Valgrind 使用简单说明

应用 Valgrind 发现 Linux 程序的内存问题

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

原文链接：http://blog.csdn.net/ecjtuync/archive/2009/12/01/4909364.aspx

Valgrind 使用简单说明

Valgrind
是一个GPL的软件，用于Linux（For x86, amd64 and ppc32）程序的内存调试和代码剖析。你可以在它的环境中运行你的程序来监视内存的使用
情况，比如C 语言中的malloc和free或者 C++中的new和 delete。使用
Valgrind
的工具包，你可以自动的检测许多内存管理和线程的bug，避免花费太多的时间在bug寻找上，使得你的程序更加稳固。

Valgrind 是在linux系统下开发应用程序时用于调试内存问题的工具。它尤其擅长发现内存管理的问题，它可以检查程序运行时的内存泄漏问题。
它的官方网址是 http://www.valgrind.org/

下载最新版本的Valgrind，目前是3.2.0。 wget http://www.valgrind.org/downloads/valkyrie-1.2.0.tar.bz2

执行常规的安装步骤：./confgure && make && make install。注意： 系统必须安装QT的开发包。即便这样在make 时还是出现qplatformdefs.h这个文件找不到的情况，导致make失败。查找系统中的qplatformdefs.h 之后，发现没有存在于qt的标准头文件目录/usr/lib/qt-3.3/include。如是将/usr/lib/qt- 3.3/mkspecs/linux-g++/ 目录下该头文件复制标准头文件目录，重新make ，后面一切OK。

初次使用

编译如下代码:  gcc -Wall example.c -g -o example

#include <stdlib.h> void f(void) { int* x = malloc(10 * sizeof(int)); x[10] = 0; // problem 1: heap block overrun } // problem 2: memory leak -- x not freed int main(void) { f(); return 0; }

注意：gcc 的-g 选项让Valgrind调试输出时指出相应信息的代码所在的行号。

valgrind --tool=memcheck --leak-check=yes ./example

==6742== Memcheck, a memory error detector for x86-linux. ==6742== Copyright (C) 2002-2004, and GNU GPL'd, by Julian Seward et al. ==6742== Using valgrind-2.2.0, a program supervision framework for x86-linux. ==6742== Copyright (C) 2000-2004, and GNU GPL'd, by Julian Seward et al. ==6742== For more details, rerun with: -v ==6742== ==6742== Invalid write of size 4 ==6742== at 0x8048384: f (example.c:6) ==6742== by 0x80483AC: main (example.c:12) ==6742== Address 0x1B908050 is 0 bytes after a block of size 40 alloc'd ==6742== at 0x1B904984: malloc (vg_replace_malloc.c:131) ==6742== by 0x8048377: f (example.c:5) ==6742== by 0x80483AC: main (example.c:12) ==6742== ==6742== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 12 from 1) ==6742== malloc/free: in use at exit: 40 bytes in 1 blocks. ==6742== malloc/free: 1 allocs, 0 frees, 40 bytes allocated. ==6742== For counts of detected errors, rerun with: -v ==6742== searching for pointers to 1 not-freed blocks. ==6742== checked 1360800 bytes. ==6742== ==6742== ==6742== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1 ==6742== at 0x1B904984: malloc (vg_replace_malloc.c:131) ==6742== by 0x8048377: f (example.c:5) ==6742== by 0x80483AC: main (example.c:12) ==6742== ==6742== LEAK SUMMARY: ==6742== definitely lost: 40 bytes in 1 blocks. ==6742== possibly lost: 0 bytes in 0 blocks. ==6742== still reachable: 0 bytes in 0 blocks. ==6742== suppressed: 0 bytes in 0 blocks. ==6742== Reachable blocks (those to which a pointer was found) are not shown. ==6742== To see them, rerun with: --show-reachable=yes

上面的C程序存在两个错误：1. 数组下标越界；2. 分配的内存没有释放，存在内存泄露的问题。对于错误1，看Valgrind的调试信息片断

==6742== Invalid write of size 4 ==6742== at 0x8048384: f (example.c:6) ==6742== by 0x80483AC: main (example.c:12) ==6742== Address 0x1B908050 is 0 bytes after a block of size 40 alloc'd ==6742== at 0x1B904984: malloc (vg_replace_malloc.c:131) ==6742== by 0x8048377: f (example.c:5)

对于错误2，看这个
==6742== malloc/free: 1 allocs, 0 frees, 40 bytes allocated.

......

==6742== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1

==6742== at 0x1B904984: malloc (vg_replace_malloc.c:131)

==6742== by 0x8048377: f (example.c:5)

==6742== by 0x80483AC: main (example.c:12)

Valgrind
的主要功能

Valgrind
工具包包含多个工具，如Memcheck,Cachegrind,Helgrind, Callgrind，Massif。下面分别介绍个工具的作用：

Memcheck 工具主要检查下面的程序错误：

使用
未初始化的内存 (Use of uninitialised memory)

使用
已经释放了的内存 (Reading/writing memory after it has been free’d)

使用
超过 malloc分配的内存空间(Reading/writing off the end of malloc’d blocks)

对堆栈的非法访问 (Reading/writing inappropriate areas on the stack)

申请的空间是否有释放 (Memory leaks – where pointers to malloc’d blocks are lost forever)

malloc/free/new/delete申请和释放内存的匹配(Mismatched use of malloc/new/new [] vs free/delete/delete [])

src和dst的重叠(Overlapping src and dst pointers in memcpy() and related functions)

Callgrind

Callgrind收集程序运行时的一些数据，函数调用关系等信息，还可以有选择地进行cache 模拟。在运行结束时，它会把分析数据写入一个文件。callgrind_annotate可以把这个文件的内容转化成可读的形式。

Cachegrind

它模拟 CPU中的一级缓存I1,D1和L2二级缓存，能够精确地指出程序中 cache的丢失和命中。如果需要，它还能够为我们提供cache丢失次数，内存引用次数，以及每行代码，每个函数，每个模块，整个程序产生的指令数。这对优化程序有很大的帮助。

Helgrind

它主要用来检查多线程程序中出现的竞争问题。Helgrind 寻找内存中被多个线程访问，而又没有一贯加锁的区域，这些区域往往是线程之间失去同步的地方，而且会导致难以发掘的错误。Helgrind实现了名为” Eraser” 的竞争检测算法，并做了进一步改进，减少了报告错误的次数。

Massif

堆栈分析器，它能测量程序在堆栈中使用
了多少内存，告诉我们堆块，堆管理块和栈的大小。Massif能帮助我们减少内存的使用
，在带有虚拟内存的现代系统中，它还能够加速我们程序的运行，减少程序停留在交换区中的几率。

Valgrind
安装

1、 到www.valgrind
.org下载最新版valgrind
-3.2.3.tar.bz2

2、 解压安装包：tar –jxvf valgrind
-3.2.3.tar.bz2

3、 解压后生成目录valgrind
-3.2.3

4、 cd valgrind
-3.2.3

5、 ./configure

6、 Make;make install

Valgrind
使用

用法: valgrind
[options] prog-and-args [options]: 常用选项，适用于所有Valgrind
工具

-tool=<name> 最常用的选项。运行 valgrind
中名为toolname的工具。默认memcheck。

h –help 显示帮助信息。

-version 显示valgrind
内核的版本，每个工具都有各自的版本。

q –quiet 安静地运行，只打印错误信息。

v –verbose 更详细的信息, 增加错误数统计。

-trace-children=no|yes 跟踪子线程? [no]

-track-fds=no|yes 跟踪打开的文件描述？[no]

-time-stamp=no|yes 增加时间戳到LOG信息? [no]

-log-fd=<number> 输出LOG到描述符文件 [2=stderr]

-log-file=<file> 将输出的信息写入到filename.PID的文件里，PID是运行程序的进行ID

-log-file-exactly=<file> 输出LOG信息到 file

-log-file-qualifier=<VAR> 取得环境变量的值来做为输出信息的文件名。 [none]

-log-socket=ipaddr:port 输出LOG到socket ，ipaddr:port

LOG信息输出

-xml=yes 将信息以xml格式输出，只有memcheck可用

-num-callers=<number> show <number> callers in stack traces [12]

-error-limit=no|yes 如果太多错误，则停止显示新错误? [yes]

-error-exitcode=<number> 如果发现错误则返回错误代码 [0=disable]

-db-attach=no|yes 当出现错误，valgrind
会自动启动调试器gdb。[no]

-db-command=<command> 启动调试器的命令行选项[gdb -nw %f %p]

适用于Memcheck工具的相关选项：

-leak-check=no|summary|full 要求对leak给出详细信息? [summary]

-leak-resolution=low|med|high how much bt merging in leak check [low]

-show-reachable=no|yes show reachable blocks in leak check? [no]

Valgrind
使用
举例

下面是一段有问题的C程序代码test.c

#include <stdlib.h>

void f(void)

{

int* x = malloc(10 * sizeof(int));

x[10] = 0;  //问题1: 数组下标越界

}                  //问题2: 内存没有释放

int main(void)

{

f();

return 0;

}

1、 编译程序test.c

gcc -Wall test.c -g -o test

2、 使用
Valgrind
检查程序BUG

valgrind
--tool=memcheck --leak-check=full ./test

3、 分析输出的调试信息

==3908== Memcheck, a memory error detector.

==3908== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.

==3908== Using LibVEX rev 1732, a library for dynamic binary translation.

==3908== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.

==3908== Using valgrind
-3.2.3, a dynamic binary instrumentation framework.

==3908== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.

==3908== For more details, rerun with: -v

==3908==

--3908-- DWARF2 CFI reader: unhandled CFI instruction 0:50

--3908-- DWARF2 CFI reader: unhandled CFI instruction 0:50

/*数组越界错误*/

==3908== Invalid write of size 4

==3908==    at 0x8048384: f (test.c:6)

==3908==    by 0x80483AC: main (test.c:11)

==3908==  Address 0x400C050 is 0 bytes after a block of size 40 alloc'd

==3908==    at 0x40046F2: malloc (vg_replace_malloc.c:149)

==3908==    by 0x8048377: f (test.c:5)

==3908==    by 0x80483AC: main (test.c:11)

==3908==

==3908== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 14 from 1)

==3908== malloc/free: in use at exit: 40 bytes in 1 blocks.

==3908== malloc/free: 1 allocs, 0 frees, 40 bytes allocated.

==3908== For counts of detected errors, rerun with: -v

==3908== searching for pointers to 1 not-freed blocks.

==3908== checked 59,124 bytes.

==3908==

==3908==

/*有内存空间没有释放*/

==3908== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1

==3908==    at 0x40046F2: malloc (vg_replace_malloc.c:149)

==3908==    by 0x8048377: f (test.c:5)

==3908==    by 0x80483AC: main (test.c:11)

==3908==

==3908== LEAK SUMMARY:

==3908==    definitely lost: 40 bytes in 1 blocks.

==3908==      possibly lost: 0 bytes in 0 blocks.

==3908==    still reachable: 0 bytes in 0 blocks.

==3908==         suppressed: 0 bytes in 0 blocks

另外参考文章：http://blog.csdn.net/ShowMan/archive/2009/07/31/4397841.aspx

http://blog.csdn.net/zhangxuez/archive/2007/08/28/1761489.aspx