21.link/P1227R2)  
` __cpp_lib_sstream_  from_string_view ` |  Interfacing  [ std::stringstream ](/w/cpp/io/basic_stringstream "cpp/io/basic stringstream") s with  [ std::string_view ](/w/cpp/string/basic_string_view "cpp/string/basic string view") |  202306L  |  [ ` <sstream> ` ](/w/cpp/header/sstream "cpp/header/sstream") |  (C++26)  |  [ P2495R3 ](https://wg21.link/P2495R3)  
` __cpp_lib_stacktrace ` |  [ Stacktrace library ](/w/cpp/error#Stacktrace "cpp/error") |  202011L  |  [ ` <stacktrace> ` ](/w/cpp/header/stacktrace "cpp/header/stacktrace") |  (C++23)  |  [ P0881R7 ](https://wg21.link/P0881R7)  
` __cpp_lib_start_lifetime_as ` |  Explicit lifetime management (  std::start_lifetime_as  )  |  202207L  |  [ ` <memory> ` ](/w/cpp/header/memory "cpp/header/memory") |  (C++23)  |  [ P2590R2 ](https://wg21.link/P2590R2)  
` __cpp_lib_starts_ends_with ` |  String prefix and suffix checking (  starts_with()  and  ends_with()  for  [ std::string ](/w/cpp/string/basic_string "cpp/string/basic string") and  [ std::string_view ](/w/cpp/string/basic_string_view "cpp/string/basic string view") )  |  201711L  |  [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") [ ` <string_view> ` ](/w/cpp/header/string_view "cpp/header/string view") |  (C++20)  |  [ P0457R2 ](https://wg21.link/P0457R2)  
` __cpp_lib_stdatomic_h ` |  Compatibility header for C atomic operations  |  202011L  |  [ ` <stdatomic.h> ` ](/w/cpp/header/stdatomic.h "cpp/header/stdatomic.h") |  (C++23)  |  [ P0943R6 ](https://wg21.link/P0943R6)  
` __cpp_lib_string_contains ` |  ` contains ` functions of [ ` std::basic_string ` ](/w/cpp/string/basic_string/contains "cpp/string/basic string/contains") and [ ` std::basic_string_view ` ](/w/cpp/string/basic_string_view/contains "cpp/string/basic string view/contains") |  202011L  |  [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") [ ` <string_view> ` ](/w/cpp/header/string_view "cpp/header/string view") |  (C++23)  |  [ P1679R3 ](https://wg21.link/P1679R3)  
` __cpp_lib_string_  resize_and_overwrite ` |  std::basic_string::resize_and_overwrite  |  202110L  |  [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") |  (C++23)  |  [ P1072R10 ](https://wg21.link/P1072R10)  
` __cpp_lib_string_udls ` |  [ User-defined literals for string types ](/w/cpp/string/basic_string/operator%22%22s "cpp/string/basic string/operator""s") |  201304L  |  [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") |  (C++14)  |  [ N3642 ](https://wg21.link/N3642)  
` __cpp_lib_string_view ` |  [ std::string_view ](/w/cpp/string/basic_string_view "cpp/string/basic string view") |  201606L  |  [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") [ ` <string_view> ` ](/w/cpp/header/string_view "cpp/header/string view") |  (C++17)  |  [ P0220R1 ](https://wg21.link/P0220R1)   
[ P0254R2 ](https://wg21.link/P0254R2)  
[ ConstexprIterator  ](/w/cpp/named_req/ConstexprIterator "cpp/named req/ConstexprIterator") |  201803L  |  [ ` <string> ` ](/w/cpp/header/string "cpp/header/string") [ ` <string_view> ` ](/w/cpp/header/string_view "cpp/header/string view") |  (C++20)  |  [ P0858R0 ](https://wg21.link/P0858R0)   
[ LWG3257 ](https://wg21.link/LWG3257)  
` __cpp_lib_submdspan ` |  std::submdspan  |  202306L  |  [ ` <mdspan> ` ](/w/cpp/header/mdspan "cpp/header/mdspan") |  (C++26)  |  [ P2630R4 ](https://wg21.link/P2630R4)  
` __cpp_lib_syncbuf ` |  Synchronized buffered ostream (  std::syncbuf  ,  std::osyncstream  ) and manipulators  |  201803L  |  [ ` <syncstream> ` ](/w/cpp/header/syncstream "cpp/header/syncstream") |  (C++20)  |  [ P0053R7 ](https://wg21.link/P0053R7)   
[ P0753R2 ](https://wg21.link/P0753R2)  
` __cpp_lib_text_encoding ` |  std::text_encoding  |  202306L  |  [ ` <text_encoding> ` ](/w/cpp/header/text_encoding "cpp/header/text encoding") |  (C++26)  |  [ P1885R12 ](https://wg21.link/P1885R12)  
` __cpp_lib_three_way_comparison ` |  [ Three-way comparison ](/w/cpp/language/operator_comparison#Three-way_comparis