简介：

Valgrind是一款用于内存调试、内存泄漏检测以及性能分析的软件开发工具。

使用方法：

vargrind  --tool=memcheck ./a.out

如果需要日志，则添加

vargrind –log-file=var.log –tool=memcheck ./a.out

常用的options： –track-origins=yes –leak-check=full –num-callers=*

1.内存泄露：

#include <stdio.h>

void function()
{
    int *p = (int*)malloc(10*sizeof(int));
    p[10] = 0;
}

int main()
{
    function();

    return 0;
}

相关日志：

==20220== Memcheck, a memory error detector
==20220== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==20220== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
==20220== Command: ./test
==20220== Parent PID: 20160
==20220==
==20220== Invalid write of size 4
==20220==    at 0x80483FF: function (in /mnt/Documents/Training/valgrind/test)
==20220==    by 0x8048411: main (in /mnt/Documents/Training/valgrind/test)
==20220==  Address 0x41be050 is 0 bytes after a block of size 40 alloc'd
==20220==    at 0x4028876: malloc (vg_replace_malloc.c:236)
==20220==    by 0x80483F5: function (in /mnt/Documents/Training/valgrind/test)
==20220==    by 0x8048411: main (in /mnt/Documents/Training/valgrind/test)
==20220==
==20220==
==20220== HEAP SUMMARY:
==20220==     in use at exit: 40 bytes in 1 blocks
==20220==   total heap usage: 1 allocs, 0 frees, 40 bytes allocated
==20220==
==20220== LEAK SUMMARY:
==20220==    definitely lost: 40 bytes in 1 blocks
==20220==    indirectly lost: 0 bytes in 0 blocks
==20220==      possibly lost: 0 bytes in 0 blocks
==20220==    still reachable: 0 bytes in 0 blocks
==20220==         suppressed: 0 bytes in 0 blocks
==20220== Rerun with --leak-check=full to see details of leaked memory
==20220==
==20220== For counts of detected and suppressed errors, rerun with: -v
==20220== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 11 from 6)

2.使用未初始化的内存

#include <stdio.h>

int main()
{
    int a;
    if (a==1)
    {
        printf("a==%d\n",a);
    }

    return 0;
}

日志分析：

==20345== Memcheck, a memory error detector
==20345== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==20345== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
==20345== Command: ./test
==20345==
==20345== Conditional jump or move depends on uninitialised value(s)
==20345==    at 0x80483F2: main (in /mnt/Documents/Training/valgrind/test)
==20345==
==20345==
==20345== HEAP SUMMARY:
==20345==     in use at exit: 0 bytes in 0 blocks
==20345==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==20345==
==20345== All heap blocks were freed -- no leaks are possible
==20345==
==20345== For counts of detected and suppressed errors, rerun with: -v
==20345== Use --track-origins=yes to see where uninitialised values come from
==20345== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 11 from 6)

可以使用--track-origins=yes 得到更多的信息

3.内存读写越界

#include <stdio.h>

int main()
{
    int *a = (int*)malloc(5*sizeof(int));
    a[5] = 1;

    return 0;
}

==20368== Memcheck, a memory error detector
==20368== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==20368== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
==20368== Command: ./test
==20368==
==20368== Invalid write of size 4
==20368==    at 0x8048404: main (in /mnt/Documents/Training/valgrind/test)
==20368==  Address 0x41be03c is 0 bytes after a block of size 20 alloc'd
==20368==    at 0x4028876: malloc (vg_replace_malloc.c:236)
==20368==    by 0x80483F8: main (in /mnt/Documents/Training/valgrind/test)
==20368==
==20368==
==20368== HEAP SUMMARY:
==20368==     in use at exit: 20 bytes in 1 blocks
==20368==   total heap usage: 1 allocs, 0 frees, 20 bytes allocated
==20368==
==20368== LEAK SUMMARY:
==20368==    definitely lost: 20 bytes in 1 blocks
==20368==    indirectly lost: 0 bytes in 0 blocks
==20368==      possibly lost: 0 bytes in 0 blocks
==20368==    still reachable: 0 bytes in 0 blocks
==20368==         suppressed: 0 bytes in 0 blocks
==20368== Rerun with --leak-check=full to see details of leaked memory
==20368==
==20368== For counts of detected and suppressed errors, rerun with: -v
==20368== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 11 from 6)

4.内存申请释放管理错误

#include <stdio.h>

int main()
{
    int *a = new int[5];

    /*free(a);*/
    delete a;

    return 0;
}

==20387== Memcheck, a memory error detector
==20387== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==20387== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
==20387== Command: ./test
==20387==
==20387== Mismatched free() / delete / delete []
==20387==    at 0x4027919: operator delete(void*) (vg_replace_malloc.c:387)
==20387==    by 0x8048498: main (in /mnt/Documents/Training/valgrind/test)
==20387==  Address 0x42f2028 is 0 bytes inside a block of size 20 alloc'd
==20387==    at 0x4027F65: operator new[](unsigned int) (vg_replace_malloc.c:299)
==20387==    by 0x8048488: main (in /mnt/Documents/Training/valgrind/test)
==20387==
==20387==
==20387== HEAP SUMMARY:
==20387==     in use at exit: 0 bytes in 0 blocks
==20387==   total heap usage: 1 allocs, 1 frees, 20 bytes allocated
==20387==
==20387== All heap blocks were freed -- no leaks are possible
==20387==
==20387== For counts of detected and suppressed errors, rerun with: -v
==20387== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 17 from 6)

这里只是简单的测试了几个例子，有兴趣的读者可以参考下面的url。

参考：

http://www.ibm.com/developerworks/cn/linux/l-cn-valgrind/