What is wrong with this code?

Mojo
1

Can anyone help me fix this code:

var ptr = alloc[List[Int]](10)
for i in range(10):
    ptr.store(i, [1234])
ptr.free()

Error:

error: no matching method in call to 'store'
        ptr.store(i, [1234])
        ~~~^~~~~~
2

I am getting the same error when using Mojo 0.26.2.0.dev2026021605 (eb42a2ba).

When I run this I can see the pointer already has empty lists:

fn main() raises -> None:
    var ptr = alloc[List[Int]](8)
    for i in range(8):
        print(i, ptr[i])

So this does work:

fn main() raises -> None:
    var ptr = alloc[List[Int]](8)
    for i in range(8):
        ptr[i].append(1234)
        print(i, ptr[i])
3

I run this code and got core dumped. Can you help?

var s = ""
for _ in range(1000):
    s += "0123456789"

var ptr = alloc[List[Int]](8)
for i in range(8):
    ptr[i].append(1234)
    print(i, ptr[i])
ptr.free()
4

On my side if I set the capacity to 25 or more I no longer get a core dumped.

fn main() raises -> None:
    var s = String(capacity=25)
    for _ in range(1000):
        s += "0123456789"
    print(len(s))

    var ptr = alloc[List[Int]](8)
    for i in range(8):
        ptr[i].append(1234)
        print(i, ptr[i])
    ptr.free()

Not sure why that is though.

5

List manages allocation itself, so you’re accessing off the end of an array of List[Int] values.