Yes, per [string.accessors] p1, std::basic_string::c_str(): Returns: A pointer p such that p + i == &operator[](i) for each i in [0,size()]. Complexity: constant time. Requires: The program shall not alter any of the values stored in the character array. This means that given a string s, the pointer returned by s.c_str() must be the same … Read more
It can only be done for aggregates (arrays and certain classes. Contrary to popular belief, this works for many nonpods too). Writing a constructor that takes them is not possible. Since you tagged it as “C++0x”, then this is possible though. The magic words is “initializer-list constructor”. This goes like Phenotype(std::initializer_list<uint8> c) { assert(c.size() <= … Read more
It will call delete[] and hence the entire array will be reclaimed but I believe you need to indicate that you are using an array form of unique_ptrby: std::unique_ptr<int[]> my_array(new int[5]); This is called as Partial Specialization of the unique_ptr.
No. Returns: Each function returns a string object holding the character representation of the value of its argument that would be generated by calling sprintf(buf, fmt, val) with a format specifier of “%d”, “%u”, “%ld”, “%lu”, “%lld”, “%llu”, “%f”, “%f”, or “%Lf”, respectively, where buf designates an internal character buffer of sufficient size.
As of C++20, yes, but only if the std::string is destroyed by the end of constant evaluation. So while your example will still not compile, something like this will: constexpr std::size_t n = std::string(“hello, world”).size(); However, as of C++17, you can use string_view: constexpr std::string_view sv = “hello, world”; A string_view is a string-like object … Read more
How can I do what I want to do (that is, initialize an array in a constructor (not assigning elements in the body)). Is it even possible? Yes. It’s using a struct that contains an array. You say you already know about that, but then I don’t understand the question. That way, you do initialize … Read more
We start with the move function (which I cleaned up a little bit): template <typename T> typename remove_reference<T>::type&& move(T&& arg) { return static_cast<typename remove_reference<T>::type&&>(arg); } Let’s start with the easier part – that is, when the function is called with rvalue: Object a = std::move(Object()); // Object() is temporary, which is prvalue and our move … Read more
As others have pointed out, you’ve got it figured out correctly regarding your original 3 questions. But the ending part of your edit Calling reset() in thread IV will delete previous instance of A class created in first thread and replace it with new instance? Moreover after calling reset() in IV thread other threads will … Read more
is there some other clause in the language specification that this exploits? Yes, see 12.8 §34 and §35: When certain criteria are met, an implementation is allowed to omit the copy/move construction of a class object […] This elision of copy/move operations, called copy elision, is permitted […] in a return statement in a function … Read more
With C++17, shared_ptr can be used to manage a dynamically allocated array. The shared_ptr template argument in this case must be T[N] or T[]. So you may write shared_ptr<int[]> sp(new int[10]); From n4659, [util.smartptr.shared.const] template<class Y> explicit shared_ptr(Y* p); Requires: Y shall be a complete type. The expression delete[] p, when T is an array … Read more