From ec331c6db0132d11ad9ffd96aeba6053849c7db2 Mon Sep 17 00:00:00 2001 From: Hristo Hristov Date: Fri, 21 Nov 2025 09:13:28 +0200 Subject: [PATCH 1/3] [libc++][string_view] Applied `[[nodiscard]]` `[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html#apply-nodiscard-where-relevant --- libcxx/include/string_view | 137 +++++++++-------- .../string_view.nodiscard.verify.cpp | 143 +++++++++++++++++- .../strings/string.view/nonnull.verify.cpp | 6 +- 3 files changed, 218 insertions(+), 68 deletions(-) diff --git a/libcxx/include/string_view b/libcxx/include/string_view index 5ecaa3de7deba..5dd04a9ba8479 100644 --- a/libcxx/include/string_view +++ b/libcxx/include/string_view @@ -362,11 +362,11 @@ public: # endif // [string.view.iterators], iterators - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return cbegin(); } + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return cbegin(); } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return cend(); } + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return cend(); } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS return std::__make_bounded_iter(data(), data(), data() + size()); # else @@ -374,7 +374,7 @@ public: # endif } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS return std::__make_bounded_iter(data() + size(), data(), data() + size()); # else @@ -382,51 +382,54 @@ public: # endif } - _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator + rbegin() const _NOEXCEPT { return const_reverse_iterator(cend()); } - _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT { return const_reverse_iterator(cbegin()); } - _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator + crbegin() const _NOEXCEPT { return const_reverse_iterator(cend()); } - _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT { return const_reverse_iterator(cbegin()); } // [string.view.capacity], capacity - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __size_; } + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __size_; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI size_type length() const _NOEXCEPT { return __size_; } + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI size_type length() const _NOEXCEPT { return __size_; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return numeric_limits::max() / sizeof(value_type); } [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool empty() const _NOEXCEPT { return __size_ == 0; } // [string.view.access], element access - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference operator[](size_type __pos) const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference + operator[](size_type __pos) const _NOEXCEPT { return _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__pos < size(), "string_view[] index out of bounds"), __data_[__pos]; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference at(size_type __pos) const { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference at(size_type __pos) const { return __pos >= size() ? (__throw_out_of_range("string_view::at"), __data_[0]) : __data_[__pos]; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference front() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference front() const _NOEXCEPT { return _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "string_view::front(): string is empty"), __data_[0]; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference back() const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_reference back() const _NOEXCEPT { return _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "string_view::back(): string is empty"), __data_[__size_ - 1]; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_pointer data() const _NOEXCEPT { return __data_; } + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI const_pointer data() const _NOEXCEPT { return __data_; } // [string.view.modifiers], modifiers: _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI void remove_prefix(size_type __n) _NOEXCEPT { @@ -459,7 +462,8 @@ public: return __rlen; } - _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI basic_string_view substr(size_type __pos = 0, size_type __n = npos) const { + [[__nodiscard__]] _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI basic_string_view + substr(size_type __pos = 0, size_type __n = npos) const { // Use the `__assume_valid` form of the constructor to avoid an unnecessary check. Any substring of a view is a // valid view. In particular, `size()` is known to be smaller than `numeric_limits::max()`, so the // new size is also smaller. See also https://llvm.org/PR91634. @@ -474,7 +478,7 @@ public: } # endif - _LIBCPP_CONSTEXPR_SINCE_CXX14 int compare(basic_string_view __sv) const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 int compare(basic_string_view __sv) const _NOEXCEPT { size_type __rlen = std::min(size(), __sv.size()); int __retval = _Traits::compare(data(), __sv.data(), __rlen); if (__retval == 0) // first __rlen chars matched @@ -482,50 +486,51 @@ public: return __retval; } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int compare(size_type __pos1, size_type __n1, basic_string_view __sv) const { return substr(__pos1, __n1).compare(__sv); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int compare(size_type __pos1, size_type __n1, basic_string_view __sv, size_type __pos2, size_type __n2) const { return substr(__pos1, __n1).compare(__sv.substr(__pos2, __n2)); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int compare(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s) const _NOEXCEPT { return compare(basic_string_view(__s)); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int compare(size_type __pos1, size_type __n1, const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s) const { return substr(__pos1, __n1).compare(basic_string_view(__s)); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI int compare(size_type __pos1, size_type __n1, const _CharT* __s, size_type __n2) const _LIBCPP_DIAGNOSE_NULLPTR_IF(__n2 != 0 && __s == nullptr, " if n2 is not zero") { return substr(__pos1, __n1).compare(basic_string_view(__s, __n2)); } // find - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find(basic_string_view __s, size_type __pos = 0) const _NOEXCEPT { return std::__str_find(data(), size(), __s.data(), __pos, __s.size()); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find(_CharT __c, size_type __pos = 0) const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + find(_CharT __c, size_type __pos = 0) const _NOEXCEPT { return std::__str_find(data(), size(), __c, __pos); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find(const _CharT* __s, size_type __pos, size_type __n) const _NOEXCEPT _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") { _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "string_view::find(): received nullptr"); return std::__str_find(data(), size(), __s, __pos, __n); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, size_type __pos = 0) const _NOEXCEPT { _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string_view::find(): received nullptr"); return std::__str_find( @@ -533,24 +538,24 @@ public: } // rfind - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type rfind(basic_string_view __s, size_type __pos = npos) const _NOEXCEPT { return std::__str_rfind(data(), size(), __s.data(), __pos, __s.size()); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type rfind(_CharT __c, size_type __pos = npos) const _NOEXCEPT { return std::__str_rfind(data(), size(), __c, __pos); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type rfind(const _CharT* __s, size_type __pos, size_type __n) const _NOEXCEPT _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") { _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "string_view::rfind(): received nullptr"); return std::__str_rfind(data(), size(), __s, __pos, __n); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type rfind(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, size_type __pos = npos) const _NOEXCEPT { _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string_view::rfind(): received nullptr"); return std::__str_rfind( @@ -558,25 +563,25 @@ public: } // find_first_of - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_of(basic_string_view __s, size_type __pos = 0) const _NOEXCEPT { return std::__str_find_first_of( data(), size(), __s.data(), __pos, __s.size()); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_of(_CharT __c, size_type __pos = 0) const _NOEXCEPT { return find(__c, __pos); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_of(const _CharT* __s, size_type __pos, size_type __n) const _NOEXCEPT _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") { _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "string_view::find_first_of(): received nullptr"); return std::__str_find_first_of(data(), size(), __s, __pos, __n); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_of(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, size_type __pos = 0) const _NOEXCEPT { _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string_view::find_first_of(): received nullptr"); return std::__str_find_first_of( @@ -584,25 +589,25 @@ public: } // find_last_of - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_of(basic_string_view __s, size_type __pos = npos) const _NOEXCEPT { return std::__str_find_last_of( data(), size(), __s.data(), __pos, __s.size()); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_of(_CharT __c, size_type __pos = npos) const _NOEXCEPT { return rfind(__c, __pos); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_of(const _CharT* __s, size_type __pos, size_type __n) const _NOEXCEPT _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") { _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "string_view::find_last_of(): received nullptr"); return std::__str_find_last_of(data(), size(), __s, __pos, __n); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_of(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, size_type __pos = npos) const _NOEXCEPT { _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string_view::find_last_of(): received nullptr"); return std::__str_find_last_of( @@ -610,25 +615,25 @@ public: } // find_first_not_of - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_not_of(basic_string_view __s, size_type __pos = 0) const _NOEXCEPT { return std::__str_find_first_not_of( data(), size(), __s.data(), __pos, __s.size()); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_not_of(_CharT __c, size_type __pos = 0) const _NOEXCEPT { return std::__str_find_first_not_of(data(), size(), __c, __pos); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_not_of(const _CharT* __s, size_type __pos, size_type __n) const _NOEXCEPT _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") { _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "string_view::find_first_not_of(): received nullptr"); return std::__str_find_first_not_of(data(), size(), __s, __pos, __n); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_first_not_of(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, size_type __pos = 0) const _NOEXCEPT { _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string_view::find_first_not_of(): received nullptr"); return std::__str_find_first_not_of( @@ -636,25 +641,25 @@ public: } // find_last_not_of - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_not_of(basic_string_view __s, size_type __pos = npos) const _NOEXCEPT { return std::__str_find_last_not_of( data(), size(), __s.data(), __pos, __s.size()); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_not_of(_CharT __c, size_type __pos = npos) const _NOEXCEPT { return std::__str_find_last_not_of(data(), size(), __c, __pos); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_not_of(const _CharT* __s, size_type __pos, size_type __n) const _NOEXCEPT _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") { _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "string_view::find_last_not_of(): received nullptr"); return std::__str_find_last_not_of(data(), size(), __s, __pos, __n); } - _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type + [[__nodiscard__]] _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI size_type find_last_not_of(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, size_type __pos = npos) const _NOEXCEPT { _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "string_view::find_last_not_of(): received nullptr"); return std::__str_find_last_not_of( @@ -662,37 +667,43 @@ public: } # if _LIBCPP_STD_VER >= 20 - constexpr _LIBCPP_HIDE_FROM_ABI bool starts_with(basic_string_view __s) const noexcept { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool starts_with(basic_string_view __s) const noexcept { return size() >= __s.size() && compare(0, __s.size(), __s) == 0; } - constexpr _LIBCPP_HIDE_FROM_ABI bool starts_with(value_type __c) const noexcept { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool starts_with(value_type __c) const noexcept { return !empty() && _Traits::eq(front(), __c); } - constexpr _LIBCPP_HIDE_FROM_ABI bool starts_with(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s) const noexcept { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool + starts_with(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s) const noexcept { return starts_with(basic_string_view(__s)); } - constexpr _LIBCPP_HIDE_FROM_ABI bool ends_with(basic_string_view __s) const noexcept { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool ends_with(basic_string_view __s) const noexcept { return size() >= __s.size() && compare(size() - __s.size(), npos, __s) == 0; } - constexpr _LIBCPP_HIDE_FROM_ABI bool ends_with(value_type __c) const noexcept { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool ends_with(value_type __c) const noexcept { return !empty() && _Traits::eq(back(), __c); } - constexpr _LIBCPP_HIDE_FROM_ABI bool ends_with(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s) const noexcept { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool + ends_with(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s) const noexcept { return ends_with(basic_string_view(__s)); } # endif # if _LIBCPP_STD_VER >= 23 - constexpr _LIBCPP_HIDE_FROM_ABI bool contains(basic_string_view __sv) const noexcept { return find(__sv) != npos; } + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool contains(basic_string_view __sv) const noexcept { + return find(__sv) != npos; + } - constexpr _LIBCPP_HIDE_FROM_ABI bool contains(value_type __c) const noexcept { return find(__c) != npos; } + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool contains(value_type __c) const noexcept { + return find(__c) != npos; + } - constexpr _LIBCPP_HIDE_FROM_ABI bool contains(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s) const { + [[nodiscard]] constexpr _LIBCPP_HIDE_FROM_ABI bool contains(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s) const { return find(__s) != npos; } # endif @@ -897,7 +908,8 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, basic_string_view<_CharT, _Trai // [string.view.hash] template struct __string_view_hash : public __unary_function >, size_t> { - _LIBCPP_HIDE_FROM_ABI size_t operator()(const basic_string_view<_CharT, char_traits<_CharT> > __val) const _NOEXCEPT { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_t + operator()(const basic_string_view<_CharT, char_traits<_CharT> > __val) const _NOEXCEPT { return std::__do_string_hash(__val.data(), __val.data() + __val.size()); } }; @@ -924,30 +936,31 @@ struct hash > > : __string_view_ # if _LIBCPP_STD_VER >= 14 inline namespace literals { inline namespace string_view_literals { -inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view operator""sv(const char* __str, size_t __len) noexcept { +[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view +operator""sv(const char* __str, size_t __len) noexcept { return basic_string_view(__str, __len); } # if _LIBCPP_HAS_WIDE_CHARACTERS -inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view +[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view operator""sv(const wchar_t* __str, size_t __len) noexcept { return basic_string_view(__str, __len); } # endif # if _LIBCPP_HAS_CHAR8_T -inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view +[[nodiscard]] inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view operator""sv(const char8_t* __str, size_t __len) noexcept { return basic_string_view(__str, __len); } # endif -inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view +[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view operator""sv(const char16_t* __str, size_t __len) noexcept { return basic_string_view(__str, __len); } -inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view +[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string_view operator""sv(const char32_t* __str, size_t __len) noexcept { return basic_string_view(__str, __len); } diff --git a/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp index e5b2258315fe4..d027c32e90000 100644 --- a/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp +++ b/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp @@ -12,12 +12,147 @@ #include +#include "type_algorithms.h" #include "test_macros.h" -void test() { - std::string_view string_view; - string_view.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +void test_members() { + std::string_view sv; + + sv.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.crbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.crend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv.size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.length(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv[0]; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.at(0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv.front(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.back(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.data(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv.substr(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} #if TEST_STD_VER >= 26 - string_view.subview(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.subview(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.compare(sv); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.compare(0, 0, sv); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.compare(0, 0, sv, 0, 0); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.compare(""); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.compare(0, 0, ""); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.compare(0, 0, "", 0); + + sv.find(sv); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find(' '); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find("", 0, 0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find("", 0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv.rfind(sv); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.rfind(' '); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.rfind("", 0, 0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.rfind("", 0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_of(sv); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_of(' '); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_of("", 0, 0); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_of("", 0); + + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_of(sv); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_of(' '); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_of("", 0, 0); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_of("", 0); + + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_not_of(sv); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_not_of(' '); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_not_of("", 0, 0); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_first_not_of("", 0); + + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_not_of(sv); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_not_of(' '); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_not_of("", 0, 0); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.find_last_not_of("", 0); + +#if TEST_STD_VER >= 20 + sv.starts_with(sv); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.starts_with(' '); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.starts_with(""); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + sv.ends_with(sv); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.ends_with(' '); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.ends_with(""); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + +#if TEST_STD_VER >= 23 + sv.contains(sv); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.contains(' '); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + sv.contains(""); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif +} + +class TestHash { +public: + template + void operator()() { + using StringViewT = std::basic_string_view; + std::hash hash; + // expected-warning@+1 4-5 {{ignoring return value of function declared with 'nodiscard' attribute}} + hash(StringViewT{}); + } +}; + +void test_nonmembers() { + // std::hash<> + types::for_each(types::character_types(), TestHash{}); + +#if TEST_STD_VER >= 14 + // string_view literals + using namespace std::string_view_literals; + + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + ""sv; // const char* +# if !defined(TEST_HAS_NO_WIDE_CHARACTERS) + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + L""sv; // const wchar_t* +# endif +# if !defined(TEST_HAS_NO_CHAR8_T) + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + u8""sv; // const char8_t* +# endif + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + u""sv; // const char16_t* + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + U""sv; // const char32_t* #endif } diff --git a/libcxx/test/libcxx/strings/string.view/nonnull.verify.cpp b/libcxx/test/libcxx/strings/string.view/nonnull.verify.cpp index 316c9828e0de5..ffe048730e687 100644 --- a/libcxx/test/libcxx/strings/string.view/nonnull.verify.cpp +++ b/libcxx/test/libcxx/strings/string.view/nonnull.verify.cpp @@ -10,8 +10,10 @@ // Ensure that APIs which take a CharT* are diagnosing passing a nullptr to them -// Clang 19 and AppleClang don't have diagnose_if with diagnostic flags -// UNSUPPORTED: clang-19, apple-clang-17 +// AppleClang doesn't have diagnose_if with diagnostic flags +// UNSUPPORTED: apple-clang-17 + +// ADDITIONAL_COMPILE_FLAGS: -Wno-unused-result #include From 8962d8bfbfe5851d868f6dfb4508c2de2850e7b8 Mon Sep 17 00:00:00 2001 From: Hristo Hristov Date: Mon, 24 Nov 2025 12:47:27 +0200 Subject: [PATCH 2/3] Addressed review comment --- .../diagnostics/string_view.nodiscard.verify.cpp | 15 +++------------ 1 file changed, 3 insertions(+), 12 deletions(-) diff --git a/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp index d027c32e90000..44787db4d5352 100644 --- a/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp +++ b/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp @@ -121,20 +121,11 @@ void test_members() { #endif } -class TestHash { -public: - template - void operator()() { - using StringViewT = std::basic_string_view; - std::hash hash; - // expected-warning@+1 4-5 {{ignoring return value of function declared with 'nodiscard' attribute}} - hash(StringViewT{}); - } -}; - void test_nonmembers() { // std::hash<> - types::for_each(types::character_types(), TestHash{}); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + std::hash hash; + hash(); #if TEST_STD_VER >= 14 // string_view literals From f2913cafc135513c9d23d0c825b3a2631d107bd2 Mon Sep 17 00:00:00 2001 From: Hristo Hristov Date: Mon, 24 Nov 2025 13:25:55 +0200 Subject: [PATCH 3/3] Fix build --- .../libcxx/diagnostics/string_view.nodiscard.verify.cpp | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp index 44787db4d5352..89e4a5b44ab48 100644 --- a/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp +++ b/libcxx/test/libcxx/diagnostics/string_view.nodiscard.verify.cpp @@ -123,12 +123,14 @@ void test_members() { void test_nonmembers() { // std::hash<> - // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + std::hash hash; - hash(); + // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}} + hash(std::string_view{}); #if TEST_STD_VER >= 14 // string_view literals + using namespace std::string_view_literals; // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}