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| Member functions | ||||
(until C++20) | ||||
(C++23) | ||||
allocator::deallocate | ||||
(until C++20) | ||||
(until C++20) | ||||
(until C++20) | ||||
| Non-member functions | ||||
(until C++20) |
void deallocate( T* p,std::size_t n); | (constexpr since C++20) | |
Deallocates the storage referenced by the pointerp, which must be a pointer obtained by an earlier call toallocate() orallocate_at_least()(since C++23).
The argumentn must be equal to the first argument of the call toallocate() that originally producedp, or in the range[m, count] ifp is obtained from a call toallocate_at_least(m) which returned{p, count}(since C++23); otherwise, the behavior is undefined.
Calls::operator delete(void*)or::operator delete(void*,std::align_val_t)(since C++17), but it is unspecified when and how it is called.
In evaluation of a constant expression, this function must deallocate storage allocated within the evaluation of the same expression. | (since C++20) |
Contents |
| p | - | pointer obtained fromallocate() orallocate_at_least()(since C++23) |
| n | - | number of objects earlier passed toallocate(), or a number between requested and actually allocated number of objects viaallocate_at_least() (may be equal to either bound)(since C++23) |
(none)
#include <algorithm>#include <cstddef>#include <iostream>#include <memory>#include <string> class S{inlinestaticint n{1};int m{};void pre()const{std::cout<<"#"<< m<<std::string(m,' ');}public: S(int x): m{n++}{ pre();std::cout<<"S::S("<< x<<");\n";} ~S(){ pre();std::cout<<"S::~S();\n";}void id()const{ pre();std::cout<<"S::id();\n";}}; int main(){constexprstd::size_t n{4};std::allocator<S> allocator;try{ S* s= allocator.allocate(n);// may throwfor(std::size_t i{}; i!= n;++i){// allocator.construct(&s[i], i + 42); // removed in C++20std::construct_at(&s[i], i+42);// since C++20}std::for_each_n(s, n,[](constauto& e){ e.id();});std::destroy_n(s, n); allocator.deallocate(s, n);}catch(std::bad_array_new_lengthconst& ex){std::cout<< ex.what()<<'\n';}catch(std::bad_allocconst& ex){std::cout<< ex.what()<<'\n';}}
Output:
#1 S::S(42);#2 S::S(43);#3 S::S(44);#4 S::S(45);#1 S::id();#2 S::id();#3 S::id();#4 S::id();#1 S::~S();#2 S::~S();#3 S::~S();#4 S::~S();
| allocates uninitialized storage (public member function)[edit] | |
(C++23) | allocates uninitialized storage at least as large as requested size (public member function)[edit] |
[static] | deallocates storage using the allocator (public static member function of std::allocator_traits<Alloc>)[edit] |
