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Array.init evaluates callback although it should not do so #6575

vicuna opened this issue Sep 23, 2014 · 1 comment


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commented Sep 23, 2014

Original bug ID: 6575
Reporter: gerd
Assigned to: @alainfrisch
Status: closed (set by @xavierleroy on 2017-02-16T14:18:27Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 4.02.0
Target version: 4.02.2+dev / +rc1
Category: standard library
Related to: #4950
Monitored by: @hcarty

Bug description

Look at this (ocaml-4.02):

let n = 0 ;;
ignore (Array.init (n-1) (fun _ -> assert false));;

$ ocamlopt -o m
$ ./m
Fatal error: exception Assert_failure("", 2, 35)

Same with ocamlc.

Additional information

This is straight-forward from the definition of Array.init, but nevertheless quite surprising behavior, because all other stdlib functions check the arguments before calling anything back.


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commented Mar 11, 2015

Comment author: @alainfrisch

Commit 15898 on 4.02, 15899 on trunk. I've added a check for size < 0 before calling Array.make. Notes:

  • Array.init used to raise (Invalid_argument "Array.make") in that case, not it raises (Invalid_argument "Array.init"). I don't expect this to break any code and is clearly better.

  • Checking for the maximum array size is more difficult, since this size depends on whether we are building an array of floats or a regular array (and we don't know before calling the initializer once). Anyway, it is less clear that when the size is too large, the callback should not be called at all.

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