1 files changed, 12 insertions, 0 deletions
diff --git a/boost/random/independent_bits.hpp b/boost/random/independent_bits.hpp
index dec63b3f46..cd2dd1f225 100644
--- a/boost/random/independent_bits.hpp
+++ b/boost/random/independent_bits.hpp
@@ -158,6 +158,18 @@ public:
 
         BOOST_ASSERT(n0*w0 + (n - n0)*(w0 + 1) == w);
 
+        BOOST_ASSERT((n == 1) == (w0 == w));
+
+        // special case to avoid undefined behavior from shifting
+        if(n == 1) {
+            BOOST_ASSERT(n0 == 1);
+            base_unsigned u;
+            do {
+                u = detail::subtract<base_result_type>()(_base(), (_base.min)());
+            } while(u > base_unsigned(y0 - 1));
+            return u & y0_mask;
+        }
+
         result_type S = 0;
         for(std::size_t k = 0; k < n0; ++k) {
             base_unsigned u;