commit 5beb2c3ab3df9b2f76b0c9d10db18c73c3ee5a2f
author Marshall Clow <mclow.lists@gmail.com> Wed Sep 20 17:34:11 2017
committer Marshall Clow <mclow.lists@gmail.com> Wed Sep 20 17:34:11 2017
tree 1ba66eae4f59866aa7d08dc4528cfbce8e1e28ae
parent 92687d45db566cdc47905555ee4b249d47a46d25

Fix a bit of UB in __independent_bits_engine. Fixes PR#34663

llvm-svn: 313776

libcxx/include/algorithm

diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 31df79f..282083a 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -3013,6 +3013,7 @@
 _UIntType
 __independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
 {
+    const size_t _WRt = numeric_limits<result_type>::digits;
     result_type _Sp = 0;
     for (size_t __k = 0; __k < __n0_; ++__k)
     {
@@ -3021,7 +3022,7 @@
         {
             __u = __e_() - _Engine::min();
         } while (__u >= __y0_);
-        if (__w0_ < _WDt)
+        if (__w0_ < _WRt)
             _Sp <<= __w0_;
         else
             _Sp = 0;
@@ -3034,7 +3035,7 @@
         {
             __u = __e_() - _Engine::min();
         } while (__u >= __y1_);
-        if (__w0_ < _WDt - 1)
+        if (__w0_ < _WRt - 1)
             _Sp <<= __w0_ + 1;
         else
             _Sp = 0;