Spurious fire from timer
1 view (last 30 days)
Show older comments
Question: Has anyone experienced the behavior, which I describe here?
Posting questions here makes me think. This is a better version of Weird behavior when debugging code invoked by timer.
I argue that it happens that a callback is spuriously fired during debugging of code invoked by a timer. Now, I think I have a way to demonstrate the behavior; that is to reproduce the behavior.
Recipe:
- R2012a 64bit, Win7
- put a break-point in the subfunction, index_out_of_bounds, at line 7
- start the function, spurious_fire_from_timer
- at the break-point execute stk1 = dbstack;
- open an m-file in the editor
- at the break-point execute stk2 = dbstack;
- inspect the stack-drop-down-list
- run whos and {stk2.name}'
- click [Continue] (/F5)
- run whos and {stk1.name}'
K>> whos
Name Size Bytes Class Attributes
a 1x1 8 double
stk2 10x1 4164 struct
Note that stk1 is not in this workspace and display the function names
K>> {stk2.name}'
ans =
'index_out_of_bounds'
'invoked_by_timer'
'timercb'
'timercb'
'index_out_of_bounds'
'invoked_by_timer'
'timercb'
'timercb'
'wait'
'spurious_fire_from_timer'
[Continue] shows
Error while evaluating TimerFcn for timer 'my_timer'
Index exceeds matrix dimensions.
and takes us back to the first break. Now, stk1 is in the current workspace
K>> whos
Name Size Bytes Class Attributes
a 1x1 8 double
stk1 6x1 2582 struct
K>> {stk1.name}'
ans =
'index_out_of_bounds'
'invoked_by_timer'
'timercb'
'timercb'
'wait'
'spurious_fire_from_timer'
K>>
Comments:
- This shows that opening an m-file caused Matlab to fire a callback.
- I think this can be triggered by other user actions as well. However, I'm not sure which or whether it is intermittent.
- While experimenting with this behavior yesterday Matlab once crashed "without smoke"; just dropped dead without any crash report.
- This behavior does not occur (i.e. I failed to make it happen) with 'ExecutionMode' equal to 'singleShot'
where
function spurious_fire_from_timer()
tmr = timer('Name' , 'my_timer' ...
, 'TimerFcn' , @invoked_by_timer ...
, 'BusyMode' , 'drop' ...
, 'ExecutionMode' , 'fixedRate' ...
, 'Period' , 1 ...
, 'StartDelay' , 1 ...
, 'TasksToExecute', 1 ...
);
start( tmr )
wait ( tmr )
end
and
function invoked_by_timer( tmr, evnt )
index_out_of_bounds()
variable_not_used( tmr, evnt )
end
function index_out_of_bounds()
a = 17;
b = 18;
c = a(2);
variable_not_used( a, b, c )
end
and
function variable_not_used( varargin )
% variable_not_used - helps keep the code analyzer box green
end
2 Comments
Tom Shlomo
on 5 Feb 2019
I experience the same problem with MATLAB 2018b, WIN10
Any chance you managed to solve this?
Answers (0)
See Also
Categories
Find more on Debugging and Analysis in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!