Stack overflow while updating repositories

[kit-ty-kate]

Using 2.4.0~alpha2:

$ opam init --reinit -ni --debug-level=3
[...]
01:48.863  REPO_BACKEND           diff: /home/kit_ty_kate/.opam/repo/{default,default.new}
03:59.309  REPO_BACKEND           Internal diff (non-empty) done in 130.45s.
03:59.767  SYSTEM                 rmdir /home/kit_ty_kate/.opam/repo/default.new
05:32.007  SYSTEM                 rmdir /home/kit_ty_kate/.opam/repo/default.new
[ERROR] Could not update repository "default": Stack overflow
05:32.010  PARALLEL               Job 0 finished

This happened on an OpenBSD machine whose ulimits look like this:

$ ulimit -a
time(cpu-seconds)    unlimited
file(blocks)         unlimited
coredump(blocks)     unlimited
data(kbytes)         1572864
stack(kbytes)        4096
lockedmem(kbytes)    87381
memory(kbytes)       976504
nofiles(descriptors) 512
processes            256

[kit-ty-kate]

Reproducing using ocaml/opam-repository#2025-01-before-archiving-phase1 as a base and updating to the latest opam-repository, it locally brought up hannesm/patch#28.

Once fixed, i was able to reproduce it on a Linux machine, but only when opam is compiled using OCaml < 5. With OCaml 5 it works fine. I believe this is due to ocaml/ocaml#11859.

I'll review the non-tail-call functions in patch tomorrow but it should be a fairly easy fix on our end: just update to the next version of patch.

[hannesm]

I marked all let rec calls with (call [@tailcall]) in patch, but wasn't able to get any compiler warnings. Are you able to get a stacktrace from the issue?

[kit-ty-kate]

As far as i know [@tailcall] doesn't work for functions outside the current scope (i.e. Stdlib.(@), see the link to the ocaml PR). What's happening is that it stacks overflow when we're diffing large files because hunk.mine or hunk.their is larger than the max stack size.

Dw, i'm on it, i'll send a patch by tonight