Safer duplicate for STRSXPs without STRING_PTR.

git-svn-id: https://svn.r-project.org/R/trunk@89005 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: luke

src/main/duplicate.c

@@ -348,10 +348,19 @@ static SEXP duplicate1(SEXP s, Rboolean deep)
     case CPLXSXP: DUPLICATE_ATOMIC_VECTOR(Rcomplex, COMPLEX, COMPLEX_RO, t, s, deep); break;
     case RAWSXP: DUPLICATE_ATOMIC_VECTOR(Rbyte, RAW, RAW_RO, t, s, deep); break;
     case STRSXP:
-	/* direct copying and bypassing the write barrier is OK since
-	   t was just allocated and so it cannot be older than any of
-	   the elements in s.  LT */
-	DUPLICATE_ATOMIC_VECTOR(SEXP, STRING_PTR, STRING_PTR_RO, t, s, deep);
+	/* Direct copying and bypassing the write barrier would be OK
+	   since t was just allocated and so it cannot be older than
+	   any of the elements in s. But it does not increment the
+	   reference counts, so use a loop with SET_STRING_ELT. LT */
+	//DUPLICATE_ATOMIC_VECTOR(SEXP, STRING_PTR, STRING_PTR_RO, t, s, deep);
+	n = XLENGTH(s);
+	PROTECT(s);
+	PROTECT(t = allocVector(TYPEOF(s), n));
+	for(i = 0 ; i < n ; i++)
+	    SET_STRING_ELT(t, i, STRING_ELT(s, i));
+	DUPLICATE_ATTRIB(t, s, deep);
+	COPY_TRUELENGTH(t, s);
+	UNPROTECT(2);
 	break;
     case PROMSXP:
 	return s;