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[libc++][string] Applied [[nodiscard]] to non-member functions #169330

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Nov 25, 2025
+130 −46
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[libc++][string] Applied [[nodiscard]] to non-member functions #169330

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99 changes: 53 additions & 46 deletions libcxx/include/string
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Original file line number Diff line number Diff line change
Expand Up @@ -3851,46 +3851,52 @@ swap(basic_string<_CharT, _Traits, _Allocator>& __lhs, basic_string<_CharT, _Tra
__lhs.swap(__rhs);
}

_LIBCPP_EXPORTED_FROM_ABI int stoi(const string& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI long stol(const string& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI unsigned long stoul(const string& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI long long stoll(const string& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI unsigned long long stoull(const string& __str, size_t* __idx = nullptr, int __base = 10);

_LIBCPP_EXPORTED_FROM_ABI float stof(const string& __str, size_t* __idx = nullptr);
_LIBCPP_EXPORTED_FROM_ABI double stod(const string& __str, size_t* __idx = nullptr);
_LIBCPP_EXPORTED_FROM_ABI long double stold(const string& __str, size_t* __idx = nullptr);

_LIBCPP_EXPORTED_FROM_ABI string to_string(int __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(unsigned __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(long __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(unsigned long __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(long long __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(unsigned long long __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(float __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(double __val);
_LIBCPP_EXPORTED_FROM_ABI string to_string(long double __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI int stoi(const string& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI unsigned long
stoul(const string& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long stol(const string& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long long
stoll(const string& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI unsigned long long
stoull(const string& __str, size_t* __idx = nullptr, int __base = 10);

[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI float stof(const string& __str, size_t* __idx = nullptr);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI double stod(const string& __str, size_t* __idx = nullptr);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long double stold(const string& __str, size_t* __idx = nullptr);

[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(int __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(unsigned __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(unsigned long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(long long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(unsigned long long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(float __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(double __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI string to_string(long double __val);

# if _LIBCPP_HAS_WIDE_CHARACTERS
_LIBCPP_EXPORTED_FROM_ABI int stoi(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI long stol(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI unsigned long stoul(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI long long stoll(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
_LIBCPP_EXPORTED_FROM_ABI unsigned long long stoull(const wstring& __str, size_t* __idx = nullptr, int __base = 10);

_LIBCPP_EXPORTED_FROM_ABI float stof(const wstring& __str, size_t* __idx = nullptr);
_LIBCPP_EXPORTED_FROM_ABI double stod(const wstring& __str, size_t* __idx = nullptr);
_LIBCPP_EXPORTED_FROM_ABI long double stold(const wstring& __str, size_t* __idx = nullptr);

_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(int __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned long __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long long __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned long long __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(float __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(double __val);
_LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long double __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI int stoi(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long stol(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI unsigned long
stoul(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long long
stoll(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI unsigned long long
stoull(const wstring& __str, size_t* __idx = nullptr, int __base = 10);

[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI float stof(const wstring& __str, size_t* __idx = nullptr);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI double stod(const wstring& __str, size_t* __idx = nullptr);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI long double stold(const wstring& __str, size_t* __idx = nullptr);

[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(int __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(unsigned long long __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(float __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(double __val);
[[__nodiscard__]] _LIBCPP_EXPORTED_FROM_ABI wstring to_wstring(long double __val);
# endif // _LIBCPP_HAS_WIDE_CHARACTERS

template <class _CharT, class _Traits, class _Allocator>
Expand All @@ -3899,7 +3905,7 @@ _LIBCPP_TEMPLATE_DATA_VIS const typename basic_string<_CharT, _Traits, _Allocato

template <class _CharT, class _Allocator>
struct __string_hash : public __unary_function<basic_string<_CharT, char_traits<_CharT>, _Allocator>, size_t> {
_LIBCPP_HIDE_FROM_ABI size_t
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_t
operator()(const basic_string<_CharT, char_traits<_CharT>, _Allocator>& __val) const _NOEXCEPT {
return std::__do_string_hash(__val.data(), __val.data() + __val.size());
}
Expand Down Expand Up @@ -3970,30 +3976,31 @@ erase_if(basic_string<_CharT, _Traits, _Allocator>& __str, _Predicate __pred) {
// Literal suffixes for basic_string [basic.string.literals]
inline namespace literals {
inline namespace string_literals {
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<char>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<char>
operator""s(const char* __str, size_t __len) {
return basic_string<char>(__str, __len);
}

# if _LIBCPP_HAS_WIDE_CHARACTERS
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<wchar_t>
operator""s(const wchar_t* __str, size_t __len) {
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<wchar_t> operator""s(const wchar_t* __str, size_t __len) {
return basic_string<wchar_t>(__str, __len);
}
# endif

# if _LIBCPP_HAS_CHAR8_T
inline _LIBCPP_HIDE_FROM_ABI constexpr basic_string<char8_t> operator""s(const char8_t* __str, size_t __len) {
[[__nodiscard__]] inline
_LIBCPP_HIDE_FROM_ABI constexpr basic_string<char8_t> operator""s(const char8_t* __str, size_t __len) {
return basic_string<char8_t>(__str, __len);
}
# endif

inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<char16_t>
operator""s(const char16_t* __str, size_t __len) {
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<char16_t> operator""s(const char16_t* __str, size_t __len) {
return basic_string<char16_t>(__str, __len);
}

inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<char32_t>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<char32_t>
operator""s(const char32_t* __str, size_t __len) {
return basic_string<char32_t>(__str, __len);
}
Expand Down
77 changes: 77 additions & 0 deletions libcxx/test/libcxx/diagnostics/string.nodiscard.verify.cpp
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -130,3 +130,80 @@ void test() {
str.subview(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
#endif
}

void test_nonmembers() {
// Numeric conversions

std::string str;

std::stoi(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stol(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stoll(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stoull(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

std::stof(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stod(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stold(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

std::to_string(94); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(82U); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(94L); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(82UL); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(94LL); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(82ULL); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(94.0F); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(82.0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_string(94.0L); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

#if !defined(TEST_HAS_NO_WIDE_CHARACTERS)

std::wstring wstr;

std::stoi(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stol(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stoll(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stoull(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

std::stof(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stod(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::stold(wstr); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

std::to_wstring(94); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(82U); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(94L); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(82UL); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(94LL); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(82ULL); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(94.0F); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(82.0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::to_wstring(94.0L); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

#endif

// std::hash<>

std::hash<std::string> hash;

hash(str); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

#if TEST_STD_VER >= 14
// string literals

using namespace std::string_literals;

// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
""s; // const char*
# if !defined(TEST_HAS_NO_WIDE_CHARACTERS)
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
L""s; // const wchar_t*
# endif
# if !defined(TEST_HAS_NO_CHAR8_T)
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
u8""s; // const char8_t*
# endif
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
u""s; // const char16_t*
// expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
U""s; // const char32_t*
#endif
}
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