C++20 introduced support for designated initializers. In g++ with -std=c++17, one can use designated initializers and as long as you don’t leave any out, it will compile without any errors or warnings: struct Foo { int a; float b; }; Foo f { .a = 7, .b = 42.1f, }; Yet if I enable -Wpedantic ..
Category : aggregate-initialization
In the following program the union U has two fields a and b, each with distinct default value. If one creates a variable of type U using aggregate initialization {} what are the value and the active member of the union? #include <iostream> struct A { int x = 1; }; struct B { int ..
Please consider the code with aggregate struct B having a field of class A with a private constructor: class A { A(int){} friend struct B; }; struct B { A a{1}; }; int main() { B b; //ok everywhere, not aggregate initialization //[[maybe_unused]] B x{1}; //error everywhere [[maybe_unused]] B y{}; //ok in GCC and Clang, ..
I have a struct struct RGB { int r; int g; int b; } I know that aggregate initialization can be used: RGB rgb = {255, 255, 255}; I wonder if it is possible to initialize it using an array. I’ve tried these solutions and they do not work: int rgb_array[] = {255, 255, 255}; ..
I have a struct struct RGB { int r; int g; int b; } I know that aggregate initialization can be used: RGB rgb = {255, 255, 255}; I wonder if it is possible to assign an array to it. I’ve tried these solutions and they do not work: int rgb_array[] = {255, 255, 255}; ..
TL;DR : I need global objects to be initialized at compile time, and I cannot use constexpr constructors. Can I use aggregate initializers for this task? I know that C/C++ aggregate initializers can be used to initialize an object’s public members like this : MyObj obj = { "object1", 3, 7.2F }; I discovered their ..
Aggregate initialization is a special form of list initialization which can be used for aggregate types. An aggregate is an array or a class ([class]) with (1.1) no user-declared or inherited constructors ([class.ctor]), (1.2) no private or protected direct non-static data members ([class.access]), (1.3) no virtual functions ([class.virtual]), and (1.4) no virtual, private, or protected ..
Please consider this short code example: #include <iostream> struct A { A() { std::cout << "A() "; } ~A() { std::cout << "~A() "; } }; struct B { const A &a; }; struct C { const A &a = {}; }; int main() { B b({}); std::cout << ". "; C c({}); std::cout << ..
As far as I understand, the following program should work in C++20 mode: #include <vector> struct B{ int a0, a1; }; int main() { std::vector<B> bs; bs.emplace_back( 0, 0 ); } And it really does in Visual Studio 2019 and gcc 11. But not in clang 12, which produces the error: /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/12.0.0/../../../../include/c++/12.0.0/bits/alloc_traits.h:514:4: error: no matching ..
I have this piece of code in C++: std::array<std::array<int, 2>, 4> elements = {{1,2},{1,2},{1,2},{1,2}}; and it says: error: excess elements in struct initializer I don’t know why that happens. If I write that it works: std::array<std::array<int, 2>, 4> elements = {{1,2}}; Source: Windows Que..
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