libstdc++: Add [[nodiscard]] attribute to <string> and <string_view>

libstdc++-v3/ChangeLog:

	* include/bits/basic_string.h (basic_string): Add nodiscard
	attribute to all relevant functions.
	* include/std/string_view (basic_string_view): Likewise.
	* testsuite/21_strings/basic_string/capacity/1.cc: Cast unused
	results to void.
	* testsuite/21_strings/basic_string/capacity/char/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string/capacity/wchar_t/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string/cons/char/self_move.cc:
	Likewise.
	* testsuite/21_strings/basic_string/element_access/char/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string/element_access/char/21674.cc:
	Likewise.
	* testsuite/21_strings/basic_string/element_access/wchar_t/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string/element_access/wchar_t/21674.cc:
	Likewise.
	* testsuite/21_strings/basic_string/lwg2758.cc: Likewise.
	* testsuite/21_strings/basic_string/lwg2946.cc: Likewise.
	* testsuite/21_strings/basic_string/operations/contains/nonnull.cc:
	Add -Wno-unused-result to options.
	* testsuite/21_strings/basic_string/operations/ends_with/nonnull.cc:
	Likewise.
	* testsuite/21_strings/basic_string/operations/starts_with/nonnull.cc:
	Likewise.
	* testsuite/21_strings/basic_string/operators/char/1.cc: Cast
	unused results to void.
	* testsuite/21_strings/basic_string/operators/wchar_t/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/capacity/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/element_access/char/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/element_access/char/2.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/element_access/wchar_t/1.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/element_access/wchar_t/2.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/operations/contains/nonnull.cc:
	Likewise.
	Add -Wno-unused-result to options.
	* testsuite/21_strings/basic_string_view/operations/ends_with/nonnull.cc:
	Likewise.
	* testsuite/21_strings/basic_string_view/operations/starts_with/nonnull.cc:
	Likewise.
	* testsuite/27_io/basic_stringbuf/sputbackc/char/1.cc: Cast
	unused results to void.
	* testsuite/27_io/basic_stringbuf/sputbackc/wchar_t/1.cc:
	Likewise.
	* testsuite/27_io/basic_stringbuf/sungetc/char/1.cc: Likewise.
	* testsuite/27_io/basic_stringbuf/sungetc/wchar_t/1.cc:
	Likewise.

29 files changed, 279 insertions, 157 deletions

diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 9d8b415..0df64ea 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -942,7 +942,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read/write iterator that points to the first character in
        *  the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       iterator
       begin() _GLIBCXX_NOEXCEPT
       { return iterator(_M_data()); }
@@ -951,7 +951,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read-only (constant) iterator that points to the first
        *  character in the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_iterator
       begin() const _GLIBCXX_NOEXCEPT
       { return const_iterator(_M_data()); }
@@ -960,7 +960,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read/write iterator that points one past the last
        *  character in the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       iterator
       end() _GLIBCXX_NOEXCEPT
       { return iterator(_M_data() + this->size()); }
@@ -969,7 +969,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read-only (constant) iterator that points one past the
        *  last character in the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_iterator
       end() const _GLIBCXX_NOEXCEPT
       { return const_iterator(_M_data() + this->size()); }
@@ -979,7 +979,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  character in the %string.  Iteration is done in reverse element
        *  order.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       reverse_iterator
       rbegin() _GLIBCXX_NOEXCEPT
       { return reverse_iterator(this->end()); }
@@ -989,7 +989,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  to the last character in the %string.  Iteration is done in
        *  reverse element order.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reverse_iterator
       rbegin() const _GLIBCXX_NOEXCEPT
       { return const_reverse_iterator(this->end()); }
@@ -999,7 +999,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  first character in the %string.  Iteration is done in reverse
        *  element order.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       reverse_iterator
       rend() _GLIBCXX_NOEXCEPT
       { return reverse_iterator(this->begin()); }
@@ -1009,7 +1009,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  to one before the first character in the %string.  Iteration
        *  is done in reverse element order.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reverse_iterator
       rend() const _GLIBCXX_NOEXCEPT
       { return const_reverse_iterator(this->begin()); }
@@ -1019,7 +1019,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read-only (constant) iterator that points to the first
        *  character in the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_iterator
       cbegin() const noexcept
       { return const_iterator(this->_M_data()); }
@@ -1028,7 +1028,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read-only (constant) iterator that points one past the
        *  last character in the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_iterator
       cend() const noexcept
       { return const_iterator(this->_M_data() + this->size()); }
@@ -1038,7 +1038,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  to the last character in the %string.  Iteration is done in
        *  reverse element order.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reverse_iterator
       crbegin() const noexcept
       { return const_reverse_iterator(this->end()); }
@@ -1048,7 +1048,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  to one before the first character in the %string.  Iteration
        *  is done in reverse element order.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reverse_iterator
       crend() const noexcept
       { return const_reverse_iterator(this->begin()); }
@@ -1058,20 +1058,20 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       // Capacity:
       ///  Returns the number of characters in the string, not including any
       ///  null-termination.
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       size() const _GLIBCXX_NOEXCEPT
       { return _M_string_length; }
 
       ///  Returns the number of characters in the string, not including any
       ///  null-termination.
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       length() const _GLIBCXX_NOEXCEPT
       { return _M_string_length; }
 
       ///  Returns the size() of the largest possible %string.
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       max_size() const _GLIBCXX_NOEXCEPT
       { return (_Alloc_traits::max_size(_M_get_allocator()) - 1) / 2; }
@@ -1127,7 +1127,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns the total number of characters that the %string can hold
        *  before needing to allocate more memory.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       capacity() const _GLIBCXX_NOEXCEPT
       {
@@ -1194,7 +1194,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  out_of_range lookups are not defined. (For checked lookups
        *  see at().)
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reference
       operator[] (size_type __pos) const _GLIBCXX_NOEXCEPT
       {
@@ -1212,7 +1212,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  out_of_range lookups are not defined. (For checked lookups
        *  see at().)
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       reference
       operator[](size_type __pos)
       {
@@ -1234,7 +1234,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  first checked that it is in the range of the string.  The function
        *  throws out_of_range if the check fails.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reference
       at(size_type __n) const
       {
@@ -1256,7 +1256,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  first checked that it is in the range of the string.  The function
        *  throws out_of_range if the check fails.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       reference
       at(size_type __n)
       {
@@ -1273,7 +1273,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read/write reference to the data at the first
        *  element of the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       reference
       front() noexcept
       {
@@ -1285,7 +1285,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read-only (constant) reference to the data at the first
        *  element of the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reference
       front() const noexcept
       {
@@ -1297,7 +1297,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read/write reference to the data at the last
        *  element of the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       reference
       back() noexcept
       {
@@ -1309,7 +1309,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns a read-only (constant) reference to the data at the
        *  last element of the %string.
        */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const_reference
       back() const noexcept
       {
@@ -2549,7 +2549,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  This is a handle to internal data.  Do not modify or dire things may
        *  happen.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const _CharT*
       c_str() const _GLIBCXX_NOEXCEPT
       { return _M_data(); }
@@ -2562,7 +2562,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  allows modifying the contents use @c &str[0] instead,
        *  (or in C++17 the non-const @c str.data() overload).
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       const _CharT*
       data() const _GLIBCXX_NOEXCEPT
       { return _M_data(); }
@@ -2574,7 +2574,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  This is a pointer to the character sequence held by the string.
        *  Modifying the characters in the sequence is allowed.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       _CharT*
       data() noexcept
       { return _M_data(); }
@@ -2583,7 +2583,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       /**
        *  @brief  Return copy of allocator used to construct this string.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       allocator_type
       get_allocator() const _GLIBCXX_NOEXCEPT
       { return _M_get_allocator(); }
@@ -2600,7 +2600,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  returns the index where it begins.  If not found, returns
        *  npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find(const _CharT* __s, size_type __pos, size_type __n) const
       _GLIBCXX_NOEXCEPT;
@@ -2615,7 +2615,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  this string.  If found, returns the index where it begins.  If not
        *  found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find(const basic_string& __str, size_type __pos = 0) const
       _GLIBCXX_NOEXCEPT
@@ -2629,7 +2629,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Index of start of first occurrence.
       */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, size_type>
 	find(const _Tp& __svt, size_type __pos = 0) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -2649,7 +2649,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  __s within this string.  If found, returns the index where
        *  it begins.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find(const _CharT* __s, size_type __pos = 0) const _GLIBCXX_NOEXCEPT
       {
@@ -2667,7 +2667,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  this string.  If found, returns the index where it was
        *  found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find(_CharT __c, size_type __pos = 0) const _GLIBCXX_NOEXCEPT;
 
@@ -2681,7 +2681,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  __str within this string.  If found, returns the index where
        *  it begins.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       rfind(const basic_string& __str, size_type __pos = npos) const
       _GLIBCXX_NOEXCEPT
@@ -2695,7 +2695,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Index of start of last occurrence.
       */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, size_type>
 	rfind(const _Tp& __svt, size_type __pos = npos) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -2717,7 +2717,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  returns the index where it begins.  If not found, returns
        *  npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       rfind(const _CharT* __s, size_type __pos, size_type __n) const
       _GLIBCXX_NOEXCEPT;
@@ -2732,7 +2732,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @a __s within this string.  If found, returns the index
        *  where it begins.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       rfind(const _CharT* __s, size_type __pos = npos) const
       {
@@ -2750,7 +2750,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  this string.  If found, returns the index where it was
        *  found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       rfind(_CharT __c, size_type __pos = npos) const _GLIBCXX_NOEXCEPT;
 
@@ -2765,7 +2765,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  returns the index where it was found.  If not found, returns
        *  npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_of(const basic_string& __str, size_type __pos = 0) const
       _GLIBCXX_NOEXCEPT
@@ -2780,7 +2780,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Index of first occurrence.
       */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, size_type>
 	find_first_of(const _Tp& __svt, size_type __pos = 0) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -2802,7 +2802,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  found, returns the index where it was found.  If not found,
        *  returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
       _GLIBCXX_NOEXCEPT;
@@ -2817,7 +2817,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  characters of @a __s within this string.  If found, returns
        *  the index where it was found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_of(const _CharT* __s, size_type __pos = 0) const
       _GLIBCXX_NOEXCEPT
@@ -2838,7 +2838,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *
        *  Note: equivalent to find(__c, __pos).
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_of(_CharT __c, size_type __pos = 0) const _GLIBCXX_NOEXCEPT
       { return this->find(__c, __pos); }
@@ -2854,7 +2854,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  returns the index where it was found.  If not found, returns
        *  npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_of(const basic_string& __str, size_type __pos = npos) const
       _GLIBCXX_NOEXCEPT
@@ -2869,7 +2869,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Index of last occurrence.
       */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, size_type>
 	find_last_of(const _Tp& __svt, size_type __pos = npos) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -2891,7 +2891,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  found, returns the index where it was found.  If not found,
        *  returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
       _GLIBCXX_NOEXCEPT;
@@ -2906,7 +2906,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  characters of @a __s within this string.  If found, returns
        *  the index where it was found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_of(const _CharT* __s, size_type __pos = npos) const
       _GLIBCXX_NOEXCEPT
@@ -2927,7 +2927,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *
        *  Note: equivalent to rfind(__c, __pos).
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_of(_CharT __c, size_type __pos = npos) const _GLIBCXX_NOEXCEPT
       { return this->rfind(__c, __pos); }
@@ -2942,7 +2942,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  in @a __str within this string.  If found, returns the index where it
        *  was found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_not_of(const basic_string& __str, size_type __pos = 0) const
       _GLIBCXX_NOEXCEPT
@@ -2957,8 +2957,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Index of first occurrence.
        */
       template<typename _Tp>
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, size_type>
-	_GLIBCXX20_CONSTEXPR
 	find_first_not_of(const _Tp& __svt, size_type __pos = 0) const
 	noexcept(is_same<_Tp, __sv_type>::value)
 	{
@@ -2979,7 +2979,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  this string.  If found, returns the index where it was
        *  found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_not_of(const _CharT* __s, size_type __pos,
 			size_type __n) const _GLIBCXX_NOEXCEPT;
@@ -2994,7 +2994,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  contained in @a __s within this string.  If found, returns
        *  the index where it was found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_not_of(const _CharT* __s, size_type __pos = 0) const
       _GLIBCXX_NOEXCEPT
@@ -3013,7 +3013,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  other than @a __c within this string.  If found, returns the
        *  index where it was found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_first_not_of(_CharT __c, size_type __pos = 0) const
       _GLIBCXX_NOEXCEPT;
@@ -3029,7 +3029,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  returns the index where it was found.  If not found, returns
        *  npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_not_of(const basic_string& __str, size_type __pos = npos) const
       _GLIBCXX_NOEXCEPT
@@ -3044,7 +3044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Index of last occurrence.
        */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, size_type>
 	find_last_not_of(const _Tp& __svt, size_type __pos = npos) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -3066,7 +3066,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  If found, returns the index where it was found.  If not found,
        *  returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_not_of(const _CharT* __s, size_type __pos,
 		       size_type __n) const _GLIBCXX_NOEXCEPT;
@@ -3081,7 +3081,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  returns the index where it was found.  If not found, returns
        *  npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_not_of(const _CharT* __s, size_type __pos = npos) const
       _GLIBCXX_NOEXCEPT
@@ -3100,7 +3100,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @a __c within this string.  If found, returns the index where it was
        *  found.  If not found, returns npos.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       find_last_not_of(_CharT __c, size_type __pos = npos) const
       _GLIBCXX_NOEXCEPT;
@@ -3117,7 +3117,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  short, use the remainder of the characters.  If @a __pos is
        *  beyond the end of the string, out_of_range is thrown.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       basic_string
       substr(size_type __pos = 0, size_type __n = npos) const
       { return basic_string(*this,
@@ -3137,7 +3137,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  If the result of the comparison is nonzero returns it,
        *  otherwise the shorter one is ordered first.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       int
       compare(const basic_string& __str) const
       {
@@ -3158,7 +3158,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Integer < 0, 0, or > 0.
        */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, int>
 	compare(const _Tp& __svt) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -3183,7 +3183,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Integer < 0, 0, or > 0.
        */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, int>
 	compare(size_type __pos, size_type __n, const _Tp& __svt) const
 	noexcept(is_same<_Tp, __sv_type>::value)
@@ -3203,7 +3203,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  @return  Integer < 0, 0, or > 0.
        */
       template<typename _Tp>
-	_GLIBCXX20_CONSTEXPR
+	_GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
 	_If_sv<_Tp, int>
 	compare(size_type __pos1, size_type __n1, const _Tp& __svt,
 		size_type __pos2, size_type __n2 = npos) const
@@ -3234,7 +3234,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  result of the comparison is nonzero returns it, otherwise
        *  the shorter one is ordered first.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       int
       compare(size_type __pos, size_type __n, const basic_string& __str) const
       {
@@ -3271,7 +3271,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  If the result of the comparison is nonzero returns it,
        *  otherwise the shorter one is ordered first.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       int
       compare(size_type __pos1, size_type __n1, const basic_string& __str,
 	      size_type __pos2, size_type __n2 = npos) const
@@ -3302,7 +3302,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  comparison is nonzero returns it, otherwise the shorter one is
        *  ordered first.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       int
       compare(const _CharT* __s) const _GLIBCXX_NOEXCEPT
       {
@@ -3337,7 +3337,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  the comparison is nonzero returns it, otherwise the shorter
        *  one is ordered first.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       int
       compare(size_type __pos, size_type __n1, const _CharT* __s) const
       {
@@ -3376,7 +3376,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  NB: s must have at least n2 characters, &apos;\\0&apos; has
        *  no special meaning.
       */
-      _GLIBCXX20_CONSTEXPR
+      _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       int
       compare(size_type __pos, size_type __n1, const _CharT* __s,
 	      size_type __n2) const
@@ -3392,43 +3392,49 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       }
 
 #if __cplusplus >= 202002L
+      [[nodiscard]]
       constexpr bool
       starts_with(basic_string_view<_CharT, _Traits> __x) const noexcept
       { return __sv_type(this->data(), this->size()).starts_with(__x); }
 
+      [[nodiscard]]
       constexpr bool
       starts_with(_CharT __x) const noexcept
       { return __sv_type(this->data(), this->size()).starts_with(__x); }
 
-      [[__gnu__::__nonnull__]]
+      [[nodiscard, __gnu__::__nonnull__]]
       constexpr bool
       starts_with(const _CharT* __x) const noexcept
       { return __sv_type(this->data(), this->size()).starts_with(__x); }
 
+      [[nodiscard]]
       constexpr bool
       ends_with(basic_string_view<_CharT, _Traits> __x) const noexcept
       { return __sv_type(this->data(), this->size()).ends_with(__x); }
 
+      [[nodiscard]]
       constexpr bool
       ends_with(_CharT __x) const noexcept
       { return __sv_type(this->data(), this->size()).ends_with(__x); }
 
-      [[__gnu__::__nonnull__]]
+      [[nodiscard, __gnu__::__nonnull__]]
       constexpr bool
       ends_with(const _CharT* __x) const noexcept
       { return __sv_type(this->data(), this->size()).ends_with(__x); }
 #endif // C++20
 
 #if __cplusplus > 202002L
+      [[nodiscard]]
       constexpr bool
       contains(basic_string_view<_CharT, _Traits> __x) const noexcept
       { return __sv_type(this->data(), this->size()).contains(__x); }
 
+      [[nodiscard]]
       constexpr bool
       contains(_CharT __x) const noexcept
       { return __sv_type(this->data(), this->size()).contains(__x); }
 
-      [[__gnu__::__nonnull__]]
+      [[nodiscard, __gnu__::__nonnull__]]
       constexpr bool
       contains(const _CharT* __x) const noexcept
       { return __sv_type(this->data(), this->size()).contains(__x); }
@@ -3483,7 +3489,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  New string with value of @a __lhs followed by @a __rhs.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     basic_string<_CharT, _Traits, _Alloc>
     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3500,7 +3506,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  New string with value of @a __lhs followed by @a __rhs.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     basic_string<_CharT,_Traits,_Alloc>
     operator+(const _CharT* __lhs,
 	      const basic_string<_CharT,_Traits,_Alloc>& __rhs);
@@ -3512,7 +3518,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  New string with @a __lhs followed by @a __rhs.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     basic_string<_CharT,_Traits,_Alloc>
     operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Alloc>& __rhs);
 
@@ -3523,7 +3529,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  New string with @a __lhs followed by @a __rhs.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	      const _CharT* __rhs)
@@ -3540,7 +3546,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  New string with @a __lhs followed by @a __rhs.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, _CharT __rhs)
     {
@@ -3553,7 +3559,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
 
 #if __cplusplus >= 201103L
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3567,7 +3573,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
     { return std::move(__rhs.insert(0, __lhs)); }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
 	      basic_string<_CharT, _Traits, _Alloc>&& __rhs)
@@ -3590,28 +3596,28 @@ _GLIBCXX_END_NAMESPACE_CXX11
     }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(const _CharT* __lhs,
 	      basic_string<_CharT, _Traits, _Alloc>&& __rhs)
     { return std::move(__rhs.insert(0, __lhs)); }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(_CharT __lhs,
 	      basic_string<_CharT, _Traits, _Alloc>&& __rhs)
     { return std::move(__rhs.insert(0, 1, __lhs)); }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
 	      const _CharT* __rhs)
     { return std::move(__lhs.append(__rhs)); }
 
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline basic_string<_CharT, _Traits, _Alloc>
     operator+(basic_string<_CharT, _Traits, _Alloc>&& __lhs,
 	      _CharT __rhs)
@@ -3626,7 +3632,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs.compare(@a __rhs) == 0.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline bool
     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3643,7 +3649,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs.compare(@a __rhs) == 0.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
-    _GLIBCXX20_CONSTEXPR
+    _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
     inline bool
     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const _CharT* __rhs)
@@ -3661,6 +3667,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *	       greater than, or incomparable with `__rhs`.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    [[nodiscard]]
     constexpr auto
     operator<=>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 		const basic_string<_CharT, _Traits, _Alloc>& __rhs) noexcept
@@ -3675,6 +3682,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *	       greater than, or incomparable with `__rhs`.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    [[nodiscard]]
     constexpr auto
     operator<=>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 		const _CharT* __rhs) noexcept
@@ -3688,6 +3696,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __rhs.compare(@a __lhs) == 0.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator==(const _CharT* __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3701,6 +3710,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs.compare(@a __rhs) != 0.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3714,6 +3724,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __rhs.compare(@a __lhs) != 0.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator!=(const _CharT* __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3726,6 +3737,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs.compare(@a __rhs) != 0.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator!=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const _CharT* __rhs)
@@ -3739,6 +3751,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs precedes @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3752,6 +3765,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs precedes @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	      const _CharT* __rhs)
@@ -3764,6 +3778,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs precedes @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator<(const _CharT* __lhs,
 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3777,6 +3792,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs follows @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3790,6 +3806,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs follows @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	      const _CharT* __rhs)
@@ -3802,6 +3819,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs follows @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator>(const _CharT* __lhs,
 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3815,6 +3833,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs doesn't follow @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3828,6 +3847,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs doesn't follow @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const _CharT* __rhs)
@@ -3840,6 +3860,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs doesn't follow @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator<=(const _CharT* __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3853,6 +3874,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs doesn't precede @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator>=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -3866,6 +3888,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs doesn't precede @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator>=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
 	       const _CharT* __rhs)
@@ -3878,6 +3901,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
    *  @return  True if @a __lhs doesn't precede @a __rhs.  False otherwise.
    */
   template<typename _CharT, typename _Traits, typename _Alloc>
+    _GLIBCXX_NODISCARD
     inline bool
     operator>=(const _CharT* __lhs,
 	     const basic_string<_CharT, _Traits, _Alloc>& __rhs)
@@ -4060,6 +4084,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
   // DR 1261. Insufficent overloads for to_string / to_wstring
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(int __val)
 #if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32
@@ -4074,6 +4099,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     return __str;
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(unsigned __val)
 #if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32
@@ -4085,6 +4111,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     return __str;
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(long __val)
 #if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32
@@ -4099,6 +4126,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     return __str;
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(unsigned long __val)
 #if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32
@@ -4110,6 +4138,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     return __str;
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(long long __val)
   {
@@ -4122,6 +4151,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
     return __str;
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(unsigned long long __val)
   {
@@ -4133,6 +4163,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 #if _GLIBCXX_USE_C99_STDIO
   // NB: (v)snprintf vs sprintf.
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(float __val)
   {
@@ -4142,6 +4173,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 					   "%f", __val);
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(double __val)
   {
@@ -4151,6 +4183,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 					   "%f", __val);
   }
 
+  _GLIBCXX_NODISCARD
   inline string
   to_string(long double __val)
   {
@@ -4202,40 +4235,47 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
 #ifndef _GLIBCXX_HAVE_BROKEN_VSWPRINTF
   // DR 1261.
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(int __val)
   { return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, 4 * sizeof(int),
 					    L"%d", __val); }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(unsigned __val)
   { return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
 					    4 * sizeof(unsigned),
 					    L"%u", __val); }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(long __val)
   { return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf, 4 * sizeof(long),
 					    L"%ld", __val); }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(unsigned long __val)
   { return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
 					    4 * sizeof(unsigned long),
 					    L"%lu", __val); }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(long long __val)
   { return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
 					    4 * sizeof(long long),
 					    L"%lld", __val); }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(unsigned long long __val)
   { return __gnu_cxx::__to_xstring<wstring>(&std::vswprintf,
 					    4 * sizeof(unsigned long long),
 					    L"%llu", __val); }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(float __val)
   {
@@ -4245,6 +4285,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 					    L"%f", __val);
   }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(double __val)
   {
@@ -4254,6 +4295,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 					    L"%f", __val);
   }
 
+  _GLIBCXX_NODISCARD
   inline wstring
   to_wstring(long double __val)
   {
@@ -4287,6 +4329,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __str_hash_base
     : public __hash_base<size_t, _StrT>
     {
+      [[__nodiscard__]]
       size_t
       operator()(const _StrT& __s) const noexcept
       { return _Hash_impl::hash(__s.data(), __s.length() * sizeof(_CharT)); }
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index 5b96ffe..2604af2 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -129,7 +129,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       constexpr basic_string_view(const basic_string_view&) noexcept = default;
 
-      __attribute__((__nonnull__)) constexpr
+      [[__gnu__::__nonnull__]]
+      constexpr
       basic_string_view(const _CharT* __str) noexcept
       : _M_len{traits_type::length(__str)},
 	_M_str{__str}
@@ -172,54 +173,64 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif // C++23
 #endif // C++20
 
-
       constexpr basic_string_view&
       operator=(const basic_string_view&) noexcept = default;
 
       // [string.view.iterators], iterator support
 
+      [[nodiscard]]
       constexpr const_iterator
       begin() const noexcept
       { return this->_M_str; }
 
+      [[nodiscard]]
       constexpr const_iterator
       end() const noexcept
       { return this->_M_str + this->_M_len; }
 
+      [[nodiscard]]
       constexpr const_iterator
       cbegin() const noexcept
       { return this->_M_str; }
 
+      [[nodiscard]]
       constexpr const_iterator
       cend() const noexcept
       { return this->_M_str + this->_M_len; }
 
+      [[nodiscard]]
       constexpr const_reverse_iterator
       rbegin() const noexcept
       { return const_reverse_iterator(this->end()); }
 
+      [[nodiscard]]
       constexpr const_reverse_iterator
       rend() const noexcept
       { return const_reverse_iterator(this->begin()); }
 
+      [[nodiscard]]
       constexpr const_reverse_iterator
       crbegin() const noexcept
       { return const_reverse_iterator(this->end()); }
 
+      [[nodiscard]]
       constexpr const_reverse_iterator
       crend() const noexcept
       { return const_reverse_iterator(this->begin()); }
 
       // [string.view.capacity], capacity
 
+      [[nodiscard]]
       constexpr size_type
       size() const noexcept
       { return this->_M_len; }
 
+      [[nodiscard]]
       constexpr size_type
       length() const noexcept
       { return _M_len; }
 
+      [[nodiscard]]
       constexpr size_type
       max_size() const noexcept
       {
@@ -227,12 +238,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		/ sizeof(value_type) / 4;
       }
 
-      [[nodiscard]] constexpr bool
+      [[nodiscard]]
+      constexpr bool
       empty() const noexcept
       { return this->_M_len == 0; }
 
       // [string.view.access], element access
 
+      [[nodiscard]]
       constexpr const_reference
       operator[](size_type __pos) const noexcept
       {
@@ -240,6 +253,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return *(this->_M_str + __pos);
       }
 
+      [[nodiscard]]
       constexpr const_reference
       at(size_type __pos) const
       {
@@ -250,6 +264,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return *(this->_M_str + __pos);
       }
 
+      [[nodiscard]]
       constexpr const_reference
       front() const noexcept
       {
@@ -257,6 +272,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return *this->_M_str;
       }
 
+      [[nodiscard]]
       constexpr const_reference
       back() const noexcept
       {
@@ -264,6 +280,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return *(this->_M_str + this->_M_len - 1);
       }
 
+      [[nodiscard]]
       constexpr const_pointer
       data() const noexcept
       { return this->_M_str; }
@@ -305,6 +322,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return __rlen;
       }
 
+      [[nodiscard]]
       constexpr basic_string_view
       substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
       {
@@ -313,6 +331,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return basic_string_view{_M_str + __pos, __rlen};
       }
 
+      [[nodiscard]]
       constexpr int
       compare(basic_string_view __str) const noexcept
       {
@@ -323,10 +342,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return __ret;
       }
 
+      [[nodiscard]]
       constexpr int
       compare(size_type __pos1, size_type __n1, basic_string_view __str) const
       { return this->substr(__pos1, __n1).compare(__str); }
 
+      [[nodiscard]]
       constexpr int
       compare(size_type __pos1, size_type __n1,
 	      basic_string_view __str, size_type __pos2, size_type __n2) const
@@ -334,14 +355,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
       }
 
-      __attribute__((__nonnull__)) constexpr int
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr int
       compare(const _CharT* __str) const noexcept
       { return this->compare(basic_string_view{__str}); }
 
-      __attribute__((__nonnull__)) constexpr int
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr int
       compare(size_type __pos1, size_type __n1, const _CharT* __str) const
       { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
 
+      [[nodiscard]]
       constexpr int
       compare(size_type __pos1, size_type __n1,
 	      const _CharT* __str, size_type __n2) const noexcept(false)
@@ -352,19 +376,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #if __cplusplus > 201703L
 #define __cpp_lib_starts_ends_with 201711L
+      [[nodiscard]]
       constexpr bool
       starts_with(basic_string_view __x) const noexcept
       { return this->substr(0, __x.size()) == __x; }
 
+      [[nodiscard]]
       constexpr bool
       starts_with(_CharT __x) const noexcept
       { return !this->empty() && traits_type::eq(this->front(), __x); }
 
-      [[__gnu__::__nonnull__]]
+      [[nodiscard, __gnu__::__nonnull__]]
       constexpr bool
       starts_with(const _CharT* __x) const noexcept
       { return this->starts_with(basic_string_view(__x)); }
 
+      [[nodiscard]]
       constexpr bool
       ends_with(basic_string_view __x) const noexcept
       {
@@ -374,11 +401,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
       }
 
+      [[nodiscard]]
       constexpr bool
       ends_with(_CharT __x) const noexcept
       { return !this->empty() && traits_type::eq(this->back(), __x); }
 
-      [[__gnu__::__nonnull__]]
+      [[nodiscard, __gnu__::__nonnull__]]
       constexpr bool
       ends_with(const _CharT* __x) const noexcept
       { return this->ends_with(basic_string_view(__x)); }
@@ -386,15 +414,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #if __cplusplus > 202002L
 #define __cpp_lib_string_contains 202011L
+      [[nodiscard]]
       constexpr bool
       contains(basic_string_view __x) const noexcept
       { return this->find(__x) != npos; }
 
+      [[nodiscard]]
       constexpr bool
       contains(_CharT __x) const noexcept
       { return this->find(__x) != npos; }
 
-      [[__gnu__::__nonnull__]]
+      [[nodiscard, __gnu__::__nonnull__]]
       constexpr bool
       contains(const _CharT* __x) const noexcept
       { return this->find(__x) != npos; }
@@ -402,99 +432,123 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       // [string.view.find], searching
 
+      [[nodiscard]]
       constexpr size_type
       find(basic_string_view __str, size_type __pos = 0) const noexcept
       { return this->find(__str._M_str, __pos, __str._M_len); }
 
+      [[nodiscard]]
       constexpr size_type
       find(_CharT __c, size_type __pos = 0) const noexcept;
 
+      [[nodiscard]]
       constexpr size_type
       find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 
-      __attribute__((__nonnull__)) constexpr size_type
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr size_type
       find(const _CharT* __str, size_type __pos = 0) const noexcept
       { return this->find(__str, __pos, traits_type::length(__str)); }
 
+      [[nodiscard]]
       constexpr size_type
       rfind(basic_string_view __str, size_type __pos = npos) const noexcept
       { return this->rfind(__str._M_str, __pos, __str._M_len); }
 
+      [[nodiscard]]
       constexpr size_type
       rfind(_CharT __c, size_type __pos = npos) const noexcept;
 
+      [[nodiscard]]
       constexpr size_type
       rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
 
-      __attribute__((__nonnull__)) constexpr size_type
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr size_type
       rfind(const _CharT* __str, size_type __pos = npos) const noexcept
       { return this->rfind(__str, __pos, traits_type::length(__str)); }
 
+      [[nodiscard]]
       constexpr size_type
       find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
       { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
 
+      [[nodiscard]]
       constexpr size_type
       find_first_of(_CharT __c, size_type __pos = 0) const noexcept
       { return this->find(__c, __pos); }
 
+      [[nodiscard]]
       constexpr size_type
       find_first_of(const _CharT* __str, size_type __pos,
 		    size_type __n) const noexcept;
 
-      __attribute__((__nonnull__)) constexpr size_type
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr size_type
       find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
       { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
 
+      [[nodiscard]]
       constexpr size_type
       find_last_of(basic_string_view __str,
 		   size_type __pos = npos) const noexcept
       { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
 
+      [[nodiscard]]
       constexpr size_type
       find_last_of(_CharT __c, size_type __pos=npos) const noexcept
       { return this->rfind(__c, __pos); }
 
+      [[nodiscard]]
       constexpr size_type
       find_last_of(const _CharT* __str, size_type __pos,
 		   size_type __n) const noexcept;
 
-      __attribute__((__nonnull__)) constexpr size_type
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr size_type
       find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
       { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
 
+      [[nodiscard]]
       constexpr size_type
       find_first_not_of(basic_string_view __str,
 			size_type __pos = 0) const noexcept
       { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
 
+      [[nodiscard]]
       constexpr size_type
       find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
 
+      [[nodiscard]]
       constexpr size_type
       find_first_not_of(const _CharT* __str,
 			size_type __pos, size_type __n) const noexcept;
 
-      __attribute__((__nonnull__)) constexpr size_type
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr size_type
       find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
       {
 	return this->find_first_not_of(__str, __pos,
 				       traits_type::length(__str));
       }
 
+      [[nodiscard]]
       constexpr size_type
       find_last_not_of(basic_string_view __str,
 		       size_type __pos = npos) const noexcept
       { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
 
+      [[nodiscard]]
       constexpr size_type
       find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
 
+      [[nodiscard]]
       constexpr size_type
       find_last_not_of(const _CharT* __str,
 		       size_type __pos, size_type __n) const noexcept;
 
-      __attribute__((__nonnull__)) constexpr size_type
+      [[nodiscard, __gnu__::__nonnull__]]
+      constexpr size_type
       find_last_not_of(const _CharT* __str,
 		       size_type __pos = npos) const noexcept
       {
@@ -539,12 +593,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // type (see N3766).
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator==(basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator==(basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -553,6 +609,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #if __cpp_lib_three_way_comparison
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr auto
     operator<=>(basic_string_view<_CharT, _Traits> __x,
 		basic_string_view<_CharT, _Traits> __y) noexcept
@@ -560,6 +617,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr auto
     operator<=>(basic_string_view<_CharT, _Traits> __x,
 		__type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -568,18 +626,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
 #else
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator!=(basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return !(__x == __y); }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator!=(basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -587,18 +648,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return !(__x == __y); }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return !(__x == __y); }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator< (basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) < 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator< (basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -606,18 +670,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __x.compare(__y) < 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) < 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator> (basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) > 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator> (basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -625,18 +692,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __x.compare(__y) > 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) > 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator<=(basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) <= 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator<=(basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -644,18 +714,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __x.compare(__y) <= 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) <= 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator>=(basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
     { return __x.compare(__y) >= 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator>=(basic_string_view<_CharT, _Traits> __x,
                __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
@@ -663,6 +736,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { return __x.compare(__y) >= 0; }
 
   template<typename _CharT, typename _Traits>
+    [[nodiscard]]
     constexpr bool
     operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
@@ -696,6 +770,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct hash<string_view>
     : public __hash_base<size_t, string_view>
     {
+      [[nodiscard]]
       size_t
       operator()(const string_view& __str) const noexcept
       { return std::_Hash_impl::hash(__str.data(), __str.length()); }
@@ -709,6 +784,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct hash<wstring_view>
     : public __hash_base<size_t, wstring_view>
     {
+      [[nodiscard]]
       size_t
       operator()(const wstring_view& __s) const noexcept
       { return std::_Hash_impl::hash(__s.data(),
@@ -724,6 +800,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct hash<u8string_view>
     : public __hash_base<size_t, u8string_view>
     {
+      [[nodiscard]]
       size_t
       operator()(const u8string_view& __str) const noexcept
       { return std::_Hash_impl::hash(__str.data(), __str.length()); }
@@ -738,6 +815,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct hash<u16string_view>
     : public __hash_base<size_t, u16string_view>
     {
+      [[nodiscard]]
       size_t
       operator()(const u16string_view& __s) const noexcept
       { return std::_Hash_impl::hash(__s.data(),
@@ -752,6 +830,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct hash<u32string_view>
     : public __hash_base<size_t, u32string_view>
     {
+      [[nodiscard]]
       size_t
       operator()(const u32string_view& __s) const noexcept
       { return std::_Hash_impl::hash(__s.data(),
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc
index 45af457..1ae4d3d 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/1.cc
@@ -175,7 +175,7 @@ void test01()
   sz03 = str02.size();
   sz04 = str02.length();
   VERIFY( sz03 == sz04 );
-  str02.c_str();
+  (void) str02.c_str();
   sz03 = str02.size();
   sz04 = str02.length();
   VERIFY( sz03 == sz04 );
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc
index 244a795..1da273b 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/char/1.cc
@@ -74,15 +74,15 @@ void test01()
   sz01 = str01.size();
   sz02 = str01.length();
   VERIFY( sz01 == sz02 );
-  str01.c_str();
+  (void) str01.c_str();
   sz01 = str01.size();
   sz02 = str01.length();
   VERIFY( sz01 == sz02 );
 
   sz01 = str01.length();
-  str01.c_str();
+  (void) str01.c_str();
   str011 = str01 +  "_addendum_";
-  str01.c_str();
+  (void) str01.c_str();
   sz02 = str01.length();    
   VERIFY( sz01 == sz02 );
   sz02 = str011.length();
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc
index 5cb682e..6f03e34 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/capacity/wchar_t/1.cc
@@ -71,15 +71,15 @@ void test01()
   sz01 = str01.size();
   sz02 = str01.length();
   VERIFY( sz01 == sz02 );
-  str01.c_str();
+  (void) str01.c_str();
   sz01 = str01.size();
   sz02 = str01.length();
   VERIFY( sz01 == sz02 );
 
   sz01 = str01.length();
-  str01.c_str();
+  (void) str01.c_str();
   str011 = str01 +  L"_addendum_";
-  str01.c_str();
+  (void) str01.c_str();
   sz02 = str01.length();    
   VERIFY( sz01 == sz02 );
   sz02 = str011.length();
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/self_move.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/self_move.cc
index d37fe39..ddd9aea 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/self_move.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/self_move.cc
@@ -32,7 +32,7 @@ test(const char* s)
   String s3 __attribute__((unused)) = s1;
   s1 = std::move(s1);
 
-  s1.begin(); // causes COW string to "leak"
+  (void) s1.begin(); // causes COW string to "leak"
   s1 = std::move(s1);
 
   String s4 __attribute__((unused)) = s1;
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/1.cc
index 7fb4323..5a176c0 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/1.cc
@@ -53,7 +53,7 @@ void test01(void)
   cref cref3 = str01.at(csz01 - 1);
   VERIFY( cref3 == 'a' );
   try {
-    str01.at(csz01);
+    (void) str01.at(csz01);
     VERIFY( false ); // Should not get here, as exception thrown.
   }
   catch(std::out_of_range& fail) {
@@ -68,7 +68,7 @@ void test01(void)
   ref ref3 = str02.at(csz02 - 1);
   VERIFY( ref3 == 'a' );
   try {
-    str02.at(csz02);
+    (void) str02.at(csz02);
     VERIFY( false ); // Should not get here, as exception thrown.
   }
   catch(std::out_of_range& fail) {
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/21674.cc b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/21674.cc
index a5a129b..3ff8d51 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/21674.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/char/21674.cc
@@ -27,5 +27,5 @@ int main()
 {
   typedef std::string string_type;
   string_type s;
-  s[1]; // abort
+  (void) s[1]; // abort
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/1.cc
index 9bb5dcb..f9a07ab 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/1.cc
@@ -53,7 +53,7 @@ void test01(void)
   cref cref3 = str01.at(csz01 - 1);
   VERIFY( cref3 == L'a' );
   try {
-    str01.at(csz01);
+    (void) str01.at(csz01);
     VERIFY( false ); // Should not get here, as exception thrown.
   }
   catch(std::out_of_range& fail) {
@@ -68,7 +68,7 @@ void test01(void)
   ref ref3 = str02.at(csz02 - 1);
   VERIFY( ref3 == L'a' );
   try {
-    str02.at(csz02);
+    (void) str02.at(csz02);
     VERIFY( false ); // Should not get here, as exception thrown.
   }
   catch(std::out_of_range& fail) {
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/21674.cc b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/21674.cc
index 974e6b2..fc023a8 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/21674.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/element_access/wchar_t/21674.cc
@@ -27,5 +27,5 @@ int main()
 {
   typedef std::wstring string_type;
   string_type s;
-  s[1]; // abort
+  (void) s[1]; // abort
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/lwg2758.cc b/libstdc++-v3/testsuite/21_strings/basic_string/lwg2758.cc
index 45d514b..a9dcd9a 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/lwg2758.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/lwg2758.cc
@@ -40,6 +40,6 @@ int main()
     x.replace(0, 3, "foo", 0, 3);
     x.replace(0, 3, cs, 0, 3);
     x = "bar";
-    x.compare(0, 3, "foo", 0, 3);
-    x.compare(0, 3, cs, 0, 3);
+    (void) x.compare(0, 3, "foo", 0, 3);
+    (void) x.compare(0, 3, cs, 0, 3);
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/lwg2946.cc b/libstdc++-v3/testsuite/21_strings/basic_string/lwg2946.cc
index 3cbaf17..6e308ba 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/lwg2946.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/lwg2946.cc
@@ -29,12 +29,12 @@ int main()
   s.insert(0, {"abc", 1});
   s.replace(0, 1, {"abc", 1});
   s.replace(s.begin(), s.begin(), {"abc", 1});
-  s.find({"abc", 1});
-  s.rfind({"abc", 1});
-  s.find_first_of({"abc", 1});
-  s.find_last_of({"abc", 1});
-  s.find_first_not_of({"abc", 1});
-  s.find_last_not_of({"abc", 1});
-  s.compare({"abc", 1});
-  s.compare(0, 1, {"abc", 1});
+  (void) s.find({"abc", 1});
+  (void) s.rfind({"abc", 1});
+  (void) s.find_first_of({"abc", 1});
+  (void) s.find_last_of({"abc", 1});
+  (void) s.find_first_not_of({"abc", 1});
+  (void) s.find_last_not_of({"abc", 1});
+  (void) s.compare({"abc", 1});
+  (void) s.compare(0, 1, {"abc", 1});
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/nonnull.cc
index e987cb7..41bb391 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/contains/nonnull.cc
@@ -1,4 +1,4 @@
-// { dg-options "-std=gnu++23 -Wnonnull -O0" }
+// { dg-options "-std=gnu++23 -Wnonnull -O0 -Wno-unused-result" }
 // { dg-do compile { target c++23 } }
 
 #include <string>
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/nonnull.cc
index 1f2a156..32f3449 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/ends_with/nonnull.cc
@@ -1,4 +1,4 @@
-// { dg-options "-std=gnu++20 -Wnonnull -O0" }
+// { dg-options "-std=gnu++20 -Wnonnull -O0 -Wno-unused-result" }
 // { dg-do compile { target c++20 } }
 
 #include <string>
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/nonnull.cc
index 8514359..9e0d665 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operations/starts_with/nonnull.cc
@@ -1,4 +1,4 @@
-// { dg-options "-std=gnu++20 -Wnonnull -O0" }
+// { dg-options "-std=gnu++20 -Wnonnull -O0 -Wno-unused-result" }
 // { dg-do compile { target c++20 } }
 
 #include <string>
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operators/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operators/char/1.cc
index 704d2f6..be3e41a 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operators/char/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operators/char/1.cc
@@ -35,12 +35,12 @@ int test01(void)
   // 2:8-chars_8-chars_
   // The following triggers -Wstringop-overread.  See PR 103332.
   str1 = std::string("8-chars_") + "8-chars_";
-  str1.c_str();
+  (void) str1.c_str();
   // printf("1:%s\n", str1.c_str());
   VERIFY( str1 == "8-chars_8-chars_" );
   str2 = str1 + "7-chars";
   // printf("2:%s\n", str1.c_str()); //str1 is gone
-  str1.c_str();
+  (void) str1.c_str();
   VERIFY( str1 == "8-chars_8-chars_" );
   return 0;
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/operators/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string/operators/wchar_t/1.cc
index 4020950..df3ff7c 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/operators/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/operators/wchar_t/1.cc
@@ -32,11 +32,11 @@ int test01(void)
   // 1:8-chars_8-chars_
   // 2:8-chars_8-chars_
   str1 = std::wstring(L"8-chars_") + L"8-chars_";
-  str1.c_str();
+  (void) str1.c_str();
   // wprintf("1:%s\n", str1.c_str());
   str2 = str1 + L"7-chars";
   // wprintf("2:%s\n", str1.c_str()); //str1 is gone
-  str1.c_str();
+  (void) str1.c_str();
   return 0;
 }
 
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/1.cc
index 0376d91..3d162c6 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/capacity/1.cc
@@ -137,7 +137,7 @@ test01()
   sz03 = str02.size();
   sz04 = str02.length();
   VERIFY( sz03 == sz04 );
-  str02.data();
+  (void) str02.data();
   sz03 = str02.size();
   sz04 = str02.length();
   VERIFY( sz03 == sz04 );
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/1.cc
index 5de62ec..b27e7d7 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/1.cc
@@ -49,7 +49,7 @@ test01()
   VERIFY( cref3 == 'a' );
   try
   {
-    str01.at(csz01);
+    (void) str01.at(csz01);
     VERIFY( false ); // Should not get here, as exception thrown.
   }
   catch (std::out_of_range& fail)
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/2.cc
index e8f9db2..834d3f6 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/2.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/char/2.cc
@@ -27,5 +27,5 @@ main()
 {
   typedef std::string_view string_view_type;
   string_view_type s;
-  s[0]; // abort
+  (void) s[0]; // abort
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/1.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/1.cc
index 9877cd8..e9df872 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/1.cc
@@ -49,7 +49,7 @@ test01()
   VERIFY( cref3 == L'a' );
   try
   {
-    str01.at(csz01);
+    (void) str01.at(csz01);
     VERIFY( false ); // Should not get here, as exception thrown.
   }
   catch (std::out_of_range& fail)
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/2.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/2.cc
index 23daa7a..840de84 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/2.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/element_access/wchar_t/2.cc
@@ -29,5 +29,5 @@ main()
 {
   typedef std::wstring_view string_view_type;
   string_view_type s;
-  s[0]; // abort
+  (void) s[0]; // abort
 }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/nonnull.cc
index c0d274f..fafadcc 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/contains/nonnull.cc
@@ -1,4 +1,4 @@
-// { dg-options "-std=gnu++23 -Wnonnull -O0" }
+// { dg-options "-std=gnu++23 -Wnonnull -O0 -Wno-unused-result" }
 // { dg-do compile { target c++23 } }
 
 #include <string_view>
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/nonnull.cc
index 09a9997..50437bb 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/ends_with/nonnull.cc
@@ -1,4 +1,4 @@
-// { dg-options "-std=gnu++20 -Wnonnull -O0" }
+// { dg-options "-std=gnu++20 -Wnonnull -O0 -Wno-unused-result" }
 // { dg-do compile { target c++20 } }
 
 #include <string_view>
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/nonnull.cc
index c47f1da..fedba28a 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/operations/starts_with/nonnull.cc
@@ -1,4 +1,4 @@
-// { dg-options "-std=gnu++20 -Wnonnull -O0" }
+// { dg-options "-std=gnu++20 -Wnonnull -O0 -Wno-unused-result" }
 // { dg-do compile { target c++20 } }
 
 #include <string_view>
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/char/1.cc
index 1e8c5fd..2296fd1 100644
--- a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/char/1.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/char/1.cc
@@ -41,18 +41,18 @@ void test04()
 
   // PUT
   strb_03.str(str_01); //reset
-  strb_03.str().length();
-  strb_03.str().length();
+  (void) strb_03.str().length();
+  (void) strb_03.str().length();
   
   // streamsize sputn(const char_typs* s, streamsize n)
   // write up to n chars to out_cur from s, returning number assigned
   // NB *sputn will happily put '\0' into your stream if you give it a chance*
   str_tmp = strb_03.str();
-  str_tmp.length();
+  (void) str_tmp.length();
   strb_03.sputn("racadabras", 10);//"abracadabras or what?"
-  strb_03.str().length();
+  (void) strb_03.str().length();
   strb_03.sputn(", i wanna reach out and", 10);
-  strb_03.str().length();
+  (void) strb_03.str().length();
   str_tmp = strb_02.str();
   strb_02.sputn("racadabra", 10);
 
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/wchar_t/1.cc
index 6acc0f24..c44a535 100644
--- a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sputbackc/wchar_t/1.cc
@@ -41,18 +41,18 @@ void test04()
 
   // PUT
   strb_03.str(str_01); //reset
-  strb_03.str().length();
-  strb_03.str().length();
+  (void) strb_03.str().length();
+  (void) strb_03.str().length();
   
   // streamsize sputn(const char_typs* s, streamsize n)
   // write up to n chars to out_cur from s, returning number assigned
   // NB *sputn will happily put '\0' into your stream if you give it a chance*
   str_tmp = strb_03.str();
-  str_tmp.length();
+  (void) str_tmp.length();
   strb_03.sputn(L"racadabras", 10);//"abracadabras or what?"
-  strb_03.str().length();
+  (void) strb_03.str().length();
   strb_03.sputn(L", i wanna reach out and", 10);
-  strb_03.str().length();
+  (void) strb_03.str().length();
   str_tmp = strb_02.str();
   strb_02.sputn(L"racadabra", 10);
 
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/char/1.cc
index 2a3a28b..b4cdb17 100644
--- a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/char/1.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/char/1.cc
@@ -41,18 +41,18 @@ void test04()
 
   // PUT
   strb_03.str(str_01); //reset
-  strb_03.str().length();
-  strb_03.str().length();
+  (void) strb_03.str().length();
+  (void) strb_03.str().length();
   
   // streamsize sputn(const char_typs* s, streamsize n)
   // write up to n chars to out_cur from s, returning number assigned
   // NB *sputn will happily put '\0' into your stream if you give it a chance*
   str_tmp = strb_03.str();
-  str_tmp.length();
+  (void) str_tmp.length();
   strb_03.sputn("racadabras", 10);//"abracadabras or what?"
-  strb_03.str().length();
+  (void) strb_03.str().length();
   strb_03.sputn(", i wanna reach out and", 10);
-  strb_03.str().length();
+  (void) strb_03.str().length();
   str_tmp = strb_02.str();
   strb_02.sputn("racadabra", 10);
 
diff --git a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/wchar_t/1.cc
index 5f20e2c..eb0ae5e 100644
--- a/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/wchar_t/1.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_stringbuf/sungetc/wchar_t/1.cc
@@ -41,18 +41,18 @@ void test04()
 
   // PUT
   strb_03.str(str_01); //reset
-  strb_03.str().length();
-  strb_03.str().length();
+  (void) strb_03.str().length();
+  (void) strb_03.str().length();
   
   // streamsize sputn(const char_typs* s, streamsize n)
   // write up to n chars to out_cur from s, returning number assigned
   // NB *sputn will happily put '\0' into your stream if you give it a chance*
   str_tmp = strb_03.str();
-  str_tmp.length();
+  (void) str_tmp.length();
   strb_03.sputn(L"racadabras", 10);//"abracadabras or what?"
-  strb_03.str().length();
+  (void) strb_03.str().length();
   strb_03.sputn(L", i wanna reach out and", 10);
-  strb_03.str().length();
+  (void) strb_03.str().length();
   str_tmp = strb_02.str();
   strb_02.sputn(L"racadabra", 10);