在C ++中，是"return;".与"return NULL;"相同吗? [英] In C++, is "return;" the same thing as "return NULL;"?

问题描述

我的问题是 return; 与C ++中的 return NULL; 相同吗?

my question is return; the same as return NULL; in C++?

我了解在C ++中，在指针的上下文中， return NULL; 与 return 0; 相同.显然，对于整数，不是这种情况，因为不能添加，减去NULL，等等.并且有人鼓励对指针使用0而不是NULL，因为它更便于移植.我很好奇这是否是另一个等效的情况.

I understand that in C++, return NULL; is the same as return 0; in the context of pointers. Obviously for integers, this is not the case as NULL cannot be added, subtracted, etc. And that it is encouraged by some to use 0 instead of NULL for pointers because it is more convenient for portability. I'm curious if this is another instance where an equivalence occurs.

我怀疑它们是等效的，因为 return; 说的是return'nothing'，而NULL是'nothing'.但是，如果有人可以确认或否认(当然有解释)，我将不胜感激！

I suspect that they are equivalent because return; is saying return 'nothing' and NULL is 'nothing.' However, if someone can either confirm or deny this (with explanation, of course), I would be very grateful!

推荐答案

return; 是否与C ++中的 return NULL; 相同?

is return; the same as return NULL; in C++?

否.

return 用于从没有返回值(即返回类型为 void )的函数中突围".

return is used to "break" out from a function that has no return value, i.e. a return type of void.

return NULL 返回值 NULL ，并且找到的函数的返回类型必须与 NULL 兼容.

return NULL returns the value NULL, and the return type of the function it's found in must be compatible with NULL.

我了解在C ++中，在指针的上下文中， return NULL; 与 return 0; 相同.

排序. NULL 可能不等同于 0 ，但至少会转换为.

Sort of. NULL may not be equivalent to 0, but it will at least convert to something that is.

对于整数，显然不是这种情况，因为无法添加，减去NULL等.

Obviously for integers, this is not the case as NULL cannot be added, subtracted, etc.

您可以对指针执行加减运算.但是，无论如何， NULL 必须具有整数类型(在C ++ 03中为4.10/1和18.1/4)，因此没有意义. NULL 可能是一个扩展为 0 或 0UL 的宏.

You can perform addition and subtraction to pointers just fine. However, NULL must have integral type (4.10/1 and 18.1/4 in C++03) anyway so it's moot. NULL may very well be a macro that expands to 0 or 0UL.

但是，某些现代编译器至少会警告您，如果它实际上是您编写的 NULL .

Some modern compilers will at least warn you if it was actually NULL you wrote, though.

并且有人鼓励对指针使用0而不是NULL，因为它对于可移植性更加方便.我很好奇这是否是另一个等效的情况.

And that it is encouraged by some to use 0 instead of NULL for pointers because it is more convenient for portability. I'm curious if this is another instance where an equivalence occurs.

不.我不同意这个建议.尽管我可以看到它的来历，但由于 NULL 的确切定义在不同的实现中有所不同，因此使用 NULL 可以使它更容易替换为 nullptr ，当您切换到C ++ 11时，并且如果没有其他内容可自我说明.

No. And I disagree with this advice. Though I can see where it's coming from, since NULL's exact definition varies across implementations, using NULL will make it much easier to replace with nullptr when you switch to C++11, and if nothing else is self-documenting.

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