check for String, and length one (closes #375)

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,8 @@
+2015-09-21  Dirk Eddelbuettel  <[email protected]>
+
+        * inst/include/Rcpp/String.h: Before assigning ensure we received
+        exactly one string argument
+
 2015-09-10  Dirk Eddelbuettel  <[email protected]>
 
         * DESCRIPTION: Release 0.12.1

inst/include/Rcpp/String.h

@@ -72,11 +72,19 @@ namespace Rcpp {
 
         /** construct a string from a single CHARSXP SEXP */
         String(SEXP charsxp) : data(charsxp), valid(true), buffer_ready(false), enc(Rf_getCharCE(charsxp)) {
-            Rcpp_PreserveObject( data );
+            if (! ::Rf_isString(data))
+                throw ::Rcpp::not_compatible("expecting a string");
+            if (::Rf_length(data) != 1)
+                throw ::Rcpp::not_compatible("expecting a single value");
+            Rcpp_PreserveObject(data);
             RCPP_STRING_DEBUG( "String(SEXP)" ) ;
         }
 
         String(SEXP charsxp, const std::string& enc) : data(charsxp), valid(true), buffer_ready(false) {
+            if (! ::Rf_isString(data))
+                throw ::Rcpp::not_compatible("expecting a string");
+            if (::Rf_length(data) != 1)
+                throw ::Rcpp::not_compatible("expecting a single value");
             Rcpp_PreserveObject( data );
             set_encoding(enc);
             RCPP_STRING_DEBUG( "String(SEXP)" ) ;