Mark values returned by active binding functions as not mutable to

prevent unintended mutation in complex assignments.


git-svn-id: https://svn.r-project.org/R/trunk@89121 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: luke

doc/NEWS.Rd

@@ -423,6 +423,10 @@
       \item \code{model.frame(~1, list(), na.action=na.pass)} and similar
       \dQuote{border-line} uses no longer produce invalid data frames,
       fixing \PR{18977}, reported with patch by \I{Mikael Jagan}.
+
+      \item Values returned by active binding functions are now marked as
+      not mutable to prevent unintended mutation in complex assignment
+      operations.
     }
   }
 }

src/main/envir.c

@@ -167,6 +167,8 @@ static SEXP getActiveValue(SEXP fun)
     PROTECT(expr);
     expr = eval(expr, R_GlobalEnv);
     UNPROTECT(1);
+    /* mark unmutable to prevent mutations in complex assignments */
+    MARK_NOT_MUTABLE(expr);
     return expr;
 }
 

tests/reg-tests-1e.R

@@ -2400,6 +2400,13 @@ stopifnot(chk0(structure(.Date   (numeric()), foobar = list(Dt = "A"))),
           chk0(structure(.POSIXct(numeric()), foobar = list(ct = "C"))))
 ## in R <= 4.5.2, give.attr=FALSE was not obeyed for 0-length "Date" / "POSIXt"
 
+## guard against mutation through active bindings
+y <- 1 + 0
+if (exists("x")) rm(x)
+makeActiveBinding("x", function(v) y, .GlobalEnv)
+x[1] <- 2
+stopifnot(y == 1)
+rm(x)
 
 
 ## keep at end