There appears to be a related bug report, Bug 59659 – large zero-initialized std::array compile time excessive. It was considered “fixed” for 4.9.0, so I consider this testcase either a regression or an edgecase not covered by the patch. For what it’s worth, two of the bug report’s test cases1, 2 exhibit symptoms for me … Read more
The usual. template<size_t…Is> std::array<foo_t, sizeof…(Is)> make_foos(std::index_sequence<Is…>) { return { ((void)Is, make_foo())… }; } template<size_t N> std::array<foo_t, N> make_foos() { return make_foos(std::make_index_sequence<N>()); }
There is currently no way to do this without rolling your own make_array, there is a proposal for this N3824: make_array which has the following scope: LWG 851 intended to provide a replacement syntax to array<T, N> a = { E1, E2, … }; , so the following auto a = make_array(42u, 3.14); is well-formed … Read more
Your first example is not standard C++ but is an extension that both gcc and clang allow, it is version of flexible arrays and this answer to the question: Are flexible array members really necessary? explains the many advantages of this feature. If you compiled using the -pedantic flag you would have received the following … Read more
std::array is, by design, an aggregate, so has no user-declared constructors. As you say, you could use fill after default constructing. Since it’s an aggregate, default construction won’t zero the memory, but will leave it uninitialised (if the contained type is trivially initialisable).
Is there a simple way to make this work, as one would with plain C-style arrays? No. You really cannot do that unless you make your function a function template (or use another sort of container, like an std::vector, as suggested in the comments to the question): template<std::size_t SIZE> void mulArray(std::array<int, SIZE>& arr, const int … Read more
By definition, default initialization is the initialization that occurs when no other initialization is specified; the C++ language guarantees you that any object for which you do not provide an explicit initializer will be default initialized (C++11 ยง8.5/11). That includes objects of type std::array<T, N> and T[N]. Be aware that there are types for which … Read more
What are the advantages of using std::array over usual ones? It has friendly value semantics, so that it can be passed to or returned from functions by value. Its interface makes it more convenient to find the size, and use with STL-style iterator-based algorithms. Is it more performant ? It should be exactly the same. … Read more