[libc++] Inline small constructors into basic_string

[philnik]

Summary

This allows the compiler to inline the constructors.

[Mordante]

In general I like this. Did you see a change in binary size or performance with this change?

libcxx/include/string

1003

Has this change an effect due to the _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS?

1064–1068

This changes the indention.

[philnik]

In D144580#4152448, @Mordante wrote:

In general I like this. Did you see a change in binary size or performance with this change?

I don't have a large code base to check, but here is a small example: https://godbolt.org/z/oYj76b78K (everything is implicitly inline because of constexpr in C++20)

libcxx/include/string

1003

No, I missed these ones in D128081.

[Mordante]

In D144580#4152479, @philnik wrote:

In D144580#4152448, @Mordante wrote:

In general I like this. Did you see a change in binary size or performance with this change?

I don't have a large code base to check, but here is a small example: https://godbolt.org/z/oYj76b78K (everything is implicitly inline because of constexpr in C++20)

This looks nice :-)

I see the patch failed to apply in the CI, can you fix that?

No other comments, but I like to see a CI run before approving.

libcxx/include/string

1003

Thanks.

[philnik]

Rebased

[ldionne]

LGTM w/ green CI.

[philnik]

Rebased

libcxx/include/string

 #else
       _NOEXCEPT
 #endif
       : __r_(__default_init_tag(), __a) {
     std::__debug_db_insert_c(this);
     __default_init();
   }
 
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const basic_string& __str);
-  _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const basic_string& __str, const allocator_type& __a);
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const basic_string& __str)
+      : __r_(__default_init_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc())) {
+    if (!__str.__is_long())
+      __r_.first() = __str.__r_.first();
+    else
+      __init_copy_ctor_external(std::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
+    std::__debug_db_insert_c(this);
+  }
+
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const basic_string& __str, const allocator_type& __a)
+      : __r_(__default_init_tag(), __a) {
+    if (!__str.__is_long())
+      __r_.first() = __str.__r_.first();
+    else
+      __init_copy_ctor_external(std::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
+    std::__debug_db_insert_c(this);
+  }
 
 #ifndef _LIBCPP_CXX03_LANG
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(basic_string&& __str)
 #  if _LIBCPP_STD_VER <= 14
       _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
 #  else
       _NOEXCEPT
 #  endif
#endif // _LIBCPP_CXX03_LANG
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const _CharT* __s)
       : __r_(__default_init_tag(), __default_init_tag()) {
     _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
     __init(__s, traits_type::length(__s));
     std::__debug_db_insert_c(this);
   }
 
   template <__enable_if_t<__is_allocator<_Allocator>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const _CharT* __s, const _Allocator& __a);
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const _CharT* __s, const _Allocator& __a)
+      : __r_(__default_init_tag(), __a) {
+    _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
+    __init(__s, traits_type::length(__s));
+    std::__debug_db_insert_c(this);
+  }
 
 #if _LIBCPP_STD_VER >= 23
   basic_string(nullptr_t) = delete;
 #endif
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const _CharT* __s, size_type __n)
       : __r_(__default_init_tag(), __default_init_tag()) {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
basic_string(basic_string&& __str, size_type __pos, size_type __n, const _Allocator& __alloc = _Allocator())
 
     std::__debug_db_insert_c(this);
     if (__is_long())
       std::__debug_db_swap(this, &__str);
   }
 #endif
 
   template <__enable_if_t<__is_allocator<_Allocator>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(size_type __n, _CharT __c, const _Allocator& __a);
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(size_type __n, _CharT __c, const _Allocator& __a)
+      : __r_(__default_init_tag(), __a) {
+    __init(__n, __c);
+    std::__debug_db_insert_c(this);
+  }
 
   _LIBCPP_CONSTEXPR_SINCE_CXX20
-  basic_string(const basic_string& __str, size_type __pos, size_type __n, const _Allocator& __a = _Allocator());
+  basic_string(const basic_string& __str, size_type __pos, size_type __n, const _Allocator& __a = _Allocator())
+      : __r_(__default_init_tag(), __a) {
+    size_type __str_sz = __str.size();
+    if (__pos > __str_sz)
+      __throw_out_of_range();
+    __init(__str.data() + __pos, std::min(__n, __str_sz - __pos));
+    std::__debug_db_insert_c(this);
+  }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
   basic_string(const basic_string& __str, size_type __pos, const _Allocator& __a = _Allocator())
       : __r_(__default_init_tag(), __a) {
     size_type __str_sz = __str.size();
     if (__pos > __str_sz)
       __throw_out_of_range();
     __init(__str.data() + __pos, __str_sz - __pos);
     std::__debug_db_insert_c(this);
   }
 
   template <class _Tp,
             __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
-                              !__is_same_uncvref<_Tp, basic_string>::value, int> = 0>
+                              !__is_same_uncvref<_Tp, basic_string>::value,
+                          int> = 0>
   _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS _LIBCPP_CONSTEXPR_SINCE_CXX20
-  basic_string(const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a = allocator_type());
+  basic_string(const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a = allocator_type())
+      : __r_(__default_init_tag(), __a) {
+    __self_view __sv0 = __t;
+    __self_view __sv  = __sv0.substr(__pos, __n);
+    __init(__sv.data(), __sv.size());
+    std::__debug_db_insert_c(this);
+  }
 
   template <class _Tp,
             __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
-                              !__is_same_uncvref<_Tp, basic_string>::value, int> = 0>
-  _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(
-      const _Tp& __t);
+                              !__is_same_uncvref<_Tp, basic_string>::value,
+                          int> = 0>
+  _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(const _Tp& __t)
+      : __r_(__default_init_tag(), __default_init_tag()) {
+    __self_view __sv = __t;
+    __init(__sv.data(), __sv.size());
+    std::__debug_db_insert_c(this);
+  }
 
   template <class _Tp,
             __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
-                              !__is_same_uncvref<_Tp, basic_string>::value, int> = 0>
+                              !__is_same_uncvref<_Tp, basic_string>::value,
+                          int> = 0>
   _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(
-      const _Tp& __t, const allocator_type& __a);
+      const _Tp& __t, const allocator_type& __a)
+      : __r_(__default_init_tag(), __a) {
+    __self_view __sv = __t;
+    __init(__sv.data(), __sv.size());
+    std::__debug_db_insert_c(this);
+  }
 
   template <class _InputIterator, __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(_InputIterator __first, _InputIterator __last)
       : __r_(__default_init_tag(), __default_init_tag()) {
     __init(__first, __last);
     std::__debug_db_insert_c(this);
   }
 
#ifndef _LIBCPP_CXX03_LANG
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(initializer_list<_CharT> __il, const _Allocator& __a)
       : __r_(__default_init_tag(), __a) {
     __init(__il.begin(), __il.end());
     std::__debug_db_insert_c(this);
   }
 #endif // _LIBCPP_CXX03_LANG
 
-    inline _LIBCPP_CONSTEXPR_SINCE_CXX20 ~basic_string();
+  inline _LIBCPP_CONSTEXPR_SINCE_CXX20 ~basic_string() {
+    std::__debug_db_erase_c(this);
+    if (__is_long())
+      __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
+  }
 
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
     operator __self_view() const _NOEXCEPT { return __self_view(data(), size()); }
 
     _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& operator=(const basic_string& __str);
 
     template <class _Tp, __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
                                            !__is_same_uncvref<_Tp, basic_string>::value, int> = 0>
else
         __set_long_cap(__allocation.count);
         __set_long_size(__sz);
     }
     traits_type::copy(std::__to_address(__p), __s, __sz);
     traits_type::assign(__p[__sz], value_type());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-template <__enable_if_t<__is_allocator<_Allocator>::value, int> >
-_LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a)
-    : __r_(__default_init_tag(), __a)
-{
-    _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
-    __init(__s, traits_type::length(__s));
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
-    : __r_(__default_init_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc()))
-{
-    if (!__str.__is_long())
-        __r_.first() = __str.__r_.first();
-    else
-        __init_copy_ctor_external(std::__to_address(__str.__get_long_pointer()),
-                                  __str.__get_long_size());
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::basic_string(
-    const basic_string& __str, const allocator_type& __a)
-    : __r_(__default_init_tag(), __a)
-{
-    if (!__str.__is_long())
-        __r_.first() = __str.__r_.first();
-    else
-        __init_copy_ctor_external(std::__to_address(__str.__get_long_pointer()),
-                                  __str.__get_long_size());
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20
 void basic_string<_CharT, _Traits, _Allocator>::__init_copy_ctor_external(
     const value_type* __s, size_type __sz) {
   if (__libcpp_is_constant_evaluated())
     __r_.first() = __rep();
 
   pointer __p;
   if (__fits_in_sso(__sz)) {
else
         __set_long_cap(__allocation.count);
         __set_long_size(__n);
     }
     traits_type::assign(std::__to_address(__p), __n, __c);
     traits_type::assign(__p[__n], value_type());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-template <__enable_if_t<__is_allocator<_Allocator>::value, int> >
-_LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a)
-    : __r_(__default_init_tag(), __a)
-{
-    __init(__n, __c);
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str,
-                                                        size_type __pos, size_type __n,
-                                                        const _Allocator& __a)
-    : __r_(__default_init_tag(), __a)
-{
-    size_type __str_sz = __str.size();
-    if (__pos > __str_sz)
-        __throw_out_of_range();
-    __init(__str.data() + __pos, std::min(__n, __str_sz - __pos));
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-template <class _Tp,
-          __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
-                            !__is_same_uncvref<_Tp, basic_string<_CharT, _Traits, _Allocator> >::value,
-                        int> >
-_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<_CharT, _Traits, _Allocator>::basic_string(
-    const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a)
-    : __r_(__default_init_tag(), __a) {
-    __self_view __sv0 = __t;
-    __self_view __sv = __sv0.substr(__pos, __n);
-    __init(__sv.data(), __sv.size());
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-template <class _Tp,
-          __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
-                            !__is_same_uncvref<_Tp, basic_string<_CharT, _Traits, _Allocator> >::value,
-                        int> >
-_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp& __t)
-    : __r_(__default_init_tag(), __default_init_tag()) {
-    __self_view __sv = __t;
-    __init(__sv.data(), __sv.size());
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-template <class _Tp,
-          __enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
-                            !__is_same_uncvref<_Tp, basic_string<_CharT, _Traits, _Allocator> >::value,
-                        int> >
-_LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp& __t, const _Allocator& __a)
-    : __r_(__default_init_tag(), __a) {
-    __self_view __sv = __t;
-    __init(__sv.data(), __sv.size());
-    std::__debug_db_insert_c(this);
-}
-
-template <class _CharT, class _Traits, class _Allocator>
 template <class _InputIterator, __enable_if_t<__is_exactly_cpp17_input_iterator<_InputIterator>::value, int> >
 _LIBCPP_CONSTEXPR_SINCE_CXX20
 void basic_string<_CharT, _Traits, _Allocator>::__init(_InputIterator __first, _InputIterator __last)
 {
     __default_init();
 #ifndef _LIBCPP_HAS_NO_EXCEPTIONS
     try
     {
catch (...)
             __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
         throw;
     }
 #endif  // _LIBCPP_HAS_NO_EXCEPTIONS
 }
 
 template <class _CharT, class _Traits, class _Allocator>
 _LIBCPP_CONSTEXPR_SINCE_CXX20
-basic_string<_CharT, _Traits, _Allocator>::~basic_string()
-{
-    std::__debug_db_erase_c(this);
-    if (__is_long())
-        __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap());
-}
-
-template <class _CharT, class _Traits, class _Allocator>
-_LIBCPP_CONSTEXPR_SINCE_CXX20
 void
 basic_string<_CharT, _Traits, _Allocator>::__grow_by_and_replace
     (size_type __old_cap, size_type __delta_cap, size_type __old_sz,
      size_type __n_copy,  size_type __n_del,     size_type __n_add, const value_type* __p_new_stuff)
 {
     size_type __ms = max_size();
     if (__delta_cap > __ms - __old_cap - 1)
         __throw_length_error();