valgrind 性能测试工具学习使用
一、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。它可以检测许多与C和C ++程序中常见的内存相关的错误,这些错误可能导致崩溃和不可预测的行为。
标准配置提供了许多有用的工具:
- Memcheck是一个内存错误检测器。可以帮助你使程序更加正确。——这是valgrind应用最广泛的工具,一个重量级的内存检查器,能够发现开发中绝大多数内存错误使用情况,比如: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。
- Cachegrind是一个缓存和分支预测分析器。可以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。
- 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中出现的问题。
- Helgrind是一个线程错误检测器。可以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。
- DRD也是线程错误检测器。他与Helgrind类似,但是用不同的分析技术,因此可能会发现不同的问题。
- Massif时一个堆分析器。可以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。
- DHAT时一种不同类型的对分析器。可以帮助了解块寿命,块利用率和效率低下的问题。
- SGcheck时一种实验工具,可以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无法解决的问题,反之亦然。
- 小工具: Lackey是一个示例工具,用于说明一些仪器基础知识和
- 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,只需正常运行即可。它主要用于Valgrind的开发人员进行调试和回归测试。尽管如此,您可以使用Nulgrind运行程序。它们的运行速度比正常情况慢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
). - extension ------> 可以利用core提供的功能,自己编写特定的内存调试工具(不在我学习的范围中)
二、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,然后编译
# 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)
三、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)
四、Valgrind 命令参数介绍
用法: valgrind [options] prog-and-args
[options]: 常用选项,适用于所有Valgrind工具
最常用的命令格式:
valgrind --tool=memcheck --leak-check=full ./test
-h –help 显示帮助信息。(除了以下参数,可用帮助-h查看更多信息) --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
还是在-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 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]
五、测试案例介绍
(一)测试demo
/workdisk# vim /workdisk/testcode/testValgrind.cc # 在该路径下生成喊以下内容的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链接文件同名,否则会生成相应可执行文件且覆盖原编译或链接文件),如果不使用-o选项,则会生成默认可执行文件a.out。
-c:只编译不链接,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
如果valgrind添加了环境变量,输入命令可以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)中肯定丢失 ==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 肯定泄露: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 仍然可以访问: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,请使用以下项重新运行:--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重新运行。 ==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,一种是肯定的内存泄露(definitely lost),一种可能的内存泄露(possibly lost);
Definitely lost 是指已经不能够访问这块内存;
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能够访问某块内存,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,但是在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,结果如下:
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中并没有报出任何错误,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。我们使用valgrind对该程序进行检测,结果如下所示:
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) (此处要求我们在进行g++编译时添加-g参数,不然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
从上图结果中可以清晰的看到,提示出1个错误,提示信息为:“Conditional jump or move depends on uninitialised value(s)”,并且提示了错误位置在源文件test1.cpp中的第10行(此处要求我们在进行g++编译时添加-g参数,不然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。
之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没有申请。所以,p指针变成链野指针。
程序中并且又对p的地址空间进行写操作。这就造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,结果如下: 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)
从上图结果中可以清晰的看到,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”,并且提示了错误位置在源文件test2.cpp中的第11行和第12行。并且检测提示了:“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中,复制与被复制的字符串空间存在交集。
通过复制操作,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,结果如下: root@ranxf-TEST:/workdisk/testcode# g++ -g -o TestCode3 valgrindTestCode3.cpp root@ranxf-TEST:/workdisk/testcode# ./TestCode3 root@ranxf-TEST:/workdisk/testcode#
可以从上图中发现,程序在编译和运行过程中并没有报出任何错误,异常和警告。
但实际上存在内存覆盖的问题,当我们不注意,再去使用原始字符串时,已经不是原来那个字符串了。
我们使用valgrind对该程序进行检测,结果如下所示: 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4、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,两者不匹配。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作。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,结果如下 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。我们使用valgrind对该程序进行检测,结果如下所示 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#
从上图结果中可以清晰的看到,提示出的3个错误。
使用malloc申请空间,使用delete释放空间,两者不匹配问题:
“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作:
“Invalid write of size 1”;
代码5:内存泄露
以下代码中分别存在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造成内存泄漏。在使用g++编译器对该程序编译并运行,结果如下:
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
可以从上图中发现,程序在编译和运行过程中并没有报出任何错误,异常和警告。但实际上存在内存泄漏的问题。我们使用valgrind对该程序进行检测,结果如下所示:
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 用法详见:http://blog.csdn.net/sduliulun/article/details/7732906