C++ : Declaring the array size with a non-constant variable
- by Jérôme
I always thought that when declaring an array in C++, the size has to be a constant integer value.
For instance :
int MyArray[5]; // correct
or
const int ARRAY_SIZE = 6;
int MyArray[ARRAY_SIZE]; // correct
but
int ArraySize = 5;
int MyArray[ArraySize]; // incorrect
Here is also what is explained in The C++ Programming Language, by Bjarne Stroustrup :
The number of elements of the array, the array bound, must be a constant expression (§C.5).
If you need variable bounds, use a vector(§3.7.1, §16.3). For example:
void f(int i) {
int v1[i]; // error : array size not a constant expression
vector<int> v2[i]; // ok
}
But to my big surprise, the code above does compile fine on my system !
Here is what I tried to compile :
void f(int i) {
int v2[i];
}
int main()
{
int i = 3;
int v1[i];
f(5);
}
I got no error !
I'm using GCC v4.4.0.
Is there something I'm missing ?
