c++ - std::malloc 可以创建一个对象吗？总是需要安置新的吗？-6ren

c++ - std::malloc 可以创建一个对象吗？总是需要安置新的吗？

转载作者：太空宇宙更新时间：2023-11-04 14:33:17

<分区>

这段代码在 C++ 中是否有未定义的行为？

#include <cstdlib>

int main() {
    int *ip = static_cast<int *>(std::malloc(sizeof *ip));
    *ip = 42; //is this accessing an object that has not started its lifetime?
    free(ip);
}

注意事项:
std::malloc has the semantics that it has in C .在 C 中，std::malloc 创建有效的 int，所以它应该是有效的？

The lifetime of an object or reference is a runtime property of the object or reference. An object is said to have non-vacuous initialization if it is of a class or aggregate type and it or one of its subobjects is initialized by a constructor other than a trivial default constructor. [ Note: Initialization by a trivial copy/move constructor is non-vacuous initialization. — end note ] The lifetime of an object of type T begins when:

(1.1) storage with the proper alignment and size for type T is obtained, and
(1.2) if the object has non-vacuous initialization, its initialization is complete,

except that if the object is a union member or subobject thereof ...

source

我相当确定这句话回答了我的问题，但我对它的理解还不够好，无法判断它是说是还是不是。