class X { /* ... */}; void* raw = malloc(sizeof (X)); X* p = new (raw) X(); // according to the standard,the RHS is a placement-new expression ::operator delete(p); // definitely wrong,per litb's answer delete p; // legal? I hope not
也许你们中的一位语言律师可以解释这个标准是禁止这个.
还有一个数组形式:
class X { /* ... */}; void* raw = malloc(sizeof (X)); X* p = new (raw) X[1]; // according to the standard,the RHS is a placement-new expression ::operator delete[](p); // definitely wrong,per litb's answer delete [] p; // legal? I hope not
This is the closest question我能找到.
编辑:我只是不认为标准的语言限制参数的函数void :: operator delete(void *)的用法以任何有意义的方式应用于delete-expression中的delete操作数.最好,两者之间的连接是非常脆弱的,并且允许一些表达式作为删除的操作数,这些操作不能传递给void :: operator delete(void *).例如:
struct A { virtual ~A() {} }; struct B1 : virtual A {}; struct B2 : virtual A {}; struct B3 : virtual A {}; struct D : virtual B1,virtual B2,virtual B3 {}; struct E : virtual B3,virtual D {}; int main( void ) { B3* p = new E(); void* raw = malloc(sizeof (D)); B3* p2 = new (raw) D(); ::operator delete(p); // definitely UB delete p; // definitely legal ::operator delete(p2); // definitely UB delete p2; // ??? return 0; }
我希望这可以说明一个指针是否可以被传递给void operator delete(void *)与该指针是否可以用作delete的操作数无关.
解决方法
Otherwise,the value supplied to
operator delete(void*)
in the standard library shall be one of the values returned by a prevIoUs invocation of eitheroperator new(size_t)
oroperator new(size_t,const std::nothrow_t&)
in the standard library,and the value supplied tooperator delete[](void*)
in the standard library shall be one of the values returned by a prevIoUs invocation of eitheroperator new[](size_t)
oroperator new[](size_t,const std::nothrow_t&)
in the standard library.
您的删除呼叫将调用库的运算符delete(void *),除非您已经覆盖.既然你没有说过什么,我会假设你没有.
上面的“应该”应该是像“行为不定义,如果不是”,所以它不被误认为是一个可诊断的规则,它不是由[lib.res.on.arguments] p1.这被n3225纠正了,所以不能再错了.