问题虽简单但值得问透彻了解

sybaselu

1. 
   
2. #include <stdlib.h>
   
3. #include <stdio.h>
   
4. #include <string.h>
   
5. 
   
6. int main(void)
   
7. {
   
8.     char* iconfilename[20];
   
9.     char* iconfile = " I very very love motherland";
   
10.   
    
11.     memcpy(iconfilename, iconfile, strlen(iconfile)+1);
    
12.     fprintf(stdout, "%s\n", iconfilename);
    
13. 
    
14.     strncpy(iconfilename, iconfile, 20);
    
15.     fprintf(stdout, "%s\n", iconfilename);
    
16. 
    
17.     strcpy(iconfilename, iconfile);
    
18.     fprintf(stdout, "%s\n", iconfilename);
    
19. 
    
20.    
    
21.     return 0;
    

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这几种的拷贝那个比较安全，那个危险，为什么？

ideawu

这三种方法都是不安全的。
第一种可能导致Segmentation fault
第二种iconfilename字符串因为可能没有'\0'结束符，用fprintf输出时导致输出的内容比iconfilename[]数组存储的内容还要多。
第三种可能导致Segmentation fault

zhllg

第二个，拷贝完把[20]赋值为'\0'就没事了

sybaselu

如果这样的都安全了吧

1. 
   
2. char iconfile[] = " I very very love motherland";
   
3. 
   

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strcpy的des要足够大，否则内存溢出？

zhllg

你试试能编译通过么

ideawu

Post by zhllg
第二个，拷贝完把[20]赋值为'\0'就没事了

呵呵，应该是[19].

Post by sybaselu
如果这样的都安全了吧

1. 
   
2. char* iconfile[] = " I very very love motherland";
   

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char* iconfile = " I very very love motherland";这条语句是安全的。只是下面的拷贝语句不安全。

sybaselu

1. 
   
2. int main(void)
   
3. {
   
4.     char iconfilename[20];
   
5.     char* iconfile = "I very very love aaahaa";
   
6. 
   
7.     memcpy(iconfilename, iconfile, 10);
   
8.     printf("%s\n", iconfilename);
   
9. 
   
10. 
    
11.     strncpy(iconfilename, iconfile, 10);
    
12.     printf("%s\n", iconfilename);
    
13. 
    
14.     return 0;
    
15. }
    
16. [root@root GUI]# gcc PointerIni.c -o PointerIni -Wall
    
17. [root@root GUI]# ./PointerIni
    
18. I very ver泾j
    
19. 
    
20. I very ver泾j
    
21. [root@root GUI]# vi PointerIni.c
    
22. ...
    
23. int main(void)
    
24. {
    
25.     char iconfilename[20];
    
26.     char* iconfile = "I very very love aaahaa";
    
27. 
    
28.     memcpy(iconfilename, iconfile, 10);
    
29.     fprintf(stdout, "%s\n", iconfilename);
    
30. 
    
31. 
    
32.     strncpy(iconfilename, iconfile, 10);
    
33.     fprintf(stdout, "%s\n", iconfilename);
    
34. 
    
35.     return 0;
    
36. }
    
37. "PointerIni.c" 20L, 345C written                              
    
38. [root@root GUI]# gcc PointerIni.c -o PointerIni -Wall
    
39. [root@root GUI]# ./PointerIni
    
40. I very ver帼
    
41. 
    
42. I very ver帼
    
43. 
    
44. [root@root GUI]#
    
45. 
    

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对memcpy()来说，拷贝字符串时多少个字节和多少个character没有区别，但memcpy()用来拷贝非char时，就要注意num of bytes

zhllg

Post by ideawu
呵呵，应该是[19].

笔误，了解我的意思就好了，呵呵
反正就是加个'\0'作为结束

Post by ideawu

char* iconfile = " I very very love motherland";这条语句是安全的。只是下面的拷贝语句不安全。

但是
char* iconfile[] = " I very very love motherland";
是错的

zhllg

2. #include<stdio.h>
3. #include<string.h>
4. int main(void)
5. {
6.     char iconfilename[20];
7.     char* iconfile = "I very very love aaahaa";
9.     memcpy(iconfilename, iconfile, 10);
10.     iconfilename[9] = '\0';
11.     fprintf(stdout, "%s\n", iconfilename);
14.     strncpy(iconfilename, iconfile, 10);
15.     iconfilename[9] = '\0';
16.     fprintf(stdout, "%s\n", iconfilename);
18.     return 0;
19. }

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