empty!(::WeakKeyDict) throws error

[dbeach24]

Demonstration:

julia> versioninfo()
Julia Version 0.6.0-dev.374
Commit 7199111* (2016-08-23 15:07 UTC)
Platform Info:
  System: Darwin (x86_64-apple-darwin14.5.0)
  CPU: Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.7.1 (ORCJIT, haswell)

julia> x = WeakKeyDict{Int,Int}()
WeakKeyDict{Int64,Int64} with 0 entries

julia> empty!(x)
ERROR: MethodError: no method matching lock(::Base.##378#379{WeakKeyDict{Int64,Int64}})
Closest candidates are:
  lock(::Any, ::WeakKeyDict{K,V}) at weakkeydict.jl:21
  lock(::Any, ::Any) at lock.jl:99
  lock(::Base.Threads.Mutex) at locks.jl:206
  ...
 in empty!(::WeakKeyDict{Int64,Int64}) at ./weakkeydict.jl:48

I found this while reading the source (line 49 of base/weakkeydict.jl):

empty!(wkh::WeakKeyDict) = (lock(() -> empty!(wkh.ht)); wkh)

Probably was meant to be:

empty!(wkh::WeakKeyDict) = lock(() -> empty!(wkh.ht), wkh)

[mauro3]

On 0.6 this seems to work now. On 0.5, this actually segfaults when there is an non-empty dict:

julia> x = WeakKeyDict()
WeakKeyDict{Any,Any} with 0 entries

julia> x[BigFloat(1)] = 1
1

julia> empty!(x)

signal (11): Segmentation fault
while loading no file, in expression starting on line 0
unknown function (ip: 0x7fbe65b5dd0e)
decompose at ./hashing2.jl:140
hash at ./hashing2.jl:32
hashindex at ./dict.jl:441 [inlined]
ht_keyindex at ./dict.jl:536
delete! at ./dict.jl:736 [inlined]
#374 at ./weakkeydict.jl:49
lock at ./lock.jl:101
#356 at ./weakkeydict.jl:15
jl_call_method_internal at /home/mauro/julia/julia-0.5/src/julia_internal.h:189 [inlined]
...

Worth a back-port? (Not for me, I don't use it)

[kshyatt]

I think I fixed this in #19485 ? Should I open a PR against release-0.5 to fix the bug there, @tkelman ?

[tkelman]

It's just a matter of backporting that PR but without using a testset, right?

[kshyatt]

I think so.

[tkelman]

Unless you plan on running pkgeval on backports, I'll get it.

[kshyatt]

Thanks!