trap formerly silent overflow in fisher.test()

git-svn-id: https://svn.r-project.org/R/trunk@87468 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: ripley

doc/NEWS.Rd

@@ -482,6 +482,10 @@
 
       \item \code{dir.create()} is protected against being passed an
       empty string as its \code{path} argument.
+
+      \item Silent integer overflow could occur in the
+       \sQuote{exact} computations for \code{fisher.test()} for
+       unrealistic inputs: this is now an error.
     }
   }
 }

src/library/stats/src/fexact.c

@@ -1444,6 +1444,8 @@ f5xact(double pastp, double tol, int *kval, int *key, int ldkey,
 	else if (stp[ipn] > test2)
 	    ipn = nr[ipn];
 	else {
+	    if (INT_MAX - ifrq[ipn] < ifreq)
+		Rf_error("integer overflow in exact computation");
 	    ifrq[ipn] += ifreq;
 	    return;
 	}