#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <conio.h>
#include <stdlib.h>

typedef struct information
{
    char name[18];
    char phone[50];
}person;

int Input(person people[])
{
    int count = 0;
    char answer = 'n';

    for(;;)
    {
        printf("姓名:");
        gets(people[count].name);
        printf("电话:");
        gets(people[count++].phone);
        printf("还需要输入？(y/n):");
        scanf(" %c",&answer);

        while(getchar() != '\n');
        if(tolower(answer) == 'n')
            break;
    }
    return count;
}

char *zhuanhuan(char *);

int main(void)
{
    person people[18];
    int count = 0;
    char answer[18] ;
    int i = 0;
    char *temp = NULL;
    char *temp2 = NULL;

    count = Input(people);

    for(;;)
    {
      printf("\n\n\n需要查看信息？(打入名字或者All查看全部):");
      gets(answer);

      if(answer[0] == 'n')
          break;

      if(strcmp(temp = zhuanhuan(answer), "all") == 0)
      {
          free(temp);
          printf("\nAll the information:");
          for(i=0;i<count;i++)
              printf("\nname:%s\nphone:%s\n\n",people[i].name,people[i].phone);
           break;
      }
      else
        {
            printf("\nt = %s\n",temp);
            free(temp);/* 释放没有释放的temp */
            temp = NULL;
            printf("运行");
        for(i=0;i<count;i++)
        {
          if(strcmp(temp = zhuanhuan(answer), temp2 = zhuanhuan(people[i].name)) == 0)
          {
              printf("\nPersonal information:\nname:%s\nphone:%s\n",people[i].name,people[i].phone);
              free(temp);
              free(temp2);
              break;
          }
          free(temp);
          free(temp2);
        }
       }
    }
    return 0;
}

char *zhuanhuan(char *temp)
{
    char *ptemp = (char*)malloc(sizeof temp);
    int i = 0;

    strcpy(ptemp,temp);
   
    for(i=0;i<(int)strlen(ptemp);i++)
    ptemp[i] = tolower(ptemp[i]);

    printf("p = %s\nt = %s\n",ptemp,temp);
    return ptemp;
}

在这里一旦输出的名字多于4个字符如"jdaa"（包括终止符）我的电脑就会出警告

但全部忽略一样可以正常运行，而且是释放temp的空间是出的警告，可在那之前专门检测过temp，里面有数据啊...只希望各位仁兄们把源代码复制一下，运行下看是不是和我一样的结果

sizeof(temp)计算的是一个指针的字节，为4，我懂了谢谢
strlen(temp)+1，只能用这个表达式申请它的空间了吗？还有没有其他办法？

temp是个指针变量，strlen(temp)是根据字符的多少作为返回值的，加上终止符1，对的...