Timing of SET_VECTOR_ELT
On Apr 1, 2013, at 1:10 PM, Terry Therneau wrote:
Assume a C program invoked by .Call, that returns a list. Near the top of the program we allocate space for all the list elements. (It is my habit to use "xyz2" for the name of the R object and "xyz" for the pointer to its contents.) PROTECT(means2 = allocVector(REALSXP, nvar)); means = REAL(means2); PROTECT(u2 = allocVector(REALSXP, nvar)); u = REAL(u2); PROTECT(loglik2 = allocVector(REALSXP, 2)); loglik = REAL(loglik2); PROTECT(rlist = mknamed(VECSXP, outnames)); Can I assign the individual elements into rlist using SET_VECTOR_ELT at this point, or do I need to wait until the end of the program, after I've filled in means[i], u[i], etc.? I likely depends on whether I'm assigning a pointer or a copy.
You're assigning a pointer, so it doesn't matter. FWIW, you can avoid all the PROTECTion mess if you alloc+assign, e.g. SEXP rlist = PROTECT(mknamed(VECSXP, outnames)); SEXP means = SET_VECTOR_ELT(rlist, 0, allocVector(REALSXP, nvar)); ... since you only need to protect the parent object. Cheers, Simon