valgrind 性能测试工具学习使用

1、valgrind简介

Valgrind工具套件提供了许多调试和分析工具，可帮助您使程序更快，更正确。这些工具中最受欢迎的是Memcheck。它能够检测许多与C和C ++程序中常见的内存相关的错误，这些错误可能致使崩溃和不可预测的行为。

标准配置提供了许多有用的工具：

1. Memcheck是一个内存错误检测器。能够帮助你使程序更加正确。——这是valgrind应用最普遍的工具，一个重量级的内存检查器，可以发现开发中绝大多数内存错误使用状况，好比：使用未初始化的内存，使用已经释放了的内存，内存访问越界等。
2. Cachegrind是一个缓存和分支预测分析器。能够帮助程序运行的更快。——它主要用来检查程序中缓存使用出现的问题。
3. Callgrind是一个生成缓存分析器的调用图。和Cachegrind有一些重叠，也收集了Cachegrind没有的一些信息。——它主要用来检查程序中函数调用过程当中出现的问题。
4. Helgrind是一个线程错误检测器。能够帮助多线程程序更准确。——它主要用来检查多线程程序中出现的竞争问题。
5. DRD也是线程错误检测器。他与Helgrind相似，可是用不一样的分析技术，所以可能会发现不一样的问题。
6. Massif时一个堆分析器。能够帮助使程序使用更少的内存。——它主要用来检查程序中堆栈使用中出现的问题。
7. DHAT时一种不一样类型的对分析器。能够帮助了解块寿命，块利用率和效率低下的问题。
8. SGcheck时一种实验工具，能够检测堆栈和全局数组的溢出。它的功能与Memcheck的功能互补：SGcheck发现Memcheck没法解决的问题，反之亦然。
9. 小工具： Lackey是一个示例工具，用于说明一些仪器基础知识和
10. 小工具：Nulgrind是最小的Valgrind工具，不进行分析或检测，仅用于测试目的。是最简单的Valgrind工具。它不执行任何程序或程序分析，只需正常运行便可。它主要用于Valgrind的开发人员进行调试和回归测试。尽管如此，您可使用Nulgrind运行程序。它们的运行速度比正常状况慢5倍左右，没有任何有用的效果。Note that you need to use the option --tool=none to run Nulgrind (ie. not --tool=nulgrind).
11. extension ------> 能够利用core提供的功能，本身编写特定的内存调试工具（不在我学习的范围中）

 2、Ubuntu16.04下安装valgrind

Valgrind 安装，去官网下载： http://valgrind.org/downloads/current.html#current

我当前下载的版本为valgrind-3.15.0.tar.bz2

# tar -jxf valgrind-3.15.0.tar.bz2 ——解压 # cd /home/ranxf/valgrind-3.15.0 # vim README ——查看文档来确认安装过程 　0. Clone the code from GIT: git clone git://sourceware.org/git/valgrind.git There are further instructions at http://www.valgrind.org/downloads/repository.html. 　1. cd into the source directory. 2. Run ./autogen.sh to setup the environment (you need the standard autoconf tools to do so). 3. Continue with the following instructions... 　　To install from a tar.bz2 distribution: 4. Run ./configure, with some options if you wish. The only interesting one is the usual --prefix=/where/you/want/it/installed. 5. Run "make". 6. Run "make install", possibly as root if the destination permissions require that. 7. See if it works. Try "valgrind ls -l". Either this works, or it bombs out with some complaint. In that case, please let us know (see http://valgrind.org/support/bug_reports.html). # ./configure --prefix=/workdisk/valgrind/ # 配置安装路径 # make # 从makefile中读取指令，而后编译 # make instal # 从makefile中读取指令，安装到指定位置

# vim /etc/profile
export PATH="$PATH:/workdisk/valgrind/bin"（环境变量配置）

3、验证valgrind是否安装成功

cd /workdisk/valgrind/bin

# ./valgrind ls -l ==31242== Memcheck, a memory error detector ==31242== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==31242== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==31242== Command: ls -l ==31242== 总用量 836 -rwxr-xr-x 1 root root 44737 8月 27 10:41 callgrind_annotate -rwxr-xr-x 1 root root 12673 8月 27 10:41 callgrind_control -rwxr-xr-x 1 root root 33535 8月 27 10:41 cg_annotate -rwxr-xr-x 1 root root 10418 8月 27 10:41 cg_diff -rwxr-xr-x 1 root root 315872 8月 27 10:41 cg_merge -rwxr-xr-x 1 root root 24398 8月 27 10:41 ms_print -rwxr-xr-x 1 root root 76816 8月 27 10:41 valgrind -rwxr-xr-x 1 root root 104136 8月 27 10:41 valgrind-di-server -rwxr-xr-x 1 root root 30176 8月 27 10:41 valgrind-listener -rwxr-xr-x 1 root root 180680 8月 27 10:41 vgdb ==31242== ==31242== HEAP SUMMARY: ==31242== in use at exit: 19,848 bytes in 17 blocks ==31242== total heap usage: 228 allocs, 211 frees, 102,284 bytes allocated ==31242== ==31242== LEAK SUMMARY: ==31242== definitely lost: 0 bytes in 0 blocks ==31242== indirectly lost: 0 bytes in 0 blocks ==31242== possibly lost: 0 bytes in 0 blocks ==31242== still reachable: 19,848 bytes in 17 blocks ==31242== suppressed: 0 bytes in 0 blocks ==31242== Rerun with --leak-check=full to see details of leaked memory ==31242== ==31242== For lists of detected and suppressed errors, rerun with: -s ==31242== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

./valgrind --leak-check=full ls -l ==31322== Memcheck, a memory error detector ==31322== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==31322== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==31322== Command: ls -l ==31322== 总用量 836 -rwxr-xr-x 1 root root 44737 8月 27 10:41 callgrind_annotate -rwxr-xr-x 1 root root 12673 8月 27 10:41 callgrind_control -rwxr-xr-x 1 root root 33535 8月 27 10:41 cg_annotate -rwxr-xr-x 1 root root 10418 8月 27 10:41 cg_diff -rwxr-xr-x 1 root root 315872 8月 27 10:41 cg_merge -rwxr-xr-x 1 root root 24398 8月 27 10:41 ms_print -rwxr-xr-x 1 root root 76816 8月 27 10:41 valgrind -rwxr-xr-x 1 root root 104136 8月 27 10:41 valgrind-di-server -rwxr-xr-x 1 root root 30176 8月 27 10:41 valgrind-listener -rwxr-xr-x 1 root root 180680 8月 27 10:41 vgdb ==31322== ==31322== HEAP SUMMARY: ==31322== in use at exit: 19,848 bytes in 17 blocks ==31322== total heap usage: 228 allocs, 211 frees, 102,284 bytes allocated ==31322== ==31322== LEAK SUMMARY: ==31322== definitely lost: 0 bytes in 0 blocks ==31322== indirectly lost: 0 bytes in 0 blocks ==31322== possibly lost: 0 bytes in 0 blocks ==31322== still reachable: 19,848 bytes in 17 blocks ==31322== suppressed: 0 bytes in 0 blocks ==31322== Reachable blocks (those to which a pointer was found) are not shown. ==31322== To see them, rerun with: --leak-check=full --show-leak-kinds=all ==31322== ==31322== For lists of detected and suppressed errors, rerun with: -s ==31322== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

4、Valgrind 命令参数介绍

用法: valgrind [options] prog-and-args
[options]: 经常使用选项，适用于全部Valgrind工具

最经常使用的命令格式：

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

 -h –help 显示帮助信息。（除了如下参数，可用帮助-h查看更多信息） --version 显示valgrind内核的版本，每一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, 增长错误数统计。 --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 增长时间戳到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作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

仍是在-h中查看

 　　--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 若是太多错误，则中止显示新错误? [yes] --error-exitcode=<number> 若是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]

5、测试案例介绍

（一）测试demo

/workdisk# vim /workdisk/testcode/testValgrind.cc  # 在该路径下生成喊如下内容的testValgrind.cc文件（内存未释放）

#include <iostream>

using namespace std; int main() { int *a = new int(2); //delete a;

    return 0; }

（二）代码编译

root@ranxf-TEST:/workdisk/testcode# ls testValgrind.cc root@ranxf-TEST:/workdisk/testcode# g++ -g -o testValgrind testValgrind.cc root@ranxf-TEST:/workdisk/testcode# ls testValgrind testValgrind.cc

-o：指定生成可执行文件的名称。使用方法为：g++ -o afile file.cpp file.h ... （可执行文件不可与待编译或连接文件同名，不然会生成相应可执行文件且覆盖原编译或连接文件），若是不使用-o选项，则会生成默承认执行文件a.out。
-c：只编译不连接，只生成目标文件。
-g：添加gdb调试选项。

（三）代码单元测试

输入命令：orkdisk/testcode# /workdisk/valgrind/bin/valgrind --tool=memcheck --leak-check=full ./testValgrind
若是valgrind添加了环境变量，输入命令能够在任何路径下简化为：#valgrind --tool=memcheck --leak-check=full ./testValgrin

root@ranxf-TEST:/workdisk/testcode# /workdisk/valgrind/bin/valgrind --tool=memcheck --leak-check=full ./testValgrind ==12862== Memcheck, a memory error detector # 内存错误检测器 ==12862== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==12862== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==12862== Command: ./testValgrind ==12862== 
==12862== 
==12862== HEAP SUMMARY: # 堆摘要 ==12862==     in use at exit: 72,708 bytes in 2 blocks # 退出时使用：2个数据块中有72708个字节 ==12862==   total heap usage: 2 allocs, 0 frees, 72,708 bytes allocated ==12862== 
==12862== 4 bytes in 1 blocks are definitely lost in loss record 1 of 2 # 1个块中的4个字节在丢失记录1（共2个）中确定丢失
==12862==    at 0x4C2E4B6: operator new(unsigned long) (vg_replace_malloc.c:344) ==12862==    by 0x400717: main (testValgrind.cc:7) ==12862== 
==12862== LEAK SUMMARY: 泄漏汇总 ==12862==    definitely lost: 4 bytes in 1 blocks 确定泄露：1块中有4个字节 ==12862==    indirectly lost: 0 bytes in 0 blocks 间接泄露：0块0字节 ==12862==      possibly lost: 0 bytes in 0 blocks 可能泄露：0块0字节 ==12862==    still reachable: 72,704 bytes in 1 blocks 仍然能够访问：1个块中有72704个字节 ==12862==         suppressed: 0 bytes in 0 blocks 抑制：0块0字节 ==12862== Reachable blocks (those to which a pointer was found) are not shown. 不显示可访问块（找到指针的块）。 ==12862== To see them, rerun with: --leak-check=full --show-leak-kinds=all 若要查看它们，请使用如下项从新运行：--leak check=full--show leak kinds=all ==12862== 
==12862== For lists of detected and suppressed errors, rerun with: -s 对于检测到的和抑制的错误列表，请使用-s从新运行。 ==12862== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) 错误摘要：1个上下文中有1个错误（禁止：0到0） root@ranxf-TEST:/workdisk/testcode#

Memcheck将内存泄露分为两种，一种是确定的内存泄露（definitely lost），一种可能的内存泄露（possibly lost）；

Definitely lost 是指已经不可以访问这块内存；

　　Definitely lost又分为两种：直接的（direct）泄露和间接的（indirect）泄露

　　　　直接泄露是没有任何指针指向该内存；

　　　　间接泄露是指指向该内存的指针都位于内存泄露处；

Possibly lost 是指仍然存在某个指针可以访问某块内存，但该指针指向的已经不是该内存首地址。

 （四）测试代码

代码1. 使用未初始化的内存（程序名为valgrindTestCode1.cpp ）

#include <iostream>
using namespace std; int main() { int a[5]; int i,s=0; a[0]=a[1]=a[3]=a[4]=0; for(i=0;i<5;i++) s=s+a[i]; if(s==33) cout<<"sum is 33"<<endl; else cout<<"sum is not 33"<<endl; return 0; }

数组a中的第二个元素未进行初始化，可是在for循环中依然访问链数组a的第二个元素。这就是使用未初始化的元素问题。在使用g++编译器对该程序编译并运行，结果以下：

root@ranxf-TEST:/workdisk/testcode# g++ -g -o TectCode1 valgrindTestCode1.cpp root@ranxf-TEST:/workdisk/testcode# ls TectCode1 testValgrind testValgrind.cc valgrindTestCode1.cpp root@ranxf-TEST:/workdisk/testcode# ./TectCode1 sum is not 33

程序在编译和运行过程当中并无报出任何错误，异常和警告。

但实际上，程序存在一个巨大的隐患，那就是对未初始化的内存进行访问。咱们使用valgrind对该程序进行检测，结果以下所示：

root@ranxf-TEST:/workdisk/testcode# valgrind ./TectCode1 或者 valgrind --tool=memcheck --leak-check=full ./TectCode1 #　valgrind默认为内存错误检测器 ==22985== Memcheck, a memory error detector ==22985== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==22985== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==22985== Command: ./TectCode1 ==22985== 
==22985== Conditional jump or move depends on uninitialised value(s) ==22985== at 0x400910: main (valgrindTestCode1.cpp:10) （此处要求咱们在进行g++编译时添加-g参数，否则便给不出具体行数的提示） ==22985== sum is not 33
==22985== 
==22985== HEAP SUMMARY: ==22985==     in use at exit: 72,704 bytes in 1 blocks ==22985==   total heap usage: 2 allocs, 1 frees, 73,728 bytes allocated ==22985== 
==22985== LEAK SUMMARY: ==22985==    definitely lost: 0 bytes in 0 blocks ==22985==    indirectly lost: 0 bytes in 0 blocks ==22985==      possibly lost: 0 bytes in 0 blocks ==22985==    still reachable: 72,704 bytes in 1 blocks ==22985==         suppressed: 0 bytes in 0 blocks ==22985== Rerun with --leak-check=full to see details of leaked memory

从上图结果中能够清晰的看到，提示出1个错误，提示信息为：“Conditional jump or move depends on uninitialised value(s)”，而且提示了错误位置在源文件test1.cpp中的第10行（此处要求咱们在进行g++编译时添加-g参数，否则便给不出具体行数的提示）。

代码2：内存读写越界

 1 #include <stdlib.h>
 2 #include <iostream>
 3 using namespace std;  4 int main()  5 {  6     int len=4;  7     int *pt=(int *)malloc(len*sizeof(int));  8     int *p=pt;  9     for(int i=0;i<len;i++) 10       p++; 11     *p=5; 12     cout<<"the value of p is"<<*p<<endl; 13     return 0; 14 }

在程序2中，p指针首先指向了malloc出的4个字节的地址。
以后执行了四次自增运算。也就是p指针自增运算后与初始地址相比偏移了32个字节。
偏移后的地址空间在程序中并无申请。因此，p指针变成链野指针。
程序中而且又对p的地址空间进行写操做。这就形成链内存读写越界的问题。

 ———————————————— 
在使用g++编译器对该程序编译并运行，结果以下： root@ranxf-TEST:/workdisk/testcode# g++ -g -o TestCode2 valgrindTestCode2.cpp root@ranxf-TEST:/workdisk/testcode# ./TestCode2 the value of p is5

/workdisk/testcode# valgrind ./TestCode2 ==26714== Memcheck, a memory error detector ==26714== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26714== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==26714== Command: ./TestCode2 ==26714== 
==26714== Invalid write of size 4 ==26714== at 0x400921: main (valgrindTestCode2.cpp:11) ==26714==  Address 0x5ab7c90 is 0 bytes after a block of size 16 alloc'd
==26714==    at 0x4C2DE96: malloc (vg_replace_malloc.c:309) ==26714==    by 0x4008F6: main (valgrindTestCode2.cpp:7) ==26714== 
==26714== Invalid read of size 4 ==26714== at 0x40092B: main (valgrindTestCode2.cpp:12) ==26714==  Address 0x5ab7c90 is 0 bytes after a block of size 16 alloc'd
==26714==    at 0x4C2DE96: malloc (vg_replace_malloc.c:309) ==26714==    by 0x4008F6: main (valgrindTestCode2.cpp:7) ==26714== the value of p is5 ==26714== 
==26714== HEAP SUMMARY: ==26714==     in use at exit: 72,720 bytes in 2 blocks ==26714==   total heap usage: 3 allocs, 1 frees, 73,744 bytes allocated ==26714== 
==26714== LEAK SUMMARY: ==26714==    definitely lost: 16 bytes in 1 blocks ==26714==    indirectly lost: 0 bytes in 0 blocks ==26714==      possibly lost: 0 bytes in 0 blocks ==26714==    still reachable: 72,704 bytes in 1 blocks ==26714==         suppressed: 0 bytes in 0 blocks ==26714== Rerun with --leak-check=full to see details of leaked memory ==26714== 
==26714== For lists of detected and suppressed errors, rerun with: -s ==26714== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

从上图结果中能够清晰的看到，提示出2个错误，提示信息分别为：“Invalid write of size 4”和“Invalid read of size 4”，而且提示了错误位置在源文件test2.cpp中的第11行和第12行。而且检测提示了：“total heap usage: 3 allocs, 1 frees, 73,744 bytes allocated”。有内存泄漏。

代码3. 内存覆盖

#include <stdio.h> #include <stdlib.h> #include <string.h>
int main() { char x[50]; int i; for(i=0;i<50;i++) x[i]=i+1; strncpy(x+20,x,20); strncpy(x+20,x,21); strncpy(x,x+20,20); strncpy(x,x+20,21); x[39]='\0'; strcpy(x,x+20); x[39]=39; x[40]='\0'; strcpy(x,x+20); return 0; } 在代码3中，strncpy(x+20,x,21),strncpy(x,x+20,21),strcpy(x,x+20)这三条语句，在进行字符串复制过程当中，复制与被复制的字符串空间存在交集。
经过复制操做，会改变初始字符串空间中的值。这就是内存覆盖的问题。在使用g++编译器对该程序编译并运行，结果以下： 
root@ranxf-TEST:/workdisk/testcode# g++ -g -o TestCode3 valgrindTestCode3.cpp root@ranxf-TEST:/workdisk/testcode# ./TestCode3 root@ranxf-TEST:/workdisk/testcode#

 

能够从上图中发现，程序在编译和运行过程当中并无报出任何错误，异常和警告。
但实际上存在内存覆盖的问题，当咱们不注意，再去使用原始字符串时，已经不是原来那个字符串了。
咱们使用valgrind对该程序进行检测，结果以下所示： root@ranxf-TEST:/workdisk/testcode# valgrind ./TestCode3 ==30101== Memcheck, a memory error detector ==30101== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==30101== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==30101== Command: ./TestCode3 ==30101== 
==30101== Source and destination overlap in strncpy(0x1fff0003c9, 0x1fff0003b5, 21) ==30101==    at 0x4C31706: __strncpy_sse2_unaligned (vg_replace_strmem.c:555) ==30101==    by 0x400648: main (valgrindTestCode3.cpp:11) ==30101== 
==30101== Source and destination overlap in strncpy(0x1fff0003b5, 0x1fff0003c9, 21) ==30101==    at 0x4C31706: __strncpy_sse2_unaligned (vg_replace_strmem.c:555) ==30101==    by 0x400680: main (valgrindTestCode3.cpp:13) ==30101== 
==30101== Source and destination overlap in strcpy(0x1fff0003a0, 0x1fff0003b4) ==30101==    at 0x4C311C6: strcpy (vg_replace_strmem.c:513) ==30101==    by 0x4006BA: main (valgrindTestCode3.cpp:18) ==30101== 
==30101== 
==30101== HEAP SUMMARY: ==30101==     in use at exit: 0 bytes in 0 blocks ==30101==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated ==30101== 
==30101== All heap blocks were freed -- no leaks are possible ==30101== 
==30101== For lists of detected and suppressed errors, rerun with: -s ==30101== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0)

提示三个错误，红色标识部分，并提示源文件中的错误行号11行，13行和18行

代码四、动态内存管理错误

 1 #include <iostream>
 2 #include <stdlib.h>
 3 int main()  4 {  5     int i;  6     char *p=(char *)malloc(10);  7     char *pt=p;  8     for(i=0;i<10;i++)  9  { 10         p[i]='z'; 11  } 12     delete p; 13     pt[1]='x'; 14     free(pt); 15     return 0; 16 }

在程序4中，使用malloc申请空间，使用delete释放空间，二者不匹配。使用malloc申请了10个字节的空间，只释放了一个字节空间。另外，对释放的空间仍然进行了读写操做。这些是典型的内存管理错误问题。在使用g++编译器对该程序编译并运行，结果以下 root@ranxf-TEST:/workdisk/testcode# g++ -g -o TestCode4 valgrindTestCode4.cpp root@ranxf-TEST:/workdisk/testcode# ./TestCode4 *** Error in `./TestCode4': double free or corruption (fasttop): 0x00000000023dfc20 ***
…… 已放弃 (核心已转储) 程序在运行中报出内存错误，但没有给出具体信息。咱们使用valgrind对该程序进行检测，结果以下所示 root@ranxf-TEST:/workdisk/testcode# valgrind ./TestCode4 ==31851== Memcheck, a memory error detector ==31851== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==31851== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==31851== Command: ./TestCode4 ==31851== 
==31851== Mismatched free() / delete / delete [] ==31851==    at 0x4C2F440: operator delete(void*) (vg_replace_malloc.c:586) ==31851==    by 0x4007E2: main (valgrindTestCode4.cpp:12) ==31851==  Address 0x5ab7c80 is 0 bytes inside a block of size 10 alloc'd
==31851==    at 0x4C2DE96: malloc (vg_replace_malloc.c:309) ==31851==    by 0x4007A7: main (valgrindTestCode4.cpp:6) ==31851== 
==31851== Invalid write of size 1
==31851==    at 0x4007EB: main (valgrindTestCode4.cpp:13) ==31851==  Address 0x5ab7c81 is 1 bytes inside a block of size 10 free'd
==31851==    at 0x4C2F440: operator delete(void*) (vg_replace_malloc.c:586) ==31851==    by 0x4007E2: main (valgrindTestCode4.cpp:12) ==31851==  Block was alloc'd at
==31851==    at 0x4C2DE96: malloc (vg_replace_malloc.c:309) ==31851==    by 0x4007A7: main (valgrindTestCode4.cpp:6) ==31851== 
==31851== Invalid free() / delete / delete[] / realloc() ==31851==    at 0x4C2EF90: free (vg_replace_malloc.c:540) ==31851==    by 0x4007F9: main (valgrindTestCode4.cpp:14) ==31851==  Address 0x5ab7c80 is 0 bytes inside a block of size 10 free'd
==31851==    at 0x4C2F440: operator delete(void*) (vg_replace_malloc.c:586) ==31851==    by 0x4007E2: main (valgrindTestCode4.cpp:12) ==31851==  Block was alloc'd at
==31851==    at 0x4C2DE96: malloc (vg_replace_malloc.c:309) ==31851==    by 0x4007A7: main (valgrindTestCode4.cpp:6) ==31851== 
==31851== 
==31851== HEAP SUMMARY: ==31851==     in use at exit: 72,704 bytes in 1 blocks ==31851==   total heap usage: 2 allocs, 2 frees, 72,714 bytes allocated ==31851== 
==31851== LEAK SUMMARY: ==31851==    definitely lost: 0 bytes in 0 blocks ==31851==    indirectly lost: 0 bytes in 0 blocks ==31851==      possibly lost: 0 bytes in 0 blocks ==31851==    still reachable: 72,704 bytes in 1 blocks ==31851==         suppressed: 0 bytes in 0 blocks ==31851== Rerun with --leak-check=full to see details of leaked memory ==31851== 
==31851== For lists of detected and suppressed errors, rerun with: -s ==31851== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 0 from 0) root@ranxf-TEST:/workdisk/testcode# 
从上图结果中能够清晰的看到，提示出的3个错误。
　　使用malloc申请空间，使用delete释放空间，二者不匹配问题：
　　　　“Mismatched free() / delete / delete []”;
　　使用malloc申请链10个字节的空间，只释放链一个字节空间：
　　　　“ Invalid free() / delete / delete[] / realloc()”;
　　对释放空间仍然进行读写操做：
　　　　“Invalid write of size 1”;

代码5：内存泄露

如下代码中分别存在makefile  test.cpp  tree.cpp  tree.h四个文件中

 1 /* makefile文件  2 
 3 test:test.o tree.o  4  g++ -g -o test test.o tree.o  5 tree.o:tree.cpp tree.h  6  g++ -g -c tree.cpp -o tree.o  7 test.o:test.cpp  8  g++ -g -c test.cpp -o test.o  9 
10 
/* tree.h文件 12 #ifndef _TREE_ 13 #define _TREE_ 14 typedef struct _node{ 15  struct _node *l; 16  struct _node *r; 17  char v; 18 }node; 19 node *mk(node *l,node *r,char val); 20 void nodefr(node *n); 21 #endif 22 
23 
/ * test.cpp文件 25 #include <iostream> 26 #include "tree.h" 27 int main() 28 { 29  node *tree1,*tree2,*tree3; 30  tree1=mk(mk(mk(0,0,'3'),0,'2'),0,'1'); 31  tree2=mk(0,mk(0,mk(0,0,'6'),'5'),'4'); 32  tree3=mk(mk(tree1,tree2,'8'),0,'7'); 33  return 0; 34 } 35 /* tree.cpp文件 37 
38 #include <stdlib.h> 39 #include "tree.h" 40 node *mk(node *l,node *r,char val) 41 { 42  node *f=(node *)malloc(sizeof(*f)); 43  f->l=l; 44  f->r=r; 45  f->v=val; 46  return f; 47 } 48 void nodefr(node *n) 49 { 50  if(n){ 51  nodefr(n->l); 52  nodefr(n->r); 53  free(n); 54  } 55 }

在程序5中，使用malloc申请空间后，没有使用free函数释放申请的内存地址形成内存泄漏。在使用g++编译器对该程序编译并运行，结果以下：

1 root@ranxf-TEST:/workdisk/testcode/valgrindTestCode5# ls 2 makefile test.cpp tree.cpp tree.h 3 root@ranxf-TEST:/workdisk/testcode/valgrindTestCode5# make 4 g++ -g -c test.cpp -o test.o 5 g++ -g -c tree.cpp -o tree.o 6 g++ -g -o test test.o tree.o 7 root@ranxf-TEST:/workdisk/testcode/valgrindTestCode5# 

root@ranxf-TEST:/workdisk/testcode/valgrindTestCode5# ls
makefile  test  test.cpp  test.o  tree.cpp  tree.h  tree.o
root@ranxf-TEST:/workdisk/testcode/valgrindTestCode5# ./test

能够从上图中发现，程序在编译和运行过程当中并无报出任何错误，异常和警告。但实际上存在内存泄漏的问题。咱们使用valgrind对该程序进行检测，结果以下所示：

 1 root@ranxf-TEST:/workdisk/testcode/valgrindTestCode5# valgrind ./test  2 ==6852== Memcheck, a memory error detector  3 ==6852== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
 4 ==6852== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info  5 ==6852== Command: ./test  6 ==6852== 
 7 ==6852== 
 8 ==6852== HEAP SUMMARY:  9 ==6852==     in use at exit: 72,896 bytes in 9 blocks 10 ==6852== total heap usage: 9 allocs, 0 frees, 72,896 bytes allocated 11 ==6852== 
12 ==6852== LEAK SUMMARY: 13 ==6852== definitely lost: 24 bytes in 1 blocks # 提示直接内存泄露 14 ==6852== indirectly lost: 168 bytes in 7 blocks # 提示间接内存泄露 15 ==6852==      possibly lost: 0 bytes in 0 blocks 16 ==6852==    still reachable: 72,704 bytes in 1 blocks 17 ==6852==         suppressed: 0 bytes in 0 blocks 18 ==6852== Rerun with --leak-check=full to see details of leaked memory 19 ==6852== 
20 ==6852== For lists of detected and suppressed errors, rerun with: -s 21 ==6852== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

由此看到：“total heap usage: 8 allocs, 0 frees, 96 bytes allocated”。

提示间接内存泄漏：“indirectly lost: 84 bytes in 7 blocks”;

提示直接内存泄漏：“definitely lost: 12 bytes in 1 blocks”

间接内存泄漏指：指向该内存的指针都位于内存泄漏处;

直接泄漏时指：没有任何指针指向该内存。

 

本篇中的代码样例及相关内容都来自于学习徐晓鑫女士编著的《后台开发核心技术与应用实践》所得，特此声明。

程序相关源码下载地址：https://github.com/XiaoYaoNet/Valgrind_Memset

参考文章：

　　valgrind 工具介绍和简单的使用

　　Valgrind工具以内存检测

　　valgrind 用法详见：http://blog.csdn.net/sduliulun/article/details/7732906