Fix

Author: H-G-Hristov

libcxx/include/bitset

@@ -791,7 +791,7 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>& bitset<_Size>
 }
 
 template <size_t _Size>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>& bitset<_Size>::set() _NOEXCEPT {
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>& bitset<_Size>::set() _NOEXCEPT {
   std::fill_n(__base::__make_iter(0), _Size, true);
   return *this;
 }
@@ -928,23 +928,23 @@ bitset<_Size>::operator>>(size_t __pos) const _NOEXCEPT {
 }
 
 template <size_t _Size>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
 operator&(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT {
   bitset<_Size> __r = __x;
   __r &= __y;
   return __r;
 }
 
 template <size_t _Size>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
 operator|(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT {
   bitset<_Size> __r = __x;
   __r |= __y;
   return __r;
 }
 
 template <size_t _Size>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX23 bitset<_Size>
 operator^(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT {
   bitset<_Size> __r = __x;
   __r ^= __y;
@@ -953,7 +953,9 @@ operator^(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT {
 
 template <size_t _Size>
 struct hash<bitset<_Size> > : public __unary_function<bitset<_Size>, size_t> {
-  _LIBCPP_HIDE_FROM_ABI size_t operator()(const bitset<_Size>& __bs) const _NOEXCEPT { return __bs.__hash_code(); }
+  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_t operator()(const bitset<_Size>& __bs) const _NOEXCEPT {
+    return __bs.__hash_code();
+  }
 };
 
 template <class _CharT, class _Traits, size_t _Size>

libcxx/test/libcxx/utilities/template.bitset/nodiscard.verify.cpp

@@ -6,8 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03
-
 // <bitset>
 
 // Check that functions are marked [[nodiscard]]
@@ -18,8 +16,8 @@
 #include "test_allocator.h"
 
 void test() {
-  std::bitset<10> bs;
-  const std::bitset<10> cbs;
+  std::bitset<11> bs;
+  const std::bitset<11> cbs;
 
   // std::bitset<>::reference operator~() const noexcept;
   ~bs[0]; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
@@ -34,7 +32,7 @@ void test() {
   struct CharTraits : public std::char_traits<char> {};
 
   // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
-  bs.to_string<char, CharTraits, test_allocator<char>>();
+  bs.to_string<char, CharTraits, test_allocator<char> >();
   // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
   bs.to_string<char, CharTraits>();
 #if !defined(TEST_HAS_NO_WIDE_CHARACTERS)
@@ -52,4 +50,12 @@ void test() {
   bs.none();  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   bs << 1;    // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   bs >> 1;    // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  bs & bs; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  bs | bs; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  bs ^ bs; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  std::hash<std::bitset<11> > hash;
+
+  hash(bs); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 }