问题描述
通过简单地编写 if(pointer) 来检查指针是否为 NULL 是否安全，或者我是否必须使用 if(pointer != NULL)?
Is it safe to check a pointer to not being NULL by writing simply if(pointer) or do I have to use if(pointer != NULL)?
推荐答案
你可以；空指针被隐式转换为布尔值 false 而非空指针被转换为 true.来自 C++11 标准，关于布尔转换的部分:
You can; the null pointer is implicitly converted into boolean false while non-null pointers are converted into true. From the C++11 standard, section on Boolean Conversions:
算术、无作用域枚举、指针或指向成员类型的指针的纯右值可以转换为类型的纯右值布尔.零值、空指针值或空成员指针值被转换为假;任何其他值都转换为真.类型的纯右值std::nullptr_t可以转换为纯右值类型bool;结果值是假.
A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type
bool. A zero value, null pointer value, or null member pointer value is converted tofalse; any other value is converted totrue. A prvalue of typestd::nullptr_tcan be converted to a prvalue of typebool; the resulting value isfalse.
这篇关于我可以使用 if (pointer) 而不是 if (pointer != NULL) 吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！