Valgrind检测非法访问内存

谁践踏了优雅 2021-09-19 11:24 360阅读 0赞

**一 代码**

#include<iostream>
    #include<stdlib.h>
    using namespace std;
    void func(){
        int *x=(int *)malloc( 10 * sizeof ( int ) ) ;
        x[10]=0;
    }
    int main(){
        func();
        cout<<"done"<<endl;
        return 0;
    }

**二 编译并运行**

[root@localhost charpter05]# g++ -g 0508test.cpp -o 0508
    [root@localhost charpter05]# ./0508
    done

**三 用Valgrind检测非法访问内存**

[root@localhost charpter05]# valgrind ./0508
    ==16719== Memcheck, a memory error detector
    ==16719== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
    ==16719== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
    ==16719== Command: ./0508
    ==16719==
    ==16719== Invalid write of size 4
    ==16719==    at 0x4008DE: func() (0508test.cpp:6)
    ==16719==    by 0x4008EE: main (0508test.cpp:9)
    ==16719==  Address 0x5a1a068 is 0 bytes after a block of size 40 alloc'd
    ==16719==    at 0x4C29EC3: malloc (vg_replace_malloc.c:309)
    ==16719==    by 0x4008D1: func() (0508test.cpp:5)
    ==16719==    by 0x4008EE: main (0508test.cpp:9)
    ==16719==
    done
    ==16719==
    ==16719== HEAP SUMMARY:
    ==16719==     in use at exit: 40 bytes in 1 blocks
    ==16719==   total heap usage: 1 allocs, 0 frees, 40 bytes allocated
    ==16719==
    ==16719== LEAK SUMMARY:
    ==16719==    definitely lost: 40 bytes in 1 blocks
    ==16719==    indirectly lost: 0 bytes in 0 blocks
    ==16719==      possibly lost: 0 bytes in 0 blocks
    ==16719==    still reachable: 0 bytes in 0 blocks
    ==16719==         suppressed: 0 bytes in 0 blocks
    ==16719== Rerun with --leak-check=full to see details of leaked memory
    ==16719==
    ==16719== For lists of detected and suppressed errors, rerun with: -s
    ==16719== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

**四 分析**

1 16719表示的是进程号

2 版本信息

==16719== Memcheck, a memory error detector
    ==16719== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
    ==16719== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
    ==16719== Command: ./0508

3 非法写内存，写操作内存是4个字节，发生错误时候的函数堆栈，说明错误发生在第6行

==16719== Invalid write of size 4
    ==16719==    at 0x4008DE: func() (0508test.cpp:6)
    ==16719==    by 0x4008EE: main (0508test.cpp:9)

4 程序泄露了40个字节的内存

==16719== LEAK SUMMARY:
    ==16719==    definitely lost: 40 bytes in 1 blocks
    ==16719==    indirectly lost: 0 bytes in 0 blocks
    ==16719==      possibly lost: 0 bytes in 0 blocks
    ==16719==    still reachable: 0 bytes in 0 blocks
    ==16719==         suppressed: 0 bytes in 0 blocks

5 该程序存在两个问题，一个是fun函数动态申请的堆内存没有释放，另外一个是对堆内存访问越界。这两个问题都被valgrind检测出来了。