C 语言指针的用法

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1.指针基本介绍

#include <stdio.h>#include <stdlib.h>#include <stdint.h>int main() {    int a = 10;    int *pa = &a;    printf("%d\n", *pa);    int32_t *intP = (int32_t *) malloc(4);    *intP = 100;    printf("%d\n", *intP);    int32_t *intPo = (int32_t *) malloc(4);    intPo[0] = 101;    printf("%d\n", *intPo);    int len = 10;    int32_t *intPoi = (int32_t *) malloc(len * sizeof(int32_t));    intPoi[0] = 102;    intPoi[1] = 103;    printf("%d\n", intPoi[1]);    printf("%d\n", *(intPoi + 1));    free(intPoi);    char *str = "Hello";    printf("%ld\n", sizeof(str));//指针长度 64位 8  32位 4    int64_t poin = (int64_t) str;//int64_t和指针相互转换  JNI(Java Native Interface) Java long==C int64_t    char *str1 = (char *) poin;    printf("%s\n", str1);    return 0;}

2.函数指针

#include <stdio.h>void hello(){    printf("Hello World!\n");}//自定义typedef void (*SimpleFunc)();int main() {    //常规方式    hello();    //函数指针    void (*fp)() = &hello;    fp();    //自定义    SimpleFunc simpleFunc = &hello;    simpleFunc();    return 0;}

3.无类型指针

#include <stdio.h>#include <stdlib.h>int main() {    //无类型指针    void *data = "Hello C";    printf("%s\n", data);    void *a = malloc(8);    printf("%ld\n", sizeof(a[0]));//无类型指针的访问单元  1字节    void *b = malloc(8);    int *intb = b;    printf("%ld\n", sizeof(intb[0]));//指定类型后 变成4字节    intb[0] = 10000;    printf("%d\n", intb[0]);    free(b);    void *c = 10000;    printf("%d\n", c);    return 0;}

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