From ripley at stats.ox.ac.uk  Wed Apr 12 07:57:03 2006
From: ripley at stats.ox.ac.uk (Prof Brian Ripley)
Date: Wed, 12 Apr 2006 06:57:03 +0100 (BST)
Subject: [Rd] Stack checking, core dumps, and embedding R
In-Reply-To: <Pine.LNX.4.64.0604120640540.31187@gannet.stats.ox.ac.uk>
References: <1abe3fa90604110234v1b4958c0w1e51e2b49f7ff9c5@mail.gmail.com>
	<E725DDAC-4044-4A6E-B9F6-007FAF7225DA@r-project.org>
	<Pine.LNX.4.64.0604120640540.31187@gannet.stats.ox.ac.uk>
Message-ID: <Pine.LNX.4.64.0604120648590.31187@gannet.stats.ox.ac.uk>

On Wed, 12 Apr 2006, Prof Brian Ripley wrote:

> On Tue, 11 Apr 2006, Simon Urbanek wrote:
>
>> On Apr 11, 2006, at 5:34 AM, A.J. Rossini wrote:
>>
>>> I've been experiencing some interesting stack warnings recently
>>> when moving from R 2.2.x to the R 2.3.0 series and the R 2.4.0
>>> series.  In particular, I'm getting warnings of "Error: C stack
>>> usage is too close to the limit" before segfaulting, and this
>>> wasn't happening under the 2.2.x series.
>>>
>>> Here's the question statement:  (ONLY) In the situation where one
>>> is embedding R, is anyone else seeing this occur with recent (past
>>> 2 weeks) versions of R (both the 2.3.x and 2.4.x series)?
>>>
>>
>> When embedding R, the stack base is set to -1 (which is almost
>> certainly wrong) if R cannot find the stack base using some system
>> method.
>
> Setting it to -1 means stack checking is disabled, so _no_ harm is done.
> The test is
>
>     if(R_CStackLimit != -1 && usage > 0.95 * R_CStackLimit) {
>
> in errors.c.
>
>> I have just fixed the detection for OS X, so you shouldn't
>> get that message there anymore. However, I was wondering why to not
>> set it to something reasonable - even if we are not the main
>> application, IMHO less harm is done setting it to something based on
>> the current stack pointer than using -1. The status quo relies on the
>> embedding application to set the stack base - I don't know if that's
>> a good idea. Opinions?
>
> Wrong premise, wrong conclusion.

Sorry, I misunderstood this (we don't use 'base'): I guess you mean if 
R_CStackStart is unset, it defaults to -1.  In that case the intention was 
that R_CStackLimit be set to -1.  It seems that has dropped off, and I 
have reinstated it.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595



[Rd] Stack checking, core dumps, and embedding R
Prof Brian Ripley