[Rd] When collected warnings exceeds 50

[Prof Brian Ripley]

Fixed (in a different way) in R-devel/R-patched.

On Thu, 10 Nov 2011, Jeffrey Horner wrote:

> On Thu, Nov 10, 2011 at 10:54 PM, Jeffrey Horner
> <jeffrey.horner at gmail.com> wrote:
>> Hi,
>>
>> I've been tracking down a memory leak in an rApache application,
>> http://data.vanderbilt.edu/rapache/bbplot. The code was deployed in
>> 2007 and has survived numerous upgrades of both R and rApache
>> (including upgrades and bugs in RMySQL). It's written in such a way so
>> that web crawlers will download every possible URL the app will
>> create. It's not a high-traffic app, but just about every line of code
>> is executed at some point during a crawl by Google, Bing, etc.
>>
>> Here's the salient point: the app (well, just about all rApache apps)
>> sets option warn to 0 to collect all warnings until a request is
>> completed. It turns out that some requests will collect more than 50
>> warnings, and the result is an apache process that leaks memory until
>> finally seg faulting somewhere in one of R's extra packages, if I
>> recall correctly.
>>
>> After what seems like a month working on this problem, I think I've
>> narrowed it down to a simple test case. I'm testing with R-devel
>> r57624 on ubuntu linux. Running the following under valgrind:
>>
>> R -d valgrind
>>> options(warn=0)
>>> for (i in 1:51) factor(1,levels=c(1,1) # duplicate level warningcall
>
> Missed a closing parenthesis. should be :
>
>> options(warn=0)
>> for (i in 1:51) factor(1,levels=c(1,1)) # duplicate level warningcall
>
>>
>> and you should see "Invalid read" messages. I've narrowed it down to
>> vwarningcall_dflt starting a new R context via begincontext()  but
>> returning early without calling endcontext() in errors.c:
>>
>>  svn diff src/main/errors.c
>> Index: src/main/errors.c
>> ===================================================================
>> --- src/main/errors.c   (revision 57624)
>> +++ src/main/errors.c   (working copy)
>> @@ -333,8 +333,11 @@
>>        char *tr; int nc;
>>        if(!R_CollectWarnings)
>>            setupwarnings();
>> -       if( R_CollectWarnings > 49 )
>> +       if( R_CollectWarnings > 49 ) {
>> +           endcontext(&cntxt);
>> +           inWarning = 0;
>>            return;
>> +       }
>>        SET_VECTOR_ELT(R_Warnings, R_CollectWarnings, call);
>>        Rvsnprintf(buf, min(BUFSIZE, R_WarnLength+1), format, ap);
>>        if(R_WarnLength < BUFSIZE - 20 && strlen(buf) == R_WarnLength)
>>
>> This fix eliminates the "Invalid read" errors, but I'm unsure if it
>> fixes my application. I'll find out tomorrow.
>>
>> Jeff
>>
>
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>

-- 
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