

Why do I see some code using CStrings declared differently. Some use this format char a_c_string []; While ... people are giving examples. 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++ - constexpr begin of a std::array

I am having trouble understanding why both gcc-8.2.0 and clang-7.0.0 reject the following code (live code ... . Is this a compiler 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++ - Complexity of std::list::splice and other list containers

I have some code which deals with various std::list objects, and I am currently using a very inefficient ... complexity would be quite valuable. 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 you insert with a reverse_iterator

I want to insert something into a STL list in C++, but I only have a reverse iterator. What is the usual way ... (); l.insert(reverse, 10); 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++ - QtCreator CMake project - how to show all project files

I use QtCreator to open CMake project. Some directories apart from CMakeLists.txt contains only headers files ... project files from QtCreator. 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 undefined behaviour to delete a null void* pointer?

I know that deleteing a null pointer is a no-op: In either alternative, if the value of the operand of delete is ... p; // UB or well-defined? 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::sort work with lambda function in c++0x/c++11?

I tried to use lambda function with sort, but was getting "Segmentation fault" errors. I managed to simplify ... with "Segmentation fault". 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 Unrecognised instruction

I have the following code: #include <iostream> #include <random> int main() { std::mt19937_64 rng(std:: ... valgrind to profile my code? 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 virtual functions use return type deduction?

n3797 says: § 7.1.6.4/14: A function declared with a return type that uses a placeholder type shall not ... that agrees with the above quote? 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 C1047: Object file created with an older compiler than other objects

I have a project that I'm building in C++ in Release mode in Visual Studio 2008 SP1 on Windows 7 and when I ... also didn't fix it. 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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