On 27/03/2012 14:22, Terry Therneau wrote:
I received the following note this AM. The problem is, I'm not quite
sure how to fix it.
Can one use PROTECT(coxlist(eval(PROTECT.... , do I create an
intermediate variable, or otherwise?
You can, but I find it easiest to follow if you create an intermediate
variable. Look for example at unique.c:
SEXP call, r;
PROTECT(call = lang2(install("as.character"), s));
PROTECT(r = eval(call, env));
UNPROTECT(2);
return r;
I'm willing to update the code if someone will give me a pointer to the
right documentation. This particular chunk was written when there was a
lot of change going on in the callback mechanism and so there might be a
safer and/or simpler and/or more standard aproach by now. The routine in
question has to do with penalized Cox models, the C code needs to get
the value of the penalty and the penalty is an arbitrary S expression
passed down from top level.
Terry T
----------------------------
In survival_2.36-12 (and earlier), in the function cox_callback() at
cox_Rcallback.c:40:
PROTECT(coxlist=eval(lang2(fexpr,data),rho));
the return value of the call to lang2() is vulnerable if allocations
within eval() give rise to garbage collection.
(Discovered during CXXR development.)
Andrew
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--
Brian D. Ripley, [email protected]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
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