IPython shell segfault on tab completion

[simonbyrne]

In the ipython shell:

import julia
j = julia.Julia()
j.<tab>

immediately segfaults.

On OS X:

Python 3.6.3 (default, Oct  4 2017, 06:09:05) 
Type 'copyright', 'credits' or 'license' for more information
IPython 6.0.0 -- An enhanced Interactive Python. Type '?' for help.

[simonbyrne]

Interestingly, it's fine in the normal python3 shell. So maybe it's an IPython issue?

[stevengj]

IPython does tab completion differently than python3, but it's probably ultimately a pyjulia bug that is being triggered.

[zsunberg]

On linux with ipython 5.1.0, I am able to do tab completion of methods of the Julia object, but when I try to complete filenames in a string, it segfaults, e.g.

In [1]: import julia

In [2]: j = julia.Julia()

In [3]: j.evalfile("new<tab>
signal (11): Segmentation fault                                               
while loading no file, in expression starting on line 0                       
Segmentation fault

[tkf]

As @takluyver guessed in ipython/ipython#10899 (comment), it looks like threading problem. Just in case if someone wants to reproduce the problem in a script, here it is:

import threading

from IPython.testing.globalipapp import get_ipython
from julia import Julia

ip = get_ipython()
ip.user_ns['julia'] = Julia()


def ip_complete():
    print(ip.complete('julia.sin.'))


print("ip_complete() in main thread:")
ip_complete()
print()

print("ip_complete() in different thread:")
th = threading.Thread(target=ip_complete)
th.start()
th.join()

It prints

ip_complete() in main thread:
('julia.sin.', ['julia.sin.jl_value'])

ip_complete() in different thread:

signal (11): Segmentation fault

I wonder if PyCall/libjulia can support multi-thread usage. JuliaLang/julia#17573

[tkf]

Of course, producing segfault this way doesn't require IPython:

import threading

from julia import Julia

j = Julia()
j_sin = j.sin


def access_julia():
    j_sin.jl_value


th = threading.Thread(target=access_julia)
th.start()
th.join()

[takluyver]

When prompt_toolkit version 2 is ready, we (IPython) should be able to do completions in the main thread, which should avoid this kind of issue. A few things have come up that don't like their completions running from another thread.

[tkf]

@takluyver Thanks. That would be awesome.

[tkf]

I just found out that IPython master (to be released as 7.0) already was upgraded to use prompt_toolkit 2.0! ipython/ipython#11177 I have to try it soon...

FYI, here is IPython's 7.0 milestone https://github.com/ipython/ipython/milestone/43

[tkf]

Yes, tab completion in IPython master works with pyjulia!

[tkf]

IPython 7.0 is already released and available in PyPI and Anaconda. Closing...