blocks|key|704399|text|§5.3.5/2“在第一种选择(delete对象)中，delete操作数的值可以是空指针值，指向由先前new表达式创建的非数组对象的指针，或指向表示此类对象基类的子对象(1.8)的指针(第10条)。如果不是，则行为未定义。”因为bar指向一个double，所以它不指向由前一个new-expression+(创建了一个int)创建的对象。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|704400|entityMap^0|36|3|3D|6|4F|3|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

§5.3.5/2 "In the first alternative (delete object), the value of
the operand of delete may be a null pointer value, a pointer to
a non-array object created by a previous new-expression, or
a pointer to a subobject (1.8) representing a base class of such
an object (Clause 10). If not, the behavior is undefined." Since
<code>bar</code> points to a <code>double</code>, it does not point to an object
created by a previous new-expression (which created an <code>int</code>).

blocks|key|2045809|text|您的位置如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2045810|2045811|+5.3.5第3点:在第一种选择(删除对象)中，如果要删除的对象的静态类型与其动态类型不同，则静态类型必须是要删除的对象的动态类型的基类，并且静态类型必须有一个虚析构函数或行为未定义。|blockquote|2045812|2045813|2045814|至于什么是静态类型和动态类型的问题：|2045815|2045816|+1.3.7动态类型(GL值)|2045817|2045818|由glvalue表达式表示的glvalue引用的最派生对象(1.8)的类型示例:如果静态类型为“指向类B的指针”的指针(8.3.1)+p指向从B派生的类D的对象(第10条)，则表达式*p的动态类型为“D”。引用(8.3.2)的处理方式与此类似。-end示例|2045819|1.3.23静态类型|2045820|表达式的类型(3.9)是通过分析程序而不考虑执行语义得到的注意:表达式的静态类型仅取决于出现表达式的程序的形式，并且在程序执行时不会改变。-end笔记|2045821|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|W|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|X|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|10|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|E|7|12|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|14|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|15|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|16|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|U|$]]

Here you are:

<blockquote>
 5.3.5 point 3: In the first alternative (delete object), if the static type of the object to be deleted is different from its
 dynamic type, the static type shall be a base class of the dynamic type of the object to be deleted and the
 static type shall have a virtual destructor or the behavior is undefined.
</blockquote>

As for questions of what is static and dynamic type:

<blockquote>
 1.3.7 dynamic type (glvalue) 
 type of the most derived object (1.8) to which the glvalue denoted by a glvalue expression refers
 [ Example: if a pointer (8.3.1) p whose static type is “pointer to class B” is pointing to an object of class
 D, derived from B (Clause 10), the dynamic type of the expression *p is “D.” References (8.3.2) are treated
 similarly. —end example ]
 
 1.3.23 static type 
 type of an expression (3.9) resulting from analysis of the program without considering execution semantics
 [Note: The static type of an expression depends only on the form of the program in which the expression
 appears, and does not change while the program is executing. —end note]
</blockquote>

blocks|key|1846124|text|从5.3.5到3：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1846125|1846126|在第一种选择(删除对象)中，如果要删除的对象的静态类型与其动态类型不同，则静态类型应为要删除的对象的动态类型的基类，并且静态类型应具有虚拟析构函数或行为未定义。|blockquote|1846127|1846128|1846129|抛开在这里使用reinterpret_cast时可能出现的问题不谈，这是UB，因为类型不匹配。想象一下一些非平凡的类型，那么您可以很容易地看到这一点，因为“错误的”dtor将被调用。|offset|length|style|CODE|1846130|此外，将reinterpret_cast的结果用于任何其他用途，而不是将其转换回来，这在标准中基本上是未指定的。|1846131|entityMap^0|0|0|0|0|0|7|G|0|4|G|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|S|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|T|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@$J|X|K|Y|L|M]]|9|@]|A|$]]|$1|N|3|O|5|6|7|Z|8|@$J|10|K|11|L|M]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|Q|$]]

From 5.3.5-3:

<blockquote>
 In the first alternative (delete object), if the static type of the
 object to be deleted is different from its dynamic type, the static
 type shall be a base class of the dynamic type of the object to be
 deleted and the static type shall have a virtual destructor or the
 behavior is undefined.
</blockquote>

Leaving aside possible problems in using <code>reinterpret_cast</code> here, this is UB because the types do not match. Imagine some nontrivial type, then you can easily see this as the "wrong" dtor would be called.

Additionally using the result of <code>reinterpret_cast</code> for anything else than casting it back is mostly unspecified by the standard.

Can i use smth like the following code:

<pre><code>int main()
{
 int* foo = new int;
 double* bar = reinterpret_cast&lt;double*&gt;(foo);
 delete bar;
}
</code></pre>

Is it UB?

I think that we need to call operator delete only for pointers returned by operator new, but what about casting in this case?

I think that it's UB since the reinterpret_cast don't give any guarantees about the resulting pointer. Am i right?

Can somebody post the right quote from the standard, please?

Operator delete and casting

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我可以像下面的代码一样使用smth吗：int main(){ int* foo = new int; double* bar = reinterpret_cast<double*>(foo); delete bar;}是UB吗？我认为我们只需要为new返回的指针调用delete操作符，但在这种情况下强...

问运算符delete和转换
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问运算符delete和转换EN