# IntSet crashes Julia 0.6.1

**URL:** <https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727>\
**Category:** General Usage\
**Created:** [October 27, 2017, 6:03pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727 "2017-10-27T18:03:01Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![Andrea\_Pagnani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/andrea_pagnani/32/3136_2.png) [@Andrea\_Pagnani](https://discourse.julialang.org/u/Andrea_Pagnani)\
**Post date:** [October 27, 2017, 6:03pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/1 "2017-10-27T18:03:01Z")

</div>

Dearests,

The following

```julia
julia> N=2^10; a= rand(UInt64,N); sa=IntSet(a); #gives an error ... which is fine
ERROR: InexactError()
....
julia> a= rand(UInt32,N); sa=IntSet(a); #now the system crashes
signal (11): Segmentation fault: 11
...

```

Note that the segfault occurs (systematically) only after the the first error is produced. Indeed, the help on IntSet constructor says

```julia
  [...] Only Ints greater than 0 can be stored. If the set
  will be sparse (for example holding a few very large integers), use Set
  instead.

```

and perhaps it is not a bug. However, let me know it you think it’s worth reporting _upstream_…

I’m on

```julia
Version 0.6.1 (2017-10-24 22:15 UTC)
x86_64-apple-darwin15.6.0

```

Cheers

Andrea

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<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [October 27, 2017, 6:26pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/2 "2017-10-27T18:26:46Z")

</div>

I get various errors, but never manage to crash Julia (`v0.6.1`, on Linux). These are typical:

```julia
julia> N=2^10; a= rand(UInt64,N); sa=IntSet(a);
ERROR: OutOfMemoryError()
Stacktrace:
 [1] resize!(::BitArray{1}, ::UInt64) at ./bitarray.jl:836
 [2] _resize0!(::BitArray{1}, ::UInt64) at ./intset.jl:35
 [3] _setint! at ./intset.jl:25 [inlined]
 [4] push! at ./intset.jl:69 [inlined]
 [5] union!(::IntSet, ::Array{UInt64,1}) at ./intset.jl:95
 [6] IntSet(::Array{UInt64,1}) at ./intset.jl:7

julia> N=2^10; a= rand(UInt64,N); sa=IntSet(a);
ERROR: InexactError()
Stacktrace:
 [1] resize!(::BitArray{1}, ::UInt64) at ./bitarray.jl:834
 [2] _resize0!(::BitArray{1}, ::UInt64) at ./intset.jl:35
 [3] _setint! at ./intset.jl:25 [inlined]
 [4] push! at ./intset.jl:69 [inlined]
 [5] union!(::IntSet, ::Array{UInt64,1}) at ./intset.jl:95
 [6] IntSet(::Array{UInt64,1}) at ./intset.jl:7

julia> N=2^10; a= rand(UInt64,N); sa=IntSet(a);
ERROR: ArgumentError: elements of IntSet must be between 1 and typemax(Int)
Stacktrace:
 [1] _throw_intset_bounds_err() at ./intset.jl:64
 [2] push! at ./intset.jl:68 [inlined]
 [3] union!(::IntSet, ::Array{UInt64,1}) at ./intset.jl:95
 [4] IntSet(::Array{UInt64,1}) at ./intset.jl:7

```

Perhaps to make the error reproducible you could include a random seed.

---

<div class="post-metadata">

**Author:** ![ExpandingMan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/expandingman/32/866_2.png) [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Post date:** [October 27, 2017, 6:41pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/3 "2017-10-27T18:41:30Z")

</div>

Same as @Tamas_Papp, I get the correct errors (oxy moron?), but Julia doesn’t crash. This on x86\_64 Linux.

In the past I’ve noticed that segfaults can pop up at very unexpected times in Julia; is it possible you ran some other code prior to this that was the real cause?

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<div class="post-metadata">

**Author:** ![Andrea\_Pagnani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/andrea_pagnani/32/3136_2.png) [@Andrea\_Pagnani](https://discourse.julialang.org/u/Andrea_Pagnani)\
**Post date:** [October 27, 2017, 6:50pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/4 "2017-10-27T18:50:22Z")

</div>

The second time shoul be run with UInt32 as in my example … an yes it is in a fresh session.

---

<div class="post-metadata">

**Author:** ![mbauman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mbauman/32/31082_2.png) [@mbauman](https://discourse.julialang.org/u/mbauman)\
**Post date:** [October 27, 2017, 6:52pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/5 "2017-10-27T18:52:52Z")

</div>

Yes, there’s likely something fishy going on here with `UInt32` arithmetic in the internals of the IntSet.

```julia
julia> IntSet(UInt32(2^32-1))
IntSet([])

julia> IntSet((2^32-1))
IntSet([4294967295])

```

Edit: caught it:

```julia
julia> Base._setint!(IntSet(), UInt32(2^32-10), true)

signal (11): Segmentation fault: 11
while loading no file, in expression starting on line 0
unsafe_bitsetindex! at ./bitarray.jl:675 [inlined]
setindex! at ./bitarray.jl:682 [inlined]
_setindex! at ./abstractarray.jl:979 [inlined]
setindex! at ./abstractarray.jl:967 [inlined]
_setint! at ./intset.jl:27

```

Note that those stack traces are actually _very_ helpful!

And with `--check-bounds=yes`:

```julia
julia> Base.push!(IntSet(), UInt32(2^32-10), true)
ERROR: BoundsError: attempt to access 2147483633-element BitArray{1} at index [4294967286]
Stacktrace:
 [1] throw_boundserror(::BitArray{1}, ::Tuple{Int64}) at ./abstractarray.jl:433
 [2] checkbounds at ./abstractarray.jl:362 [inlined]
 [3] setindex! at ./bitarray.jl:681 [inlined]
 [4] _setindex! at ./abstractarray.jl:979 [inlined]
 [5] setindex! at ./abstractarray.jl:967 [inlined]
 [6] _setint! at ./intset.jl:27 [inlined]
 [7] push!(::IntSet, ::UInt32) at ./intset.jl:69
 [8] push!(::IntSet, ::UInt32, ::Bool) at ./intset.jl:71

```

---

<div class="post-metadata">

**Author:** ![ExpandingMan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/expandingman/32/866_2.png) [@ExpandingMan](https://discourse.julialang.org/u/ExpandingMan)\
**Post date:** [October 27, 2017, 7:15pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/6 "2017-10-27T19:15:32Z")

</div>

I’m confused

```julia
julia> IntSet(UInt32(2^32-1))
ERROR: ReadOnlyMemoryError()
Stacktrace:
 [1] unsafe_bitsetindex! at ./bitarray.jl:675 [inlined]
 [2] setindex! at ./bitarray.jl:682 [inlined]
 [3] _setindex! at ./abstractarray.jl:980 [inlined]
 [4] setindex! at ./abstractarray.jl:968 [inlined]
 [5] _setint! at ./intset.jl:27 [inlined]
 [6] push! at ./intset.jl:69 [inlined]
 [7] union!(::IntSet, ::UInt32) at ./intset.jl:95
 [8] IntSet(::UInt32) at ./intset.jl:7

julia> IntSet((2^32-1))
IntSet([4294967295])

julia> Base._setint!(IntSet(), UInt32(2^32-10), true)
IntSet([])

```

---

<div class="post-metadata">

**Author:** ![mbauman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mbauman/32/31082_2.png) [@mbauman](https://discourse.julialang.org/u/mbauman)\
**Post date:** [October 27, 2017, 7:19pm UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/7 "2017-10-27T19:19:18Z")

</div>

IntSet isn’t allocating enough space for the large `UInt32` because it’s overflowing when it tries to compute how much space is required. So then it ends up writing out of bounds inside an `@inbounds` block. The behavior you see will vary depending upon where that out-of-bounds write lands: It could be in a read-only memory area, or it could silently corrupt something else, or it could crash.

[https://github.com/JuliaLang/julia/pull/24365](https://github.com/JuliaLang/julia/pull/24365)

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<div class="post-metadata">

**Author:** ![Andrea\_Pagnani](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/andrea_pagnani/32/3136_2.png) [@Andrea\_Pagnani](https://discourse.julialang.org/u/Andrea_Pagnani)\
**Post date:** [October 28, 2017, 7:22am UTC](https://discourse.julialang.org/t/intset-crashes-julia-0-6-1/6727/8 "2017-10-28T07:22:17Z")

</div>

Wow … quite a lot of activity on this! @mbauman, thanks a lot for detecting and solving the problem

A