操作系统 2023-08-04

如何使用Valgrind内存检查工具检查C/C++中内存泄露 (linux c 检查内存泄露)

使用 Valgrind Memcheck

memcheck工具的使用方式如下:

valgrind –tool=memcheck ./a.out

从上面的命令可以清楚的看到, 主要的命令是valgrind，而我们想使用的工具是通过’-tool’选项来指定的. 上面的‘a.out’指的是我们想使用memcheck运行的可执行文件.

该工具可以检测下列与内存相关的问题 :

未释放内存的使用

对释放后内存的读/写

对已分配内存块尾部的读/写

内存泄露

不匹配的使用malloc/new/new 和 free/delete/delete

重做腔肆复释放内存

注意: 上面列出的并不很全面，但却包含了能被该工具检测到的很多普遍的问题.

让我们一圆租个一个地对上面的场景进行讨论:

注意: 下面讨论的所有测试代码都应该使用gcc并且加上-g选项(用来在memcheck的输出中生成行号)进行编译. 就想我们之前讨论过的 C程序被编译成可执行文件, 它需要经历四个不同的阶段.

ToB蓝波湾

翻译于 1 年前

0人顶

顶翻译的不错哦!

1. 使纯轿用未初始化的内存

Code :

#include

int main(void)

{

char *p;

char c = *p;

printf(“\n \n”,c);

return 0;

}

在上面的代码中，我们尝试使用未初始化的指针 ‘p’.

让我们运行Memcheck来看下结果.

$ valgrind –tool=memcheck ./val

==2862== Memcheck, a memory error detector

==2862== Copyright (C), and GNU GPL’d, by Julian Seward et al.

==2862== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for copyright info

==2862== Command: ./val

==2862==

==2862== Use of uninitialised value of size 8

==2862== at 0x400530: main (valgrind.c:8)

==2862==

==2862== HEAP SUMMARY:

==2862== in use at exit: 0 bytes in 0 blocks

==2862== total heap usage: 0 allocs, 0 frees, 0 bytes allocated

==2862==

==2862== All heap blocks were freed — no leaks are possible

==2862==

==2862== For counts of detected and suppressed errors, rerun with: -v

==2862== Use –track-origins=yes to see where uninitialized values come from

==2862== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)

从上面的输出可以看到,Valgrind检测到了未初始化的变量，然后给出了警告(上面加粗的几行(译者注：貌似上面没有加粗的)).

2. 在内存被释放后进行读/写

Code :

#include

int main(void)

{

char *p = malloc(1);

*p = ‘a’;

char c = *p;

printf(“\n \n”,c);

free(p);

c = *p;

return 0;

}

上面的代码中，我们有一个释放了内存的指针 ‘p’ 然后我们又尝试利用指针获取值.

让我们运行memcheck来看一下Valgrind对这种情况是如何反应的.

$ valgrind –tool=memcheck ./val

==2849== Memcheck, a memory error detector

==2849== Copyright (C), and GNU GPL’d, by Julian Seward et al.

==2849== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for copyright info

==2849== Command: ./val

==2849==

==2849== Invalid read of size 1

==2849== at 0x400603: main (valgrind.c:30)

==2849== Address 0x51b0040 is 0 bytes inside a block of size 1 free’d

==2849== at 0x4C270BD: free (vg_replace_malloc.c:366)

==2849== by 0x4005FE: main (valgrind.c:29)

==2849==

==2849== HEAP SUMMARY:

==2849== in use at exit: 0 bytes in 0 blocks

==2849== total heap usage: 1 allocs, 1 frees, 1 bytes allocated

==2849==

==2849== All heap blocks were freed — no leaks are possible

==2849==

==2849== For counts of detected and suppressed errors, rerun with: -v

==2849== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)

从上面的输出内容可以看到，Valgrind检测到了无效的读取操作然后输出了警告 ‘Invalid read of size 1′.

另注,使用gdb来调试c程序.

3. 从已分配内存块的尾部进行读/写

Code :

#include

int main(void)

{

char *p = malloc(1);

*p = ‘a’;

char c = *(p+1);

printf(“\n \n”,c);

free(p);

return 0;

}

在上面的代码中，我们已经为‘p’分配了一个字节的内存,但我们在将值读取到 ‘c’中的时候使用的是地址p+1.

现在我们使用Valgrind运行上面的代码 :

$ valgrind –tool=memcheck ./val

==2835== Memcheck, a memory error detector

==2835== Copyright (C), and GNU GPL’d, by Julian Seward et al.

==2835== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for copyright info

==2835== Command: ./val

==2835==

==2835== Invalid read of size 1

==2835== at 0x4005D9: main (valgrind.c:25)

==2835== Address 0x51b0041 is 0 bytes after a block of size 1 alloc’d

==2835== at 0x4C274A8: malloc (vg_replace_malloc.c:236)

==2835== by 0x4005C5: main (valgrind.c:22)

==2835==

==2835== HEAP SUMMARY:

==2835== in use at exit: 0 bytes in 0 blocks

==2835== total heap usage: 1 allocs, 1 frees, 1 bytes allocated

==2835==

==2835== All heap blocks were freed — no leaks are possible

==2835==

==2835== For counts of detected and suppressed errors, rerun with: -v

==2835== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)

同样，该工具在这种情况下也检测到了无效的读取操作.

4. 内存泄露

Code:

#include

int main(void)

{

char *p = malloc(1);

*p = ‘a’;

char c = *p;

printf(“\n \n”,c);

return 0;

}

在这次的代码中, 我们申请了一个字节但是没有将它释放.现在让我们运行Valgrind看看会发生什么：

$ valgrind –tool=memcheck –leak-check=full ./val

==2888== Memcheck, a memory error detector

==2888== Copyright (C), and GNU GPL’d, by Julian Seward et al.

==2888== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for copyright info

==2888== Command: ./val

==2888==

==2888== HEAP SUMMARY:

==2888== in use at exit: 1 bytes in 1 blocks

==2888== total heap usage: 1 allocs, 0 frees, 1 bytes allocated

==2888==

==2888== 1 bytes in 1 blocks are definitely lost in loss record 1 of 1

==2888== at 0x4C274A8: malloc (vg_replace_malloc.c:236)

==2888== by 0x400575: main (valgrind.c:6)

==2888==

==2888== LEAK SUMMARY:

==2888== definitely lost: 1 bytes in 1 blocks

==2888== indirectly lost: 0 bytes in 0 blocks

==2888== possibly lost: 0 bytes in 0 blocks

==2888== still reachable: 0 bytes in 0 blocks

==2888==suppressed: 0 bytes in 0 blocks

==2888==

==2888== For counts of detected and suppressed errors, rerun with: -v

==2888== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 4 from 4)

输出行(上面加粗的部分)显示，该工具能够检测到内存的泄露.

2、大家谁用过valgrind，linux下面检测内存泄露的一款软件，安装后输入：valgrind ls -l 提示

这应该是你的系统环境有问题了。

命令是肯定没问题的

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