From 30fb4afccf883f4b3295735c4502bea6e56de4e4 Mon Sep 17 00:00:00 2001
From: Matt Stephanson <stephanson.matt@gmail.com>
Date: Tue, 23 Sep 2025 22:39:23 -0700
Subject: [PATCH 1/3] Prevent full-width shifts in `independent_bits_engine`

---
 stl/inc/random | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/stl/inc/random b/stl/inc/random
index 7a033d12e4c..93cc44efab2 100644
--- a/stl/inc/random
+++ b/stl/inc/random
@@ -1900,29 +1900,27 @@ public:
     }
 
     _NODISCARD result_type operator()() {
-        size_t _Idx       = 0;
-        result_type _Res  = 0;
         result_type _Mask = ((result_type{1} << (_Wx0 - 1)) << 1) - 1;
         _Eres _Val;
 
+        do { // get a small enough value
+            _Val = _Eng() - (_Engine::min) ();
+        } while (_Val > _Yx0);
+        result_type _Res = static_cast<result_type>(_Val) & _Mask;
+
+        size_t _Idx = 1;
         for (; _Idx < _Nx0; ++_Idx) { // pack _Wx0-bit values
-            for (;;) { // get a small enough value
+            do {
                 _Val = _Eng() - (_Engine::min) ();
-                if (_Val <= _Yx0) {
-                    break;
-                }
-            }
+            } while (_Val > _Yx0);
             _Res = _Res << _Wx0 | (static_cast<result_type>(_Val) & _Mask);
         }
 
         _Mask = _Mask << 1 | 1;
         for (; _Idx < _Nx; ++_Idx) { // pack _Wx0+1-bit values
-            for (;;) { // get a small enough value
+            do {
                 _Val = _Eng() - (_Engine::min) ();
-                if (_Val <= _Yx1) {
-                    break;
-                }
-            }
+            } while (_Val > _Yx1);
             _Res = _Res << (_Wx0 + 1) | (static_cast<result_type>(_Val) & _Mask);
         }
         return _Res;
@@ -1974,8 +1972,13 @@ private:
             _Nx  = (_Wx + _Mx - 1) / _Mx + _Nfix; // trial _Nx
             _Wx0 = _Wx / _Nx;
             _Nx0 = _Nx - _Wx % _Nx;
-            _Yx0 = (_Rx >> _Wx0) << _Wx0;
-            _Yx1 = (((_Rx >> _Wx0) >> 1) << _Wx0) << 1;
+            if (_Wx < sizeof(_Eres) * CHAR_BIT) {
+                _Yx0 = (_Rx >> _Wx0) << _Wx0;
+                _Yx1 = (((_Rx >> _Wx0) >> 1) << _Wx0) << 1;
+            } else {
+                _Yx0 = 0;
+                _Yx1 = 0;
+            }
             if (_Nfix == 1 || _Rx - _Yx0 <= _Yx0 / _Nx) {
                 break; // also works if _Rx == 0 (_Mx == all bits)
             }

From cae489ea5bf385f0e0fa13b228036e813921e659 Mon Sep 17 00:00:00 2001
From: Matt Stephanson <stephanson.matt@gmail.com>
Date: Wed, 24 Sep 2025 19:57:38 -0700
Subject: [PATCH 2/3] Fix typo

---
 stl/inc/random | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stl/inc/random b/stl/inc/random
index 93cc44efab2..dddb30fc2ec 100644
--- a/stl/inc/random
+++ b/stl/inc/random
@@ -1972,7 +1972,7 @@ private:
             _Nx  = (_Wx + _Mx - 1) / _Mx + _Nfix; // trial _Nx
             _Wx0 = _Wx / _Nx;
             _Nx0 = _Nx - _Wx % _Nx;
-            if (_Wx < sizeof(_Eres) * CHAR_BIT) {
+            if (_Wx0 < sizeof(_Eres) * CHAR_BIT) {
                 _Yx0 = (_Rx >> _Wx0) << _Wx0;
                 _Yx1 = (((_Rx >> _Wx0) >> 1) << _Wx0) << 1;
             } else {

From 32bf2ea1fc13130859f545d61bd38a2f0340f04b Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 24 Sep 2025 22:09:36 -0700
Subject: [PATCH 3/3] Add newline.

---
 stl/inc/random | 1 +
 1 file changed, 1 insertion(+)

diff --git a/stl/inc/random b/stl/inc/random
index dddb30fc2ec..f2f83da50b9 100644
--- a/stl/inc/random
+++ b/stl/inc/random
@@ -1979,6 +1979,7 @@ private:
                 _Yx0 = 0;
                 _Yx1 = 0;
             }
+
             if (_Nfix == 1 || _Rx - _Yx0 <= _Yx0 / _Nx) {
                 break; // also works if _Rx == 0 (_Mx == all bits)
             }