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/