On Saturday, June 06, 2015 09:44:36 Tim K. via Digitalmars-d-learn wrote:
> Hello!
>
> I just started learning D and I come from a mostly C and C#
> background.
> Hello World was working, so I figured that I should try something
> more complex: a template class and si I went with a simple stack.
>
> Using dmd the code I wrote causes a segmentation fault and I am
> not sure why.
>
> import std.stdio;
> import std.container.slist;
>
>
> class Stack(T)
> {
> SList!(T) s;
> this() {}
> void push(T element)
> {
> s.insertFront(element);
> }
> }
>
> int main()
> {
> Stack!(int) x;
> writeln("1");
> SList!(int) p;
> writeln("2");
> p.insertFront(42);
> writeln("3");
> x.push(42);
> writeln("4");
> return 0;
> }
>
>
> This program prints the following into the console:
> % dmd test.d && ./test
> 1
> 2
> 3
> zsh: segmentation fault ./test
>
>
> I do not understand why the normal SList works fine but the one
> inside the object doesn't. What am I overlooking?
>From the looks of it, you never initialized x, so it's null. So, the problem
has nothing to do with SList. It's the fact that you're trying to
dereference a null reference. You need to call new to allocate a Stack!int,
not just declare a reference to one.
void main()
{
Stack!int x
x.push(42);
}
would have exactly the same problem. You need something like
auto x = new Stack!int;
- Jonathan M Davis
