Why stack overflow with such a small stack?

Kenneth McDonald · Aug 30, 2007

I'm getting the following error:

sheet.rb:35:in `values': stack level too deep (SystemStackError)
from sheet.rb:35:in `values'
from sheet.rb:53:in `to_s'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `map'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `map'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `map'
from sheet.rb:52:in `to_s'
from sheet.rb:92

The output above is given _in full_. Is Ruby truncating the call stack
in this output? If so, how I can I see a larger snapshot of the stack,
so I can trace down where the infinite recursion is really happening? If
not, why am I getting this error?

Thanks,
Ken

Daniel DeLorme · Aug 31, 2007

Kenneth said:
I'm getting the following error:

sheet.rb:35:in `values': stack level too deep (SystemStackError)
from sheet.rb:35:in `values'
from sheet.rb:53:in `to_s'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `map'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `map'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `to_s'
from sheet.rb:52:in `map'
from sheet.rb:52:in `to_s'
from sheet.rb:92

The output above is given _in full_. Is Ruby truncating the call stack
in this output? If so, how I can I see a larger snapshot of the stack,
so I can trace down where the infinite recursion is really happening? If
not, why am I getting this error?

Here's one even shorter:SystemStackError: stack level too deep
from (irb):2:in `x'
from (irb):2:in `x'
from (irb):4

Pretty smart of ruby to avoid a gazillion lines of identical output IMHO

Daniel

Kenneth McDonald · Aug 31, 2007

Daniel said:
Here's one even shorter:
SystemStackError: stack level too deep
from (irb):2:in `x'
from (irb):2:in `x'
from (irb):4

Pretty smart of ruby to avoid a gazillion lines of identical output IMHO

Daniel

To a newcomer, it's sorta nonobvious, however--it turned out the problem
was that I'd made a circular reference to 'values' instead of '@values',
and the fact that the stack was full of 'values' frames is certainly not
obvious from the above.

Ken

Michael T. Richter · Aug 31, 2007

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To a newcomer, it's sorta nonobvious, however--it turned out the problem=20
was that I'd made a circular reference to 'values' instead of '@values',=20
and the fact that the stack was full of 'values' frames is certainly not=20
obvious from the above.

A good rule of thumb for avoiding this problem is to name your classes
and your variables after nouns and your methods after verbs.

So instead of having a method "values" that uses the member "@values" --
something pretty much guaranteed to lead to trauma at some point down
the road -- make a method "get_values" or "set_values" or
"initialize_values" or whatever that uses a member called @values.

--=20
Michael T. Richter <[email protected]> (GoogleTalk:
(e-mail address removed))
Experts in advanced countries underestimate by a factor of two to four
the ability of people in underdeveloped countries to do anything
technical. (Charles P Issawi)

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On Fri, 2007-31-08 at 10:35 +0900, Kenneth McDonald wrote:
<BLOCKQUOTE TYPE=3DCITE>
<PRE>
To a newcomer, it's sorta nonobvious, however--it t=
urned out the problem 
was that I'd made a circular reference to 'values' =
instead of '@values', 
and the fact that the stack was full of 'values' fr=
ames is certainly not 
obvious from the above.
</PRE>
</BLOCKQUOTE>
 
A good rule of thumb for avoiding this problem is to name your classes and =
your variables after nouns and your methods after verbs. 
 
So instead of having a method "values" that uses the member &quot=
;@values" -- something pretty much guaranteed to lead to trauma at som=
e point down the road -- make a method "get_values" or "set_=
values" or "initialize_values" or whatever that uses a membe=
r called @values. 
 
<TABLE CELLSPACING=3D"0" CELLPADDING=3D"0" WIDTH=3D"100%">
<TR>
<TD>
-- 
Michael T. Richter <<A HREF=3D"mailto:[email protected]">ttmri=
(e-mail address removed)</A>> (GoogleTalk: (e-mail address removed)) 
Experts in advanced countries underestimate by a factor of two to four t=
he ability of people in underdeveloped countries to do anything technical. =
(Charles P Issawi)
</TD>
</TR>
</TABLE>
</BODY>
</HTML>

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Robert Klemme · Aug 31, 2007

A good rule of thumb for avoiding this problem is to name your classes
and your variables after nouns and your methods after verbs.

So instead of having a method "values" that uses the member "@values" --
something pretty much guaranteed to lead to trauma at some point down
the road -- make a method "get_values" or "set_values" or
"initialize_values" or whatever that uses a member called @values.

Although I agree in general (i.e. using verbs for method names) I
heavily disagree with your last advice: according to Ruby's convention a
getter is named "foo" and a setter "foo=". This is implemented in attr*
methods and IMHO it is not advisable to leave this convention.

Also, there are good reasons to use getters instead of instance
variables, namely that you get more abstraction (there doesn't
necessarily have to be a member variable of that name).

Kind regards

robert

Kyle Schmitt · Aug 31, 2007

Heh, This is one of the few languages I haven't had that happen to to
me on before.

Lisp, C, C++, Perl... but I haven't caused one of those on _ruby_ before.

Now, if you've really intended to do recursion, try making it tail recursive.

Err... Ruby does optimize for tail recursion, right?

--Kyle

Jano Svitok · Aug 31, 2007

Heh, This is one of the few languages I haven't had that happen to to
me on before.

Lisp, C, C++, Perl... but I haven't caused one of those on _ruby_ before.

Now, if you've really intended to do recursion, try making it tail recursive.

Err... Ruby does optimize for tail recursion, right?

I'm not sure, after some googling it seems that 1.8 doesn't and YARV
might partially optimize.

Kenneth McDonald · Sep 1, 2007

Unless I read otherwise, I usually assume that languages don't optimize
tail recursion. If you look at typical codebases, using tail recursion
instead of some sort of higher-level looping construct, or even a simple
basic loop, is really an academic curiosity. It doesn't normally make
code clearer or easier to write, and most people, even those who are
aware of it, don't use it. (In fact people who really know about it
often tend to avoid it because they also know of the overhead induced by
function calling.) So why bother optimizing for this case?

Ken

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Why stack overflow with such a small stack?

Kenneth McDonald

Daniel DeLorme

Kenneth McDonald

Michael T. Richter

Robert Klemme

Kyle Schmitt

Jano Svitok

Kenneth McDonald

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