Segmentation fault pushing three floats to a Stack

[André Matheus]

Hello,

I'm learning ocaml and was trying to implement an exercise from programming praxis using Core.

As I've used it, I've started to get segmentation faults. After some debugging it became clear the

problem is pushing more than three floats to a Stack. I can reproduce it on utop:

open Core.Std;;

let s = Stack.create();;

Stack.push s 1.0;;

Stack.push s 2.0;;

Stack.push s 3.0;;   <<-- at this point I get "Segmentation fault: 11"

Am I doing something wrong? Ocaml's Stack works fine, it's just Core's that give this problem.

I'm testing this on a Mac, running el captain 10.11.3. Ocaml 4.02.2. Core:

core                 113.24.02  Industrial strength alternative to OCaml's stand

core_kernel          113.24.00  Industrial strength alternative to OCaml's stand

ppx_core             113.24.00  Standard library for ppx rewriters

Creating a stack of ints works fine.

Thanks,

André

[Arseniy Alekseyev]

This is a hilariously simple bug description and I can actually reproduce this (so it's not a subtle mac-specific thing)... 

I love how you quoted "industrial strength" next to this bug report. :)

I'll investigate and it will probably be fixed.

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[Yaron Minsky]

Ouch. That's deeply embarrassing.

y

[Stanislav Artemkin]

It seems the problem is in treating the array (tag 0) as a floating array (tag 254).

It literally does this:

let elts = [|Obj.magic();Obj.magic()|];;

elts.(0) <- 1.0;;

elts.(1) <- 2.0;;

elts;;

Segmentation fault: 11

[Yaron Minsky]

This is a poor excuse for a fix (we're working on that too), but you
can use Linked_stack, which has the same API but a different
implementation that is not exposed to this bug. (It also has
different performance characteristics.)

y

[André Matheus]

Hi all,

Thanks for all the prompt replies.

I've replaced Stack with Linked_stack and it worked, thanks Yaron.

Arseniy, when I've wrote the email I didn't meant to quote "industrial strength"

as irony or anything, I was just lazy to type the versions and copy pasted them

from the terminal, sorry if it sounded snarky.

If there's anything else I can do to help with solving it please let me know.