c語言中將函數指針作為形參

Prerequisite: An Example of Null pointer in C

先決條件： C中的空指針示例

Any pointer that contains a valid memory address can be made as a NULL pointer by assigning 0.

通過分配0，可以將包含有效內存地址的任何指針設置為NULL指針 。

Example:

例：

Here, firstly ptr is initialized by the address of num, so it is not a NULL pointer, after that, we are assigning 0 to the ptr, and then it will become a NULL pointer.

在這里，首先ptr由num的地址初始化，因此它不是NULL指針，此后，我們為ptr分配0 ，然后它將成為NULL指針。

Program:

程序：

#include <stdio.h>int main(void) {int num = 10;int *ptr = &num;//we can also check with 0 instesd of NULL if(ptr == NULL)printf("ptr: NULL\n");elseprintf("ptr: NOT NULL\n");//assigning 0 ptr = 0;if(ptr == NULL)printf("ptr: NULL\n");elseprintf("ptr: NOT NULL\n");return 0; }

Output

輸出量

ptr: NOT NULL ptr: NULL

翻譯自: https://www.includehelp.com/c-programs/making-a-valid-pointer-as-null-pointer-in-c.aspx

c語言中將函數指針作為形參

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