Also give better reporting for error-on-execution

src/GLib/signals.jl

@@ -88,7 +88,7 @@ function GClosureMarshal(closuref, return_value, n_param_values,
         end
     end
     local retval = nothing
-    g_siginterruptible() do
+    g_siginterruptible(cb) do
         # note: make sure not to leak any of the GValue objects into this task switch, since many of them were alloca'd
         retval = cb(params...) # widget, args...
     end
@@ -98,18 +98,22 @@ function GClosureMarshal(closuref, return_value, n_param_values,
             try
                 return_value[] = gvalue(retval)
             catch
-                if isgeneric(cb)
-                    warn("Executing ", cb, ":")
-                else
-                    warn("Executing ", Base.uncompressed_ast(cb.code).args[3].args[1])   # just show file/line
-                end
+                blame(cb)
                 error("Error setting return value of type $(typeof(retval)); did your callback return an unintentional value?")
             end
         end
     end
     return nothing
 end
 
+function blame(cb)
+    if isgeneric(cb)
+        warn("Executing ", cb, ":")
+    else
+        warn("Executing ", Base.uncompressed_ast(cb.code).args[3].args[1])   # just show file/line
+    end
+end
+
 # Signals API for the cb pointer
 # Gtk 2
 #   https://developer.gnome.org/gtk2/stable/GObject.html#GObject-destroy
@@ -210,7 +214,7 @@ else
     _get_return() = current_task().last
 end
 
-function g_siginterruptible(f::Base.Callable)
+function g_siginterruptible(f::Base.Callable, cb)
     global g_sigatom_flag, gtk_stack, gtk_work
     prev = g_sigatom_flag
     @assert prev $ (current_task() !== gtk_stack)
@@ -280,6 +284,7 @@ function g_siginterruptible(f::Base.Callable)
             end
         end
     catch err
+        blame(cb)
         ct = current_task()
         filter!(x->x!==ct, Base.Workqueue)
         if f !== yield
@@ -387,7 +392,7 @@ function uv_dispatch{T}(src::Ptr{Void},callback::Ptr{Void},data::T)
 end
 
 function g_yield(data)
-    g_siginterruptible(yield)
+    g_siginterruptible(yield, yield)
     return int32(true)
 end