When I declare a structure instance is it initialized or do I have to make a constructor?
How much will the constructor affect the performance since I need an array of 1000 structures?
The structure I need is very simple and it contains 4 integers. I need them to be initialized to 0.
This is my code:
struct MyStruct { int a; int b; int c; int d; MyStruct() : a(0), b(0), c(0), d(0) {} }; int main() { MyStruct array[1000]; } You are declaring a variable in main, but only as a side-effect of defining it.
And all objects are default-initialized, unless you ask for something else.
Still, that's not quite as much as you might thing. A default-initialized basic type, which is neither in static nor in thread-local storage, is still indeterminate after that.
But never fear, your type has a user-defined default-ctor, so default-initialization means that is called.
And as that value-initializes all members, everything is initialized.
If it was an aggregate, this would zero-initialize it:
MyStruct array[1000] = {}; Regarding performance, there's nothing to be done but measuring, and asking the compiler to optimize it. Keep in mind that the fastest code is code that isn't there.
MyStruct array[1000]{}; to conserve the limited supply of characters.
MyStruct array[1000]()which will zero-initialize all the integers.declaration of 'array' as array of functionsAre you sure that's correct syntax?MyStruct array[1000]{}(which only works >=C++11)