test.c:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
 
// return赋值
char **char_set_v0(int *n)
{
    char **p = (char **)malloc(3 * sizeof(char *));
    if (p == NULL) {
        printf("out of mem\n");
        return NULL;
    }
    int i =0;
    for (i=0; i<3; i++) {
        *(p+i) = (char *)malloc(1024);
        if (*(p+i) == NULL) {
            printf("out of mem\n");
            return NULL;
        }
        snprintf(*(p+i), 1023, "hello %d", i+1);
    }
    *n = 3;
     
    return p;
}
 
// 参数赋值
int char_set_v1(char ***m)
{
    char **p = (char **)malloc(3 * sizeof(char *));
    if (p == NULL) {
        printf("out of mem\n");
        return 0;
    }
    int i = 0;
    for (i=0; i<3; i++) {
        p[i] = (char *)malloc(1024);
        if (p[i] == NULL) {
            printf("out of mem\n");
            return 0;
        }
        snprintf(p[i], 1023, "hello %d", i+1);
    }
    *m = p;
    return i;
}
 
 
int main(int argc, char **argv)
{
    int i = 0;
    int ret = 0;
    printf(" ---- 0 ------\n");
    char **p = NULL;
    p = char_set_v0(&ret);
    if (p != NULL) {
        for(i=0; i<ret; i++) {
            printf("[%d] %s\n", i, *(p+i));
        }
        for(i=0; i<ret; i++) {
            if (*(p+i) != NULL) {
                free(*(p+i));
                *(p+i) = NULL;
            }
        }
        free(p);
        p = NULL;
    }
     
    printf(" ---- 1 ------\n");
    char **m = NULL;
    ret = char_set_v1(&m);
    if (m != NULL) {
        for(i=0; i<ret; i++) {
            printf("[%d] %s\n", i, m[i]);
        }
        for(i=0; i<ret; i++) {
            if (m[i] != NULL) {
                free(m[i]);
                m[i] = NULL;
            }
        }
        free(m);
        m = NULL;
    }
    return 1;
}

编译&执行:

gcc -g -o test test.c
./test