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Bug is List.sort #2520

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vicuna opened this issue Jul 6, 2000 · 1 comment
Closed

Bug is List.sort #2520

vicuna opened this issue Jul 6, 2000 · 1 comment
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@vicuna
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vicuna commented Jul 6, 2000 •
edited by nojb

Original bug ID: 156
Reporter: administrator
Status: closed
Resolution: fixed
Priority: normal
Severity: minor
Category: ~DO NOT USE (was: OCaml general)

Bug description

Hello,
The following program crashes:

let _ = 
  let a = Array.init 100 (fun _ -> Random.float 1.0) in
  let l = Array.to_list a in
  let l = List.sort compare l in
  ()

Fatal error: uncaught exception Invalid_argument("Array.get")

It must be a bug in List.sort, because with Array.sort this works fine.
I may add a request, as has been discussed in the list recently, to add
an optional feature that shows where the exception was thrown. This
(new) bug has occured in a 100,000 lines of code system (Ensemble). It is
difficult to find a bug in such a large system without language level
help.

Thanks,
Ohad.
@vicuna
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vicuna commented Jul 8, 2000 •
edited by nojb

Comment author: administrator

From: orodeh@cs.huji.ac.il

let _ =
let a = Array.init 100 (fun _ -> Random.float 1.0) in
let l = Array.to_list a in
let l = List.sort compare l in
()

Fatal error: uncaught exception Invalid_argument("Array.get")

It must be a bug in List.sort, because with Array.sort this works fine.

This is a bug in Obj.truncate, which makes List.sort fail on all lists
of floats (except the empty list), but only on 32-bit machines. Many
thanks for finding and reporting the bug. I'm including a patch at the
end of this mail.

-- Damien

Index: byterun/obj.c
===================================================================
RCS file: /net/pauillac/caml/repository/csl/byterun/obj.c,v
retrieving revision 1.13
diff -c -r1.13 obj.c
*** obj.c       2000/04/03 08:34:22     1.13
--- obj.c       2000/07/08 18:33:33
***************
*** 102,107 ****
--- 102,109 ----
    mlsize_t wosize = Wosize_hd (hd);
    mlsize_t i;
  
+   if (tag == Double_array_tag) new_wosize *= Double_wosize;  /* #2520 */
+ 
    if (new_wosize <= 0 || new_wosize > wosize) 
      invalid_argument ("Obj.truncate");
    if (new_wosize == wosize) return Val_unit;

@vicuna vicuna closed this as completed Jul 8, 2000
@vicuna vicuna added the bug label Mar 19, 2019
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@vicuna