Valgrind检测非法访问内存

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。