：

C ++标准，第5.2.11节/第7节[const cast]

C++ standard, section § 5.2.11/7 [const cast]

[注意：根据对象的类型，通过指向const_cast的指针，值或指针到数据成员的写操作限定符可能会产生未定义的行为。 -end note]

[ Note: Depending on the type of the object, a write operation through the pointer, lvalue or pointer to data member resulting from a const_cast that casts away a const-qualifier may produce undefined behavior. —end note ]

GetA（） code> Bob ，因此此程式不涉及未定义的行为。

GetA() does not write any member of Bob, so this program does not involve undefined behavior.