求一笔试题的输出结果！

bjutslg

int main()
{
        char **p=new char*[100];
        int ret;
        int i;
        for(i=0;i<sizeof(p);i++)
        {
           p[i]=new char[i];
           ret =i;
        }
        delete []p;
        p=NULL;
    cout<<ret<<endl;
        return 0;
}

一个笔试题，有四个选项：一个是程序有时会出错，一个是程序崩溃，一个是ret=99，还有一个忘了，但是貌似给的选项没有3？

hellioncu

这题不严谨，32位、64位结果不一样。再说万一new 失败了抛异常，程序会崩溃。

bjutslg

32为下，如果new不出错的话，是不是就应该是ret=3了，再有p=new char[]这是什么意思啊？？回复 2# hellioncu


   

hellioncu

bjutslg 发表于 2014-05-25 19:52
32为下，如果new不出错的话，是不是就应该是ret=3了，再有p=new char[]这是什么意思啊？？回复 2# hellionc ...

那应该是3。

申请一个char数组

folklore

memory leak...

bjutslg

怎么讲??回复 5# folklore


   

bjutslg

讲清楚点呗，哪里会引起内存泄露啊？回复 5# folklore


   

Herowinter

p [ i ]=new char [ i ];这句，你没有释放p [ i ] 的内存。
回复 7# bjutslg

1. valgrind --tool=memcheck --leak-check=full --show-reachable=yes --track-origins=yes ./t
   
2. ==7408== Memcheck, a memory error detector
   
3. ==7408== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
   
4. ==7408== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
   
5. ==7408== Command: ./t
   
6. ==7408==
   
7. 7
   
8. ==7408==
   
9. ==7408== HEAP SUMMARY:
   
10. ==7408==     in use at exit: 28 bytes in 8 blocks
    
11. ==7408==   total heap usage: 9 allocs, 1 frees, 828 bytes allocated
    
12. ==7408==
    
13. ==7408== 28 bytes in 8 blocks are definitely lost in loss record 1 of 1
    
14. ==7408==    at 0x4A07152: operator new[](unsigned long) (vg_replace_malloc.c:363)
    
15. ==7408==    by 0x4008B0: main (test.cpp:10)
    
16. ==7408==
    
17. ==7408== LEAK SUMMARY:
    
18. ==7408==    definitely lost: 28 bytes in 8 blocks
    
19. ==7408==    indirectly lost: 0 bytes in 0 blocks
    
20. ==7408==      possibly lost: 0 bytes in 0 blocks
    
21. ==7408==    still reachable: 0 bytes in 0 blocks
    
22. ==7408==         suppressed: 0 bytes in 0 blocks
    
23. ==7408==
    
24. ==7408== For counts of detected and suppressed errors, rerun with: -v
    
25. ==7408== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 6 from 6)

复制代码

bjutslg

还真是啊 没有注意到for循环中的new！你下面这些代码是什么意思啊 没见过哎回复 8# Herowinter


   

Herowinter

回复 9# bjutslg
一个测试程序内存问题的工具valgrind，有兴趣可以google下，
做C/C++开发，基本都用得上。