R devel - Feb 2008 - minor bug and patch: attr(x, "names")<-y when y is a pairlist (PR#10807)

Full_Name: John Brzustowski
Version: R-devel trunk and R 2.4.0
OS: linux
Submission from: (NULL) (76.10.152.79)


# Bug: 
> x<-1:3
> attr(x, "names")<-pairlist("a", "b",
"c")
> x
a a a 
1 2 3 
# Note that the simpler alternative does work:
> names(x)<-pairlist("a", "b", "c")
> x
a b c 
1 2 3 

# After applying the patch:
> x<-1:3
> attr(x, "names")<-pairlist("a", "b",
"c")
> x
a b c 
1 2 3 

# The problem is in src/main/attrib.c: namesgets(), where
# the pointer to the pairlist of names is not advanced.

# Here is a simple patch against R-devel trunk.  A cleaner
# but more complicated approach would be 
# to refactor namesgets() and do_namesgets().
#
# Note that the name list need not be as long as the LHS,
# because subsequent code pads the name list with NAs, if needed.

 Index: trunk/src/main/attrib.c
==================================================================---
trunk/src/main/attrib.c	(revision 44547)
+++ trunk/src/main/attrib.c	(working copy)
@@ -681,7 +681,7 @@
 SEXP namesgets(SEXP vec, SEXP val)
 {
     int i;
-    SEXP s, rval;
+    SEXP s, rval, tval;
 
     PROTECT(vec);
     PROTECT(val);
@@ -695,8 +695,8 @@
 	else {
 	    rval = allocVector(STRSXP, length(vec));
 	    PROTECT(rval);
-	    for (i = 0; i < length(vec); i++) {
-		s = coerceVector(CAR(val), STRSXP);
+	    for (i = 0, tval=val; i < length(vec) && tval != R_NilValue;
i++,
tval=CDR(tval)) {
+		s = coerceVector(CAR(tval), STRSXP);
 		SET_STRING_ELT(rval, i, STRING_ELT(s, 0));
 	    }
 	    UNPROTECT(1);