Improved backports for resizable API from Ivan Krylov.

git-svn-id: https://svn.r-project.org/R/trunk@89097 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: luke

doc/manual/R-exts.texi

@@ -17818,9 +17818,23 @@ void CLEAR_ATTRIB(SEXP x)
 #if R_VERSION < R_Version(4, 6, 0)
 # define DATAPTR_RW(x) DATAPTR(x)
 # define R_class(x) R_data_class(x, FALSE)
-# define R_allocResizableVector(type, maxlen) Rf_allocVector(type, naxlen)
-# define R_duplicateAsResizable(x) duplicate(x)
-# define R_resizeVector(x, newlen) SETLENGTH(x, n)
+# define R_resizeVector(x, newlen) SETLENGTH(x, newlen)
+
+SEXP R_allocResizableVector(SEXPTYPE type, R_xlen_t maxlen)
+@{
+    SEXP ret = Rf_allocVector(type, maxlen);
+    SET_TRUELENGTH(ret, maxlen);
+    SET_GROWABLE_BIT(ret);
+    return ret;
+@}
+
+SEXP R_duplicateAsResizable(SEXP x)
+@{
+    SEXP ret = Rf_duplicate(x);
+    SET_TRUELENGTH(ret, Rf_xlength(x));
+    SET_GROWABLE_BIT(ret);
+    return ret;
+@}
 #endif
 @end example