зеркало из https://github.com/microsoft/STL.git
Lifetime cleanups for `basic_string` (#4047)
Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>
This commit is contained in:
achabense
GitHub
Родитель
a9123e8383
Коммит
8d6922ae46
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@ -2287,6 +2287,19 @@ public:
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value_type _Buf[_BUF_SIZE];
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pointer _Ptr;
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char _Alias[_BUF_SIZE]; // TRANSITION, ABI: _Alias is preserved for binary compatibility (especially /clr)
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_CONSTEXPR20 void _Switch_to_buf() noexcept {
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_STD _Destroy_in_place(_Ptr);
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#if _HAS_CXX20
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// start the lifetime of the array elements
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if (_STD is_constant_evaluated()) {
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for (size_type _Idx = 0; _Idx < _BUF_SIZE; ++_Idx) {
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_Buf[_Idx] = value_type();
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}
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}
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#endif // _HAS_CXX20
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}
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};
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_Bxty _Bx;
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@ -2484,13 +2497,11 @@ private:
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public:
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_CONSTEXPR20
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basic_string() noexcept(is_nothrow_default_constructible_v<_Alty>) : _Mypair(_Zero_then_variadic_args_t{}) {
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_Mypair._Myval2._Alloc_proxy(_GET_PROXY_ALLOCATOR(_Alty, _Getal()));
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_Tidy_init();
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_Construct_empty();
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}
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_CONSTEXPR20 explicit basic_string(const _Alloc& _Al) noexcept : _Mypair(_One_then_variadic_args_t{}, _Al) {
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_Mypair._Myval2._Alloc_proxy(_GET_PROXY_ALLOCATOR(_Alty, _Getal()));
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_Tidy_init();
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_Construct_empty();
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}
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_CONSTEXPR20 basic_string(const basic_string& _Right)
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@ -2578,8 +2589,7 @@ public:
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auto _UFirst = _Get_unwrapped(_First);
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auto _ULast = _Get_unwrapped(_Last);
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if (_UFirst == _ULast) {
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_Mypair._Myval2._Alloc_proxy(_GET_PROXY_ALLOCATOR(_Alty, _Getal()));
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_Tidy_init();
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_Construct_empty();
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} else {
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if constexpr (_Is_elem_cptr<decltype(_UFirst)>::value) {
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_Construct<_Construct_strategy::_From_ptr>(
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@ -2630,6 +2640,19 @@ private:
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_Al.deallocate(_Old_ptr, _Capacity + 1); // +1 for null terminator
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}
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_CONSTEXPR20 void _Construct_empty() {
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auto& _My_data = _Mypair._Myval2;
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_My_data._Alloc_proxy(_GET_PROXY_ALLOCATOR(_Alty, _Getal()));
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// initialize basic_string data members
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_My_data._Mysize = 0;
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_My_data._Myres = _Small_string_capacity;
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_My_data._Activate_SSO_buffer();
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// the _Traits::assign is last so the codegen doesn't think the char write can alias this
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_Traits::assign(_My_data._Bx._Buf[0], _Elem());
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}
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enum class _Construct_strategy : uint8_t { _From_char, _From_ptr, _From_string };
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template <_Construct_strategy _Strat, class _Char_or_ptr>
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@ -2918,8 +2941,7 @@ public:
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basic_string(_String_constructor_rvalue_allocator_tag, _Alloc&& _Al)
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: _Mypair(_One_then_variadic_args_t{}, _STD move(_Al)) {
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// Used exclusively by basic_stringbuf
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_Mypair._Myval2._Alloc_proxy(_GET_PROXY_ALLOCATOR(_Alty, _Getal()));
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_Tidy_init();
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_Construct_empty();
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}
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_NODISCARD bool _Move_assign_from_buffer(
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@ -2958,10 +2980,13 @@ public:
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_Released_buffer _Result;
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auto& _My_data = _Mypair._Myval2;
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_Result._Size = _My_data._Mysize;
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_My_data._Orphan_all();
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_ASAN_STRING_REMOVE(*this);
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if (_My_data._Large_mode_engaged()) {
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_Result._Ptr = _My_data._Bx._Ptr;
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_Result._Actual_allocation_size = _My_data._Myres + 1;
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_My_data._Bx._Switch_to_buf();
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} else {
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// use _Least_allocation_size to avoid small mode, if the buffer is assigned back
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size_type _Allocated = _Least_allocation_size;
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@ -2969,8 +2994,9 @@ public:
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_Traits::copy(_Unfancy(_Result._Ptr), _My_data._Bx._Buf, _BUF_SIZE);
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_Result._Actual_allocation_size = _Allocated;
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}
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_My_data._Orphan_all();
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_Tidy_init();
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_My_data._Mysize = 0;
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_My_data._Myres = _Small_string_capacity;
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_Traits::assign(_My_data._Bx._Buf[0], _Elem());
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return _Result;
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}
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#endif // _HAS_CXX20
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@ -3038,27 +3064,34 @@ private:
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const auto _Right_data_mem =
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reinterpret_cast<const unsigned char*>(_STD addressof(_Right._Mypair._Myval2)) + _Memcpy_val_offset;
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_CSTD memcpy(_My_data_mem, _Right_data_mem, _Memcpy_val_size);
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_Right._Tidy_init();
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_Right_data._Mysize = 0;
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_Right_data._Myres = _Small_string_capacity;
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_Right_data._Activate_SSO_buffer();
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_Traits::assign(_Right_data._Bx._Buf[0], _Elem());
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return;
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}
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}
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#endif // !defined(_INSERT_STRING_ANNOTATION)
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if (_Right_data._Large_mode_engaged()) { // steal buffer
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_Construct_in_place(_My_data._Bx._Ptr, _Right_data._Bx._Ptr);
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_Swap_proxy_and_iterators(_Right);
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_Destroy_in_place(_Right_data._Bx._Ptr);
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_Construct_in_place(_My_data._Bx._Ptr, _Right_data._Bx._Ptr);
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_Right_data._Bx._Switch_to_buf();
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} else { // copy small string buffer
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_Right_data._Orphan_all();
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_My_data._Activate_SSO_buffer();
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_Traits::copy(_My_data._Bx._Buf, _Right_data._Bx._Buf, _Right_data._Mysize + 1);
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_Right_data._Orphan_all();
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}
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_My_data._Myres = _Right_data._Myres;
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_My_data._Mysize = _Right_data._Mysize;
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_Right._Tidy_init();
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_Right_data._Mysize = 0;
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_Right_data._Myres = _Small_string_capacity;
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_Traits::assign(_Right_data._Bx._Buf[0], _Elem());
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}
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#if _HAS_CXX23
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@ -4252,9 +4285,7 @@ public:
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static _CONSTEXPR20 void _Swap_bx_large_with_small(_Scary_val& _Starts_large, _Scary_val& _Starts_small) noexcept {
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// exchange a string in large mode with one in small mode
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const pointer _Ptr = _Starts_large._Bx._Ptr;
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_Destroy_in_place(_Starts_large._Bx._Ptr);
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_Starts_large._Activate_SSO_buffer();
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_Starts_large._Bx._Switch_to_buf();
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_Traits::copy(_Starts_large._Bx._Buf, _Starts_small._Bx._Buf, _BUF_SIZE);
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_Construct_in_place(_Starts_small._Bx._Ptr, _Ptr);
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@ -4802,10 +4833,9 @@ private:
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_My_data._Orphan_all();
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_ASAN_STRING_REMOVE(*this);
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const pointer _Ptr = _My_data._Bx._Ptr;
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auto& _Al = _Getal();
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_Destroy_in_place(_My_data._Bx._Ptr);
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_My_data._Activate_SSO_buffer();
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_My_data._Bx._Switch_to_buf();
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_Traits::copy(_My_data._Bx._Buf, _Unfancy(_Ptr), _My_data._Mysize + 1);
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auto& _Al = _Getal();
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_Deallocate_for_capacity(_Al, _Ptr, _My_data._Myres);
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_My_data._Myres = _Small_string_capacity;
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}
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@ -4815,27 +4845,14 @@ private:
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_Traits::assign(_Mypair._Myval2._Myptr()[_Mypair._Myval2._Mysize = _New_size], _Elem());
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}
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_CONSTEXPR20 void _Tidy_init() noexcept {
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// initialize basic_string data members
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auto& _My_data = _Mypair._Myval2;
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_My_data._Mysize = 0;
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_My_data._Myres = _Small_string_capacity;
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_My_data._Activate_SSO_buffer();
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// the _Traits::assign is last so the codegen doesn't think the char write can alias this
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_Traits::assign(_My_data._Bx._Buf[0], _Elem());
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}
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_CONSTEXPR20 void _Tidy_deallocate() noexcept { // initialize buffer, deallocating any storage
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auto& _My_data = _Mypair._Myval2;
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_My_data._Orphan_all();
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if (_My_data._Large_mode_engaged()) {
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_ASAN_STRING_REMOVE(*this);
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const pointer _Ptr = _My_data._Bx._Ptr;
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auto& _Al = _Getal();
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_Destroy_in_place(_My_data._Bx._Ptr);
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_My_data._Activate_SSO_buffer();
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_Deallocate_for_capacity(_Al, _Ptr, _My_data._Myres);
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auto& _Al = _Getal();
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_Deallocate_for_capacity(_Al, _My_data._Bx._Ptr, _My_data._Myres);
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_My_data._Bx._Switch_to_buf();
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}
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_My_data._Mysize = 0;
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@ -3,6 +3,7 @@
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#include <algorithm>
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#include <cassert>
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#include <crtdbg.h>
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#include <cstdlib>
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#include <cstring>
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#include <deque>
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@ -15,6 +16,7 @@
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#include <memory>
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#include <new>
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#include <set>
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#include <sstream>
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#include <string>
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#include <type_traits>
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#include <unordered_map>
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@ -971,6 +973,20 @@ _CONSTEXPR20 void test_string_swap(const size_t id1, const size_t id2) {
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assert(dst.get_allocator().id() == id1);
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}
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#if _HAS_CXX20
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void test_string_move_to_stringbuf() {
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// GH-4047 fixed a bug where basic_string forgets to destroy the pointer before switching to small
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// mode. This will turn problematic if the pointer is non-trivial.
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assert(!_CrtDumpMemoryLeaks());
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{
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using Alloc = StationaryAlloc<char>;
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basic_string<char, char_traits<char>, Alloc> str(50, '0', Alloc(10));
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basic_stringbuf<char, char_traits<char>, Alloc> strbuf(move(str));
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}
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assert(!_CrtDumpMemoryLeaks());
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}
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#endif // _HAS_CXX20
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_CONSTEXPR20 bool test_string() {
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test_string_copy_ctor();
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@ -1002,6 +1018,11 @@ _CONSTEXPR20 bool test_string() {
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test_string_swap<SwapAlloc<char32_t>>(11, 22); // POCS, non-equal allocators
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test_string_swap<SwapEqualAlloc<char32_t>>(11, 22); // POCS, always-equal allocators
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#if _HAS_CXX20
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if (!is_constant_evaluated()) {
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test_string_move_to_stringbuf();
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}
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#endif // _HAS_CXX20
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return true;
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}
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