PROTECT help

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