# Error messages from Gtk callbacks are not being shown
**URL:** https://discourse.julialang.org/t/error-messages-from-gtk-callbacks-are-not-being-shown/38412
**Category:** General Usage
**Created:** [April 29, 2020, 8:18am UTC](https://discourse.julialang.org/t/error-messages-from-gtk-callbacks-are-not-being-shown/38412 "2020-04-29T08:18:43Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@xor0110](https://discourse.julialang.org/u/xor0110)
#### Post date: [April 29, 2020, 8:18am UTC](https://discourse.julialang.org/t/error-messages-from-gtk-callbacks-are-not-being-shown/38412/1 "2020-04-29T08:18:43Z")
I’m developing a Gkt.jl application, and errors that happen inside a callback are not being displayed. For example, if you run this code and click the button multiple times:
```julia
using Gtk
w = Gtk.Window()
b = Gtk.Button("hello")
push!(w, b)
x = 0
signal_connect(b, "clicked") do widget
global x += 1
@info "hi $x"
@show 32 ÷ (3 - x)
end
Gtk.showall(w)
```
You’ll see this:
```julia
julia> include("/home/user/errtest.jl");
julia> [ Info: hi 1
32 ÷ (3 - x) = 16
[ Info: hi 2
32 ÷ (3 - x) = 32
[ Info: hi 3
[ Info: hi 4
32 ÷ (3 - x) = -32
```
I understand that Julia sometimes defaults to hiding error messages from secondary threads. Is this something related, or is this specific to Gtk? Is it a bug or a feature? I find it strange because in some situations I do get to see error messages. Would that mean the code was running in the main thread?
I get it that sometimes this behavior is the best, and that forcing every error message to be printed may even be challenging to do. I would absolutely love to see all my error messages, though, since it does not help me when something is not working and I cannot get a clue that it was caused just by a silly typo in a function call, for instance.
What can I do to be able to see all the error messages I may get from every thread in my Gtk.jl application?
---
### Author:  [@pixel27](https://discourse.julialang.org/u/pixel27)
#### Post date: [April 29, 2020, 7:38pm UTC](https://discourse.julialang.org/t/error-messages-from-gtk-callbacks-are-not-being-shown/38412/2 "2020-04-29T19:38:30Z")
I ran into this issue when I first started playing with Julia. What I ended up doing was created a function:
```julia
function log_exception(ex, stack)
local buffer = IOBuffer()
showerror(buffer, ex)
write(buffer, "\n\n")
for bt in stacktrace(stack)
showerror(buffer, bt)
write(buffer, '\n')
end
seekstart(buffer)
println(read(buffer, String))
end
```
Then in ALL my callbacks did:
```julia
try
# Call back code
catch ex
log_exception(ex, catch_backtrace())
end
```
I did this back when I first started playing with Julia. So the `println(read(buffer, String))` can probably be optimized to `println(take!(buffer))` in the log\_exception function. And a macro could probably be created to do the try/catch.
---
### Author:  [@xor0110](https://discourse.julialang.org/u/xor0110)
#### Post date: [May 4, 2020, 9:47am UTC](https://discourse.julialang.org/t/error-messages-from-gtk-callbacks-are-not-being-shown/38412/3 "2020-05-04T09:47:28Z")
Thanks so much @pixel27, this is very helpful. Indeed, looks like it could be a useful macro.
I imagine many programmers should feel the same need. I’m not sure how we could take this upstream, though.
---
### Author:  [@xor0110](https://discourse.julialang.org/u/xor0110)
#### Post date: [June 22, 2020, 3:27pm UTC](https://discourse.julialang.org/t/error-messages-from-gtk-callbacks-are-not-being-shown/38412/4 "2020-06-22T15:27:26Z")
I finally got to writing that macro. What’s a good place to submit this? Gtk.jl? Julia itself? Maybe it will just live on forever as a hacky snippet on discourse…
```julia
"Catches failures and prints a backtrace, the \"normal\" behavior that is sometimes suppressed in Julia"
macro printbt(f)
f.args[2] = quote
try
$(f.args[2])
catch ex
stack = catch_backtrace()
local buffer = IOBuffer()
showerror(buffer, ex)
write(buffer, "\n\n")
for bt in stacktrace(stack)
showerror(buffer, bt)
write(buffer, '\n')
end
seekstart(buffer)
println(read(buffer, String))
end
end
f
end
```