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- placement new 容许咱们将 object 构建于 allocated memory 中;
- 没有所谓 placement delete,因为 placement new 基本没调配 memory;
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亦或称说与 placement new 对应的 operator delete 为 placement delete。
#include <new> char *buf = new char[sizeof(Complex) * 3]; Complex *pc = new(buf) Complex (1, 2); // ... delete[] buf;
Complex *pc = new(buf) Complex (1, 2);
编译器转换为 ==>
Complex *pc;
try {void* mem = operator new (sizeof(Complex), buf); // allocate
pc = static_cast<Complex*>(mem); // cast
pc->Complex::Complex(1, 2); // construct
}
catch(std::bad_alloc) {// 若 allocation 失败就不执行 constructor}
void* mem = operator new (sizeof(Complex), buf);
源码实现 ==>
void *operator new (size_t, viud *loc)
{return loc;}
正文完