Avoid ATTRIB under R 4.6.0 and use R_mapAttrib

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,12 @@
+2025-12-21  Dirk Eddelbuettel  <[email protected]>
+
+	* inst/include/Rcpp/DataFrame.h (nrow): Rewritten using R_mapAttrib()
+	avoiding ATTRIB() likely to be removed by R 4.6.0
+	* inst/include/Rcpp/proxy/AttributeProxy.h (attributeNames): Idem
+	* src/utilities.cpp: Add two helper functions used by R_mapAttrib()
+	* inst/include/Rcpp/routines.h: Register two new helper functions
+	* src/rcpp_init.cpp (registerFunctions): Idem
+
 2025-12-19  Dirk Eddelbuettel  <[email protected]>
 
 	* man/RcppUnitTests.Rd: Removed outdated help page

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: Rcpp
 Title: Seamless R and C++ Integration
-Version: 1.1.0.11
-Date: 2025-12-17
+Version: 1.1.0.11.2
+Date: 2025-12-21
 Authors@R: c(person("Dirk", "Eddelbuettel", role = c("aut", "cre"), email = "[email protected]",
                     comment = c(ORCID = "0000-0001-6419-907X")),
              person("Romain", "Francois", role = "aut",

inst/include/Rcpp/DataFrame.h

@@ -67,6 +67,15 @@ namespace Rcpp{
         // compact form thereby allocating a huge vector when we just want
         // the row.names. Hence this workaround.
         inline int nrow() const {
+#if R_VERSION >= R_Version(4, 6, 0)
+            SEXP v = R_mapAttrib(Parent::get__(), get_row_count, R_NilValue);
+            if (v != NULL && TYPEOF(v) == INTSXP) {
+                return INTEGER(v)[0];
+            } else {
+                // TODO: error?
+                return NA_INTEGER;
+            }
+#else
             SEXP rn = R_NilValue ;
             SEXP att = ATTRIB( Parent::get__() )  ;
             while( att != R_NilValue ){
@@ -81,9 +90,10 @@ namespace Rcpp{
             if (TYPEOF(rn) == INTSXP && LENGTH(rn) == 2 && INTEGER(rn)[0] == NA_INTEGER)
                 return std::abs(INTEGER(rn)[1]);
             return LENGTH(rn);
+#endif
         }
 
-	template <typename T>
+        template <typename T>
         void push_back( const T& object){
             Parent::push_back(object);
             set_type_after_push();

inst/include/Rcpp/proxy/AttributeProxy.h

@@ -78,16 +78,25 @@ class AttributeProxyPolicy {
     }
 
     std::vector<std::string> attributeNames() const {
-        std::vector<std::string> v ;
+        std::vector<std::string> v;
+#if R_VERSION >= R_Version(4, 6, 0)
+        R_mapAttrib(static_cast<const CLASS&>(*this).get__(), get_attr_names, (void *) &v);
+#else
         SEXP attrs = ATTRIB( static_cast<const CLASS&>(*this).get__());
         while( attrs != R_NilValue ){
             v.push_back( std::string(CHAR(PRINTNAME(TAG(attrs)))) ) ;
             attrs = CDR( attrs ) ;
         }
+#endif
         return v ;
     }
 
     bool hasAttribute( const std::string& attr) const {
+#if R_VERSION >= R_Version(4, 6, 0)
+        std::vector<std::string> v = attributeNames();
+        auto it = std::find(v.begin(), v.end(), attr);
+        return it != v.end();   // if found 'it' points to element equal to 'attr'
+#else
         SEXP attrs = ATTRIB(static_cast<const CLASS&>(*this).get__());
         while( attrs != R_NilValue ){
             if( attr == CHAR(PRINTNAME(TAG(attrs))) ){
@@ -96,6 +105,7 @@ class AttributeProxyPolicy {
             attrs = CDR( attrs ) ;
         }
         return false; /* give up */
+#endif
     }
 
 

inst/include/Rcpp/routines.h

@@ -74,6 +74,8 @@ SEXP          reset_current_error();
 int           error_occured();
 SEXP          rcpp_get_current_error();
 // void          print(SEXP s);
+SEXP          get_attr_names(SEXP t, SEXP a, void* d);
+SEXP          get_row_count(SEXP t, SEXP a, void* d);
 
 #else
 
@@ -309,6 +311,19 @@ inline attribute_hidden SEXP rcpp_get_current_error(){
 //     fun(s);
 // }
 
+inline attribute_hidden SEXP get_attr_names(SEXP tag, SEXP attr, void* data){
+    typedef SEXP (*Fun)(SEXP, SEXP, void*);
+    static Fun fun = GET_CALLABLE("get_attr_names");
+    return fun(tag, attr, data);
+}
+
+inline attribute_hidden SEXP get_row_count(SEXP tag, SEXP attr, void* data){
+    typedef SEXP (*Fun)(SEXP, SEXP, void*);
+    static Fun fun = GET_CALLABLE("get_row_count");
+    return fun(tag, attr, data);
+}
+
+
 #endif
 
 

src/rcpp_init.cpp

@@ -127,6 +127,9 @@ void registerFunctions(){
     RCPP_REGISTER(Rcpp_precious_remove)
     RCPP_REGISTER(Rcpp_cout_get)
     RCPP_REGISTER(Rcpp_cerr_get)
+
+    RCPP_REGISTER(get_attr_names)
+    RCPP_REGISTER(get_row_count)
     #undef RCPP_REGISTER
 }
 

src/utilities.cpp

@@ -0,0 +1,54 @@
+// utilities.cpp: Rcpp R/C++ interface class library -- attribute utilities
+//
+// Copyright (C) 2025 - current  Dirk Eddelbuettel
+//
+// This file is part of Rcpp.
+//
+// Rcpp is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 2 of the License, or
+// (at your option) any later version.
+//
+// Rcpp is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Rcpp.  If not, see <http://www.gnu.org/licenses/>.
+
+#define COMPILING_RCPP
+
+#include <vector>
+#include <string>
+#include <Rcpp/Lighter>
+
+// See WRE Section 6.22.6 'Working with attributes' under R 4.6.0 or later
+// This function collects the names from 'tag' in a vector passed via *data
+// It is used by AttributeProxyPolicy::attributeNames() in a call to R_mapAttrib
+// [[Rcpp::register]]
+SEXP get_attr_names(SEXP tag, SEXP attr, void* data) {
+    std::vector<std::string>* vecptr = static_cast<std::vector<std::string>*>(data);
+    std::string s{CHAR(Rf_asChar(tag))};
+    vecptr->push_back(s);
+    return NULL;
+}
+
+// See WRE Section 6.22.6 'Working with attributes' under R 4.6.0 or later
+// This function extract the number of rows in a data frame
+// It is used DataFrame_impl::nrow() in a call to R_mapAttrib()
+// [[Rcpp::register]]
+SEXP get_row_count(SEXP tag, SEXP attr, void* data) {
+    if (tag == R_RowNamesSymbol) {
+        if (TYPEOF(attr) == INTSXP && LENGTH(attr) == 2 && INTEGER(attr)[0] == NA_INTEGER) {
+            int n = std::abs(INTEGER(attr)[1]);
+            //Rcpp::Rcout << "Seeing " << n << std::endl;
+            return Rf_ScalarInteger(n);
+        }
+        if (Rf_isNull(attr)) {
+            return Rf_ScalarInteger(0);
+        }
+        return Rf_ScalarInteger(LENGTH(attr));
+    }
+    return NULL;
+}