1.9.2 Base.map!(|,a,a,b) yields wrong answer on BitVector

[StephenVavasis]

The testset for the DataStructures.jl package are now failing in 1.9.2. In particular, IntSet is not working. I have traced the error to a bug with the Base.map! function applied to BitVector. See below for the incorrect output from map!:

EDIT: I did not report this bug correctly in my first post. The bug is actually with map!(|,a,a,b) not with map!(|,a,b). Please refer to my follow-up post below.

julia> a = BitVector([1,1,0,0,1,1,0,0]);

julia> b = BitVector([1,0,1,0,1,0,1,0]);

julia> map!(|, a, b);

julia> a
8-element BitVector:
 1
 0
 1
 0
 1
 0
 1
 0

[adienes]

that looks correct to me, what output were you expecting?

note that map! here is doing something equivalent to a .= .|(b), not a .= .|(a, b)

[StephenVavasis]

You are right, sorry. I will close this issue. But I am now confused how union of two IntSets is supposed to work since it seems to rely on map!(|,a,b) replacing a with the bitwise OR of a and b in line 94 of int_set.jl in the DataStructures package. And apparently this statement worked fine in pre-1.9 versions of Julia.

[oscardssmith]

well that doesn't work in 1.8.5 at least...

   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.8.5 (2023-01-08)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> map!(|, [false, true], [true, false])
2-element Vector{Bool}:
 1
 0

julia> map!(|, BitVector([false, true]), BitVector([true, false]))
2-element BitVector:
 1
 0

[StephenVavasis]

Wait! There is a new bug in Base.map! I am reopening this issue. Here is the bug. It is with map!(a,a,b), not map!(a,b) as I said earlier. Sorry for the confusion. I have confirmed that this behavior has changed since 1.6.7.

julia> a = BitVector([1,1,0,0,1,1,0,0]);

julia> b = BitVector([1,0,1,0,1,0,1,0]);

julia> map!(|,a,a,b);

julia> a
8-element BitVector:
 1
 0
 1
 0
 1
 0
 1
 0

[oscardssmith]

Specifically the problem is new in 1.9 and affects the last chunk of the array and is caused by #47013.

[oscardssmith]

For another related bug:

julia> a = BitVector([1,0])
2-element BitVector:
 1
 0

julia> map!(!, a, a)
2-element BitVector:
 1
 1

[oscardssmith]

luckily it's easy to fix. Thanks for the report!