Segfault when testing under v0.4.6 on Ubuntu 16.04

[dmbates]

I am consistently getting segfaults under v0.4.6 when testing the release version or the master branch. On the master branch of CategoricalArrays I get a series of warnings about overwriting convert methods

julia> Pkg.test("CategoricalArrays")
INFO: Computing test dependencies for CategoricalArrays...
INFO: No packages to install, update or remove
INFO: Testing CategoricalArrays
INFO: Recompiling stale cache file /home/bates/.julia/lib/v0.4/CategoricalArrays.ji for module CategoricalArrays.
WARNING: Method definition convert(Type{Array{#T<:Any, N<:Any}}, AbstractArray{#S<:Any, #n<:Any}) in module Base at array.jl:240 overwritten in module CategoricalArrays at /home/bates/.julia/v0.4/CategoricalArrays/src/CategoricalArrays.jl:18.
WARNING: Method definition convert(Type{Array{#T<:Any, #n<:Any}}, AbstractArray{#S<:Any, #n<:Any}) in module Base at array.jl:241 overwritten in module CategoricalArrays at /home/bates/.julia/v0.4/CategoricalArrays/src/CategoricalArrays.jl:19.
WARNING: Method definition convert(Type{Base.Nullable}, #T<:Any) in module Base at nullable.jl:19 overwritten in module CategoricalArrays at /home/bates/.julia/v0.4/CategoricalArrays/src/CategoricalArrays.jl:21.
WARNING: New definition 
    convert(Type{CategoricalArrays.NominalPool{#S<:Any, #R<:Any, V<:Any}}, CategoricalArrays.NominalPool) at /home/bates/.julia/v0.4/CategoricalArrays/src/pool.jl:54
is ambiguous with: 
    convert(Type{CategoricalArrays.NominalPool{#T<:Any, #R<:Any, V<:Any}}, CategoricalArrays.NominalPool{#T<:Any, #R<:Any, V<:Any}) at /home/bates/.julia/v0.4/CategoricalArrays/src/pool.jl:51.
To fix, define 
    convert(Type{CategoricalArrays.NominalPool{#S<:Any, #R<:Any, V<:Any}}, CategoricalArrays.NominalPool{#S<:Any, _<:Integer, V<:Any})
before the new definition.

culminating in

ARNING: New definition 
    convert(Type{CategoricalArrays.NullableOrdinalArray{#T<:Any, #N<:Any, #R<:Any}}, CategoricalArrays.NullableOrdinalArray) at /home/bates/.julia/v0.4/CategoricalArrays/src/array.jl:92
is ambiguous with: 
    convert(Type{CategoricalArrays.NullableOrdinalArray{#T<:Any, #N<:Any, #R<:Any}}, CategoricalArrays.NullableOrdinalArray{#T<:Any, #N<:Any, #R<:Any}) at /home/bates/.julia/v0.4/CategoricalArrays/src/array.jl:59.
To fix, define 
    convert(Type{CategoricalArrays.NullableOrdinalArray{#T<:Any, #N<:Any, #R<:Any}}, CategoricalArrays.NullableOrdinalArray{#T<:Any, #N<:Any, _<:Integer})
before the new definition.

signal (11): Segmentation fault
unknown function (ip: 0x7ff5d2f3cf76)
unknown function (ip: 0x7ff5d2f3d0d5)
unknown function (ip: 0x7ff5d2f3ddeb)
unknown function (ip: 0x7ff5d2f3d0d5)
unknown function (ip: 0x7ff5d2f3ddeb)
unknown function (ip: 0x7ff5d2f3d0d5)
unknown function (ip: 0x7ff5d2f3ddeb)
unknown function (ip: 0x7ff5d2f3d0d5)
unknown function (ip: 0x7ff5d2f3d0d5)
unknown function (ip: 0x7ff5d2f3d0d5)

Although CategoricalArrays is the package that triggers this segfault, it looks like it is a problem in Julia itself.

[nalimilan]

That's most likely one of the crashes we experienced with @quinnj. Cf. JuliaLang/julia#18343. Shouldn't happen anymore with the latest version thanks to a workaround, but please report if you see it again.

[quinnj]

FYI, I'm still seeing a crash on 0.4.7: https://travis-ci.org/JuliaData/DataStreams.jl/jobs/161515557

[nalimilan]

We no longer support 0.4.