const char **,char *const *,char ** const

Posted 2022-06-11

1、告警

test_cpp.c

#include <stdlib.h>
#include <stdio.h>

int main()

       char c = ‘c‘;
        char c_q = ‘c‘;

        char *p = &c;
        char *q = &c_q;

        char **pp = &p;
        const char **cpp = &p;
        char const **c_pp = &p;
        char  * const *pcp = &p;
        char  ** const ppc = &p;

        return 0;

编译的时候有如下警告：

x@ubuntu:~/Desktop/const$ gcc text_cpp.c
text_cpp.c: In function ‘main’:
text_cpp.c:13:21: warning: initialization of ‘const char **’ from incompatible pointer type ‘char **’ [-Wincompatible-pointer-types]
  const char **cpp = &p;
                     ^
text_cpp.c:14:22: warning: initialization of ‘const char **’ from incompatible pointer type ‘char **’ [-Wincompatible-pointer-types]
  char const **c_pp = &p;
                      ^

2、错误

#include <stdlib.h>
#include <stdio.h>

int main()

        char *p_str[] = "char **",
                         "const char ** ",
                         "char * const * ",
                         "char ** const ",;

        char **pp = p_str;
        const char **cpp = p_str;
        char  * const *pcp = p_str;
        char  ** const ppc = p_str;

        *pp  = "assign  char **";
        *cpp = "assign  const char **";
        *pcp = "assign  char * const *";
        *ppc = "assign  char ** const";

        return 0;

出现如下编译错误：

x@ubuntu:~/Desktop/const$ gcc text_cpp.c
text_cpp.c: In function ‘main’:
text_cpp.c:12:21: warning: initialization of ‘const char **’ from incompatible pointer type ‘char **’ [-Wincompatible-pointer-types]
  const char **cpp = p_str;
                     ^~~~~
text_cpp.c:18:7: error: assignment of read-only location ‘*pcp’
  *pcp = "assign  char * const *";
       ^