cpp_register(): add use_package parameter

so that the generated wrapper code calls C++ functions as
.Call("func", ..., PACKAGE="pkg")

R/register.R

@@ -7,6 +7,8 @@
 #' In order to use `cpp_register()` the `cli`, `decor`, `desc`, `glue`,
 #' `tibble` and `vctrs` packages must also be installed.
 #' @param path The path to the package root directory
+#' @param use_package If `TRUE`, uses `.Call("yourfunc", ..., PACKAGE="yourpackage")`
+#'        to call C++ functions, otherwise (the default) uses ``.Call(`yourfunc`, ...)``.
 #' @param quiet If `TRUE` suppresses output from this function
 #' @return The paths to the generated R and C++ source files (in that order).
 #' @export
@@ -31,7 +33,7 @@
 #'
 #' # cleanup
 #' unlink(dir, recursive = TRUE)
-cpp_register <- function(path = ".", quiet = FALSE) {
+cpp_register <- function(path = ".", use_package = FALSE, quiet = FALSE) {
   stop_unless_installed(get_cpp_register_needs())
 
   r_path <- file.path(path, "R", "cpp11.R")
@@ -56,7 +58,7 @@ cpp_register <- function(path = ".", quiet = FALSE) {
 
   init <- generate_init_functions(get_registered_functions(all_decorations, "cpp11::init", quiet))
 
-  r_functions <- generate_r_functions(funs, package, use_package = FALSE)
+  r_functions <- generate_r_functions(funs, package, use_package = use_package)
 
   dir.create(dirname(r_path), recursive = TRUE, showWarnings = FALSE)
 
@@ -102,6 +104,8 @@ cpp_register <- function(path = ".", quiet = FALSE) {
 
   extra_includes <- paste0(extra_includes, collapse = "\n")
 
+  forceSymbols = if (use_package) "" else "\n        R_forceSymbols(dll, TRUE);"
+
   brio::write_lines(path = cpp_path, glue::glue('
       // Generated by cpp11: do not edit by hand
       // clang-format off
@@ -118,8 +122,7 @@ cpp_register <- function(path = ".", quiet = FALSE) {
       {init$declarations}
       extern "C" attribute_visible void R_init_{package}(DllInfo* dll){{
         R_registerRoutines(dll, NULL, CallEntries, NULL, NULL);
-        R_useDynamicSymbols(dll, FALSE);{init$calls}
-        R_forceSymbols(dll, TRUE);
+        R_useDynamicSymbols(dll, FALSE);{init$calls}{forceSymbols}
       }}
       ',
       call_entries = glue::glue_collapse(call_entries, "\n")