[libcxx-commits] [libcxx] [libc++] Default the allocator argument for most constructors (PR #169901)

[via libcxx-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

<details>
<summary>Changes</summary>

Allocators are generally very cheap to copy, so avoiding copies by having separate overloads is not that useful. Defaulting them significanlty reduces the overload set the compiler has to consider and simplifies the code, since we can remove some functions in the future.


---
Full diff: https://github.com/llvm/llvm-project/pull/169901.diff


3 Files Affected:

- (modified) libcxx/include/string (+9-38) 
- (modified) libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp (-3) 
- (modified) libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp (-3) 


``````````diff
diff --git a/libcxx/include/string b/libcxx/include/string
index 2b3ba6d2d9b62..ea90be950ba11 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -1058,15 +1058,9 @@ public:
   }
 #  endif // _LIBCPP_CXX03_LANG
 
-  template <__enable_if_t<__is_allocator_v<_Allocator>, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s) {
-    _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "basic_string(const char*) detected nullptr");
-    __init(__s, traits_type::length(__s));
-  }
-
   template <__enable_if_t<__is_allocator_v<_Allocator>, int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
-  basic_string(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, const _Allocator& __a)
+  basic_string(const _CharT* _LIBCPP_DIAGNOSE_NULLPTR __s, const _Allocator& __a = _Allocator())
       : __alloc_(__a) {
     _LIBCPP_ASSERT_NON_NULL(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
     __init(__s, traits_type::length(__s));
@@ -1076,22 +1070,14 @@ public:
   basic_string(nullptr_t) = delete;
 #  endif
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(const _CharT* __s, size_type __n)
-      _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero") {
-    _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
-    __init(__s, __n);
-  }
-
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
-  basic_string(const _CharT* __s, size_type __n, const _Allocator& __a)
+  basic_string(const _CharT* __s, size_type __n, const _Allocator& __a = _Allocator())
       _LIBCPP_DIAGNOSE_NULLPTR_IF(__n != 0 && __s == nullptr, " if n is not zero")
       : __alloc_(__a) {
     _LIBCPP_ASSERT_NON_NULL(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
     __init(__s, __n);
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(size_type __n, _CharT __c) { __init(__n, __c); }
-
 #  if _LIBCPP_STD_VER >= 23
   _LIBCPP_HIDE_FROM_ABI constexpr basic_string(
       basic_string&& __str, size_type __pos, const _Allocator& __alloc = _Allocator())
@@ -1114,7 +1100,8 @@ public:
 #  endif
 
   template <__enable_if_t<__is_allocator_v<_Allocator>, 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 = _Allocator())
       : __alloc_(__a) {
     __init(__n, __c);
   }
@@ -1153,29 +1140,16 @@ public:
             __enable_if_t<__can_be_converted_to_string_view_v<_CharT, _Traits, _Tp> &&
                               !is_same<__remove_cvref_t<_Tp>, basic_string>::value,
                           int> = 0>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(const _Tp& __t) {
-    __self_view __sv = __t;
-    __init(__sv.data(), __sv.size());
-  }
-
-  template <class _Tp,
-            __enable_if_t<__can_be_converted_to_string_view_v<_CharT, _Traits, _Tp> &&
-                              !is_same<__remove_cvref_t<_Tp>, basic_string>::value,
-                          int> = 0>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(const _Tp& __t, const allocator_type& __a)
+  _LIBCPP_HIDE_FROM_ABI
+  _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(const _Tp& __t, const allocator_type& __a = allocator_type())
       : __alloc_(__a) {
     __self_view __sv = __t;
     __init(__sv.data(), __sv.size());
   }
 
-  template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(_InputIterator __first, _InputIterator __last) {
-    __init(__first, __last);
-  }
-
   template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
-  basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a)
+  basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a = allocator_type())
       : __alloc_(__a) {
     __init(__first, __last);
   }
@@ -1194,11 +1168,8 @@ public:
 #  endif
 
 #  ifndef _LIBCPP_CXX03_LANG
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(initializer_list<_CharT> __il) {
-    __init(__il.begin(), __il.end());
-  }
-
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string(initializer_list<_CharT> __il, const _Allocator& __a)
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
+  basic_string(initializer_list<_CharT> __il, const _Allocator& __a = _Allocator())
       : __alloc_(__a) {
     __init(__il.begin(), __il.end());
   }
diff --git a/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp
index 5dd1d6f0b3380..b08fce2b701e2 100644
--- a/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit.pass.cpp
@@ -12,9 +12,6 @@
 // template <class T, class... Args>
 //   constexpr optional<T> make_optional(Args&&... args);
 
-// GCC crashes on this file, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120577
-// XFAIL: gcc-15
-
 #include <cassert>
 #include <memory>
 #include <optional>
diff --git a/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp
index 5ddb229ad9268..80371d6333712 100644
--- a/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.specalg/make_optional_explicit_initializer_list.pass.cpp
@@ -12,9 +12,6 @@
 // template <class T, class U, class... Args>
 //   constexpr optional<T> make_optional(initializer_list<U> il, Args&&... args);
 
-// GCC crashes on this file, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120577
-// XFAIL: gcc-15
-
 #include <cassert>
 #include <memory>
 #include <optional>

``````````

</details>


https://github.com/llvm/llvm-project/pull/169901