StackOverflowError on key-press-event callback

[jpsamaroo]

Hey all, I'm trying to get keyboard keys to work for a project I'm doing which uses Gtk as the frontend. I'm currently getting a StackOverflowError everytime I press a key. I'm running Julia 0.6 RC 1, Gtk.jl master, and with GTK+ 3.22.12 on Xorg installed on my Gentoo Linux system. Here's a MWE:

using Gtk, Gtk.ShortNames

win = Window("Test")
signal_connect(win, "key-press-event") do widget, event
  @async println("Key: ", event.keyval)
end
signal_connect(win, "destroy") do widget
  exit(0)
end
showall(win)

while true
  sleep(1)
end

And here's the error:

WARNING: Executing #1:
ERROR: StackOverflowError:
Stacktrace:
 [1] convert(::Type{Gtk.GdkEvent}, ::Ptr{Gtk.GdkEvent}) at /home/jpsamaroo/.julia/v0.6/Gtk/src/GLib/gtype.jl:283 (repeats 80000 times)

My versioninfo():

Julia Version 0.6.0-rc1.0
Commit 6bdb395* (2017-05-07 00:00 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i5-3230M CPU @ 2.60GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Sandybridge)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, ivybridge)

I wouldn't be surprised if I'm just doing something terribly stupid, so please let me know if that's the case 😄

[lobingera]

I can reproduce and my first order assumption is a missing v0.6 update to Gtk and some interaction with async.

I reduced to display(event) only and get the same error StackOverflowError which is somehow understandable looking at the convert method.
Then i ran on 0.5 with key value output (with async println) and some warning about Task (async?) and correctly with display.

And then i thought 'hey, other packages might do similar with Gtk', did a Pkg.update and landed in dependency hell. Maybe more later.

[timholy]

I wonder if this is actually a Julia bug. Check this out:

julia> using Gtk

julia> methods(convert, (Gtk.GdkEvent, Ptr{Gtk.GdkEvent}),)
# 0 methods for generic function "convert":

julia> methods(convert, (Type{Gtk.GdkEvent}, Ptr{Gtk.GdkEvent}),)
# 1 method for generic function "convert":
convert(::Type{T}, unbox::Ptr{T}) where T<:Gtk.GLib.GBoxed in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:287

despite the existence of this method.

Can be replicated with

convert(Gtk.GdkEvent, Gtk.GLib.GBoxedUnkown(C_NULL))

I initially wondered if it could be due to a method ambiguity, and there is indeed one in related methods, but fixing it (#312) doesn't solve this problem.

[timholy]

CC @vtjnash

[timholy]

This looks more and more like a method sorting bug (CC @JeffBezanson). Here's a list of methods(convert), edited to delete anything not defined in Gtk. (Obviously, the order is preserved.)

convert(::Type{Gtk.GLib.GBoxedUnkown}, boxed::Gtk.GLib.GBoxedUnkown) in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:281
convert(::Type{Gtk.GLib.GError}, err::Ptr{Gtk.GLib.GError}) in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gerror.jl:7
convert(::Type{Gtk.GdkRectangle}, rect::Ptr{Gtk.GdkRectangle}) in Gtk at /home/tim/.julia/v0.6/Gtk/src/gdk.jl:9
convert(::Type{Gtk.RGB}, x::Unsigned) in Gtk at /home/tim/.julia/v0.6/Gtk/src/displays.jl:14
convert(::Type{Gtk.RGBA}, x::Unsigned) in Gtk at /home/tim/.julia/v0.6/Gtk/src/displays.jl:21
convert(::Type{Gtk.GLib.GBoxed}, boxed::Gtk.GLib.GBoxed) in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:280
convert(::Type{T}, boxed::T) where T<:Gtk.GLib.GBoxed in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:282
convert(::Type{Gtk.GLib.GBoxed}, unbox::Ptr{Gtk.GLib.GBoxed}) in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:284
convert(::Type{T}, unbox::Ptr{T}) where T<:Gtk.GLib.GBoxed in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:287
convert(::Type{T}, ptr::Ptr{T}) where T<:Gtk.GLib.GObject in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:300
convert(::Type{Gtk.GdkEvent}, evt::Ptr{Gtk.GdkEvent}) in Gtk at /home/tim/.julia/v0.6/Gtk/src/gdk.jl:73
convert(::Type{Gtk.GLib.GBoxed}, unbox::Ptr{T}) where T<:Gtk.GLib.GBoxed in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:285
convert(::Type{Gtk.MatrixStrided}, img::Gtk.GdkPixbuf) in Gtk at /home/tim/.julia/v0.6/Gtk/src/displays.jl:251
convert(::Type{T}, boxed::Gtk.GLib.GBoxed) where T<:Gtk.GLib.GBoxed in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:283
convert(::Type{T}, unbox::Ptr{Gtk.GLib.GBoxed}) where T<:Gtk.GLib.GBoxed in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:286
convert(::Type{T}, w::Ptr{Gtk.GLib.GObject}) where T<:Gtk.GLib.GObject in Gtk.GLib at /home/tim/.julia/v0.6/Gtk/src/GLib/gtype.jl:297
convert(::Type{U}, x::Gtk.RGB) where U<:Unsigned in Gtk at /home/tim/.julia/v0.6/Gtk/src/displays.jl:15
convert(::Type{U}, x::Gtk.RGBA) where U<:Unsigned in Gtk at /home/tim/.julia/v0.6/Gtk/src/displays.jl:22
convert(::Type{P}, a::Gtk.MatrixStrided) where P<:Ptr in Gtk at /home/tim/.julia/v0.6/Gtk/src/displays.jl:145

Notice that the method at src/GLib/gtype.jl:287 is above the one at src/gdk.jl:73. (I'm using #312, your line numbers may differ.)

[timholy]

Should be fixed on Julia master (JuliaLang/julia#22162), but I'll leave this open until it's verified.

[lobingera]

julia master means: 0.7? Or is this 0.6.x backport?

[timholy]

master = 0.7. Keep an eye on that issue to see what the decision is re backporting.

[jpsamaroo]

This in indeed fixed on Julia 0.7 Master - the MWE I posted prints keys as expected now (once I add a nothing line after the @async line of course, since I forgot that initially - oops). Great detective work guys! Should we keep this issue open until the fix is backported to 0.6.x, or just close it?

[timholy]

I think we can close it, the backport is already part of JuliaLang/julia#22199. Thanks for checking!