Function Rf_protect 

pub unsafe fn Rf_protect(s: SEXP) -> SEXP

Add a SEXP to the protect stack, preventing GC collection.

Cost: O(1) — single array write (R_PPStack[top++] = s). No allocation.

Must be balanced by a corresponding Rf_unprotect. The protect stack is LIFO — nested scopes are safe, but interleaved usage from different scopes will cause incorrect unprotection. Checked wrapper for Rf_protect. Calls Rf_protect_unchecked and routes through with_r_thread. Generated from source location line 2087, column 12. Generated from source file miniextendr-api/src/ffi.rs.