no bound checks anymore on some array operations

[vicuna]

Original bug ID: 5742
Reporter: @lefessan
Status: closed (set by @xavierleroy on 2015-12-11T18:19:36Z)
Resolution: fixed
Priority: high
Severity: crash
Version: 4.00.0
Fixed in version: 4.00.1+dev
Category: standard library
Monitored by: @gasche @hcarty @dbuenzli @alainfrisch

Bug description

$ ocaml
OCaml version 4.00.0

Array.sub [||] 0 10;;

• : '_a array =
  [|; ; ; ; ; ; ; ; ;
  |]

probably since commit 11913:

Module Array: faster implementations of "blit", "copy", "sub",
"append" and "concat" (#2395, #2787, #4591)

[vicuna]

Comment author: @xavierleroy

Indeed, the bound check in Array.sub fell through the cracks during commit 11913. Reinstated proper bound checks + a test in the testsuite, commits
r12891 (4.00 bugfix branch) and r12892 (trunk).