[Rd] PROTECT help

Terry Therneau
Tue, 27 Mar 2012 13:22:38 -0000

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?

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