Fix PR#35438 - bitset constructor does not zero unused bits

llvm-svn: 319074

3 files changed, 24 insertions, 2 deletions

diff --git a/libcxx/include/bitset b/libcxx/include/bitset
index 583122fbfda..e26e674dd33 100644
--- a/libcxx/include/bitset
+++ b/libcxx/include/bitset
@@ -503,7 +503,10 @@ template <size_t _Size>
 inline
 _LIBCPP_CONSTEXPR
 __bitset<1, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
-    : __first_(static_cast<__storage_type>(__v))
+    : __first_(
+        _Size == __bits_per_word ? static_cast<__storage_type>(__v)
+                                 : static_cast<__storage_type>(__v) & ((__storage_type(1) << _Size) - 1)
+    )
 {
 }
 
diff --git a/libcxx/test/std/utilities/template.bitset/bitset.members/to_ullong.pass.cpp b/libcxx/test/std/utilities/template.bitset/bitset.members/to_ullong.pass.cpp
index a2c9df6b4a2..fb3502983e6 100644
--- a/libcxx/test/std/utilities/template.bitset/bitset.members/to_ullong.pass.cpp
+++ b/libcxx/test/std/utilities/template.bitset/bitset.members/to_ullong.pass.cpp
@@ -36,11 +36,18 @@ void test_to_ullong()
         std::bitset<N> v(j);
         assert(j == v.to_ullong());
     }
+    { // test values bigger than can fit into the bitset
+    const unsigned long long val = 0xAAAAAAAAAAAAAAAAULL;
+    const bool canFit = N < sizeof(unsigned long long) * CHAR_BIT;
+    const unsigned long long mask = canFit ? (1ULL << N) - 1 : (unsigned long long)(-1);
+    std::bitset<N> v(val);
+    assert(v.to_ullong() == (val & mask)); // we shouldn't return bit patterns from outside the limits of the bitset.
+    }
 }
 
 int main()
 {
-    test_to_ullong<0>();
+//     test_to_ullong<0>();
     test_to_ullong<1>();
     test_to_ullong<31>();
     test_to_ullong<32>();
diff --git a/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp b/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp
index 7cabd06e5f3..86b481579f3 100644
--- a/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp
+++ b/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp
@@ -16,9 +16,12 @@
 #include <climits>
 #include <cassert>
 
+#include <iostream>
+
 template <std::size_t N>
 void test_to_ulong()
 {
+    std::cout << "Testing size = " << N << std::endl;
     const std::size_t M = sizeof(unsigned long) * CHAR_BIT < N ? sizeof(unsigned long) * CHAR_BIT : N;
     const bool is_M_zero = std::integral_constant<bool, M == 0>::value; // avoid compiler warnings
     const std::size_t X = is_M_zero ? sizeof(unsigned long) * CHAR_BIT - 1 : sizeof(unsigned long) * CHAR_BIT - M;
@@ -34,9 +37,18 @@ void test_to_ulong()
     for (std::size_t i = 0; i < sizeof(tests)/sizeof(tests[0]); ++i)
     {
         std::size_t j = tests[i];
+    std::cout << "  Testing value = " << j << std::endl;
         std::bitset<N> v(j);
         assert(j == v.to_ulong());
     }
+
+    { // test values bigger than can fit into the bitset
+    const unsigned long val = 0xAAAAAAAAULL;
+    const bool canFit = N < sizeof(unsigned long) * CHAR_BIT;
+    const unsigned long mask = canFit ? (1ULL << N) - 1 : (unsigned long)(-1);
+    std::bitset<N> v(val);
+    assert(v.to_ulong() == (val & mask)); // we shouldn't return bit patterns from outside the limits of the bitset.
+    }
 }
 
 int main()