As far as i know, the NULL is actually not 0. So is there any difference in comparing a pointer with 0 or with NULL? Further what should be the correct usage. Thanks!
3 回答
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The correct usage is to use NULL : It's more readable (p = NULL -> you know that p is a pointer)
于 2013-07-08T12:52:20.443 回答
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In C,the macro NULL is defined as an implementation-defined null pointer constant, which in C99 can be portably expressed as the integer value 0 converted implicitly or explicitly to the type void*.
In C++ NULL is the integer literal for zero (0 or 0L) has been traditionally preferred to represent a null pointer constant.
Compiler would implicitly convert 0 to NULL in case of comparison with a pointer.
It is always safe to compare 0 with NULL.
于 2013-07-08T12:55:59.413 回答
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NULL is not necessarily 0 and should only be used for pointers. NULL is a macro usually defined as (void*)0 but not always.
It's a pointer to no location in memory.
There's a very good new book called Understanding And Using C Pointers. Please read that one.
Don't use it for anything but pointers.
于 2013-07-08T12:59:12.863 回答