c_cpp: 指针的双重赋值

c/cpp: 指针的双重赋值

一、指针使用、引用的运用

　　1、指针具有双重赋值的属性：第一重赋值，为指针变量赋值内存地址；第二重赋值，为指针变量所指的内存的存储空间赋予内容。

二、代码部分

　　1、c代码

 1 [root@rockylinux tmp]# uname -a
 2 Linux rockylinux 4.18.0-372.19.1.el8_6.x86_64 #1 SMP Tue Aug 2 16:19:42 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
 3 [root@rockylinux tmp]# 
 4 [root@rockylinux tmp]# 
 5 [root@rockylinux tmp]# gcc --version
 6 gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-10)
 7 Copyright (C) 2018 Free Software Foundation, Inc.
 8 This is free software; see the source for copying conditions.  There is NO
 9 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
10 
11 [root@rockylinux tmp]# 
12 [root@rockylinux tmp]# 
13 [root@rockylinux tmp]# cat pointer_double.c
14 #include<stdio.h>
15 #include<stdlib.h>
16 
17 
18 void msg()
19 {
20 
21         int para = 30;
22 
23 
24         // 指针第一重赋值
25         int* pointer_int = &para;
26 
27 
28         printf("FIRST:\t para_address=%p, pointer_int=%p\n", &para, pointer_int);
29         printf("FIRST:\t para_value=%d, *pointer_int=%d\n", para, *pointer_int);
30 
31 
32         // 指针的第二重赋值
33         *pointer_int=60;
34 
35         printf("SECOND:\t para_address=%p, pointer_int=%p\n", &para, pointer_int);
36         printf("SECOND:\t para_value=%d, *pointer_int=%d\n", para, *pointer_int);
37 
38 }
39 
40 
41 int main(int argc, char* argv[], char* envp[])
42 {
43         msg();
44 
45         return 0;
46 }
47 [root@rockylinux tmp]# 
48 [root@rockylinux tmp]# 
49 [root@rockylinux tmp]# gcc -o pointer_double_c pointer_double.c
50 [root@rockylinux tmp]# 
51 [root@rockylinux tmp]# 
52 [root@rockylinux tmp]# ./pointer_double_c
53 FIRST:   para_address=0x7ffd3636d594, pointer_int=0x7ffd3636d594
54 FIRST:   para_value=30, *pointer_int=30
55 SECOND:  para_address=0x7ffd3636d594, pointer_int=0x7ffd3636d594
56 SECOND:  para_value=60, *pointer_int=60
57 [root@rockylinux tmp]# 
58 [root@rockylinux tmp]#

　　2、cpp代码

 1 [root@rockylinux tmp]# uname -a
 2 Linux rockylinux 4.18.0-372.19.1.el8_6.x86_64 #1 SMP Tue Aug 2 16:19:42 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
 3 [root@rockylinux tmp]# 
 4 [root@rockylinux tmp]# 
 5 [root@rockylinux tmp]# g++ --version
 6 g++ (GCC) 8.5.0 20210514 (Red Hat 8.5.0-10)
 7 Copyright (C) 2018 Free Software Foundation, Inc.
 8 This is free software; see the source for copying conditions.  There is NO
 9 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
10 
11 [root@rockylinux tmp]# 
12 [root@rockylinux tmp]# 
13 [root@rockylinux tmp]# cat  pointer_double.cpp
14 #include<iostream>
15 
16 
17 using namespace std;
18 
19 
20 void msg()
21 {
22 
23         int para = 30;
24 
25 
26         // 指针第一重赋值
27         int* pointer_int = &para;
28 
29         cout <<"FIRST:\tpara_address="<< &para << ", pointer_int=" << pointer_int << endl;
30         cout <<"FIRST:\tpara_value="<< para << ", *pointer_int=" << *pointer_int << endl;
31 
32 
33         // 指针的第二重赋值
34         *pointer_int=60;
35 
36         cout <<"SECOND:\tpara_address="<< &para << ", pointer_int=" << pointer_int << endl;
37         cout <<"SECOND:\tpara_value="<< para << ", *pointer_int=" << *pointer_int << endl;
38 
39 }
40 
41 
42 int main(int argc, char* argv[], char* envp[])
43 {
44         msg();
45 
46         return 0;
47 }
48 [root@rockylinux tmp]# 
49 [root@rockylinux tmp]# 
50 [root@rockylinux tmp]# g++ -o pointer_double_cpp pointer_double.cpp 
51 [root@rockylinux tmp]# 
52 [root@rockylinux tmp]# 
53 [root@rockylinux tmp]# ./pointer_double_cpp
54 FIRST:  para_address=0x7fffab0dfad4, pointer_int=0x7fffab0dfad4
55 FIRST:  para_value=30, *pointer_int=30
56 SECOND: para_address=0x7fffab0dfad4, pointer_int=0x7fffab0dfad4
57 SECOND: para_value=60, *pointer_int=60
58 [root@rockylinux tmp]# 
59 [root@rockylinux tmp]#

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原文地址：https://www.cnblogs.com/lnlidawei/p/16647216.html