c/c++的内存管理一直都是程序猿最头痛的事情，内存越界、数组越界、内存泄漏、内存溢出、野指针、空指针..., 随便一个问题都可能让程序崩溃。而且往往问题的源头都比较隐蔽，让人很难排查出问题的根源所在。

想要解决这个问题，还得从问题的根源入手。valgrind是一个强大的内存管理工具，常用来检测内存泄漏和内存的非法使用，用好了可以很好的从根源上解决c/c++内存管理的问题。

1.valgrind的主要功能

virgrind可以用来检测程序开发中的绝大多数内存，函数、缓存使用、多线程竞争访问内存、堆栈问题，是一个linux下功能非常强大内存检测工具。

1 valgrind工具

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

memcheck: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问题，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。下面将重点介绍此功能。

callgrind: 主要用来检查程序中函数调用过程中出现的问题。

cachegrind: 主要用来检查程序中缓存使用出现的问题。

helgrind: 主要用来检查多线程程序中出现的竞争问题。

massif: 主要用来检查程序中堆栈使用中出现的问题。

extension: 可以利用core提供的功能，自己编写特定的内存调试工具。

2 valgrind memcheck

2.1memcheck内存检测原理

valid-value表：

对于进程的整个地址空间中的每一个字节(byte)，都有与之对应的8个bits，对于CPU的每个寄存器，也有一个与之对应的bit向量。这些bits负责记录该字节或者寄存器值是否具有有效的、已经初始化的值。

valid-Address表：

对于进程整个地址空间中的一个字节(byte)，还有与之对应的1bit，负责记录该地址是否能够被读写。

内存检测原理：

当要读写内存中的某个字节时，首先检查这个字节对应的address bit。如果该address bit显示该位置是无效位置，memcheck则报告内存读写错误。valgrind内核相当于一个虚拟的CPU环境，当内存中的某个字节被加载到真实的CPU中时，该字节对应的value bit也被加载到虚拟的CPU环境中，一旦寄存器中的值，被用来产生内存地址，或者该值能够影响程序的输出，则mencheck会检查对应的value bits，如果该值尚未初始化，则会报告使用未初始化内存错误。

2.2 memcheck内存检测

2.2.1 准备源码

创建gdbmem.cpp源码文件，准备待检测的代码如下：

#include

#include

#include

#include

#include

#include

//memory access overflow

char* stringcopy(char* psrc)

{

int len = strlen(psrc) + 1;

char* pdst = (char*)malloc(len);//12

memset(pdst, 0, len * 2);//13

memcpy(pdst, psrc, len*2);//14

return pdst;

}

//array assess overflow

void printarray(int arry[], int arrysize)

{

int i = 0;

for(; i < arrysize; i++)

//for(i = arrysize-1; i >= 0; i--)

{

printf("arry[%d]:%d\n",i, arry[i]);

}

printf("arry[%d]:%d\n",i+1, arry[i+1]);//27

}

//main body

int main(int narg, const char** args)

{

char* pwildptr;

char* pstr = "this is a memory debug program!\n";

int array[10] = {1,2,3,4,5,6,7,8,9,10};

char* ptmp = stringcopy(pstr);//36

//memory leak

char* ptmp2 = (char*)malloc(100);//38

memset(ptmp2, 0, 100);

// memory write overflow

printf(ptmp);//41

// array tip assess overflow

printarray(array, 10);//43

free(ptmp);//44

printf("%p", pwildptr);//45

//wild ptr copy

memcpy(ptmp, ptmp2, 20);//47

printf(ptmp);//48

return 0;

}

2.2.2 编译源码：

$g++ -g -O0 -c gdbmem.cpp#-g：编译带调试信息的obj文件，-O0：不优化

$g++ -o gdbmem gdbmem.o

编译后将在当前目录下生成gdbmem可执行文件。

2.2.3 valgrind内存检测

valgring 对gdbmem进行内存检测

$ valgrind --tool=memcheck --leak-check=full --track-fds=yes ./gdbmem

==10668== Memcheck, a memory error detector

==10668== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.

==10668== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info

==10668== Command: ./gdbmem

==10668==

==10668== Invalid write of size 8

==10668== at 0x4C3453F: memset (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x40075D: stringcopy(char*) (gdbmem.cpp:13)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204060 is 32 bytes inside a block of size 33 alloc'd

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid write of size 1

==10668== at 0x4C34558: memset (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x40075D: stringcopy(char*) (gdbmem.cpp:13)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204080 is 16 bytes after a block of size 48 in arena "client"

==10668==

==10668== Invalid write of size 8

==10668== at 0x4C326CB: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400778: stringcopy(char*) (gdbmem.cpp:14)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204060 is 32 bytes inside a block of size 33 alloc'd

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid write of size 2

==10668== at 0x4C32723: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400778: stringcopy(char*) (gdbmem.cpp:14)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204080 is 16 bytes after a block of size 48 in arena "client"

==10668==

this is a memory debug program!

arry[0]:1

arry[1]:2

arry[2]:3

arry[3]:4

arry[4]:5

arry[5]:6

arry[6]:7

arry[7]:8

arry[8]:9

arry[9]:10

arry[11]:-623874025

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E8890E: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Use of uninitialised value of size 8

==10668== at 0x4E84711: _itoa_word (_itoa.c:180)

==10668== by 0x4E8812C: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E84718: _itoa_word (_itoa.c:180)

==10668== by 0x4E8812C: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E881AF: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E87C59: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E87CE2: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

main函数45行，memcpy(ptmp, ptmp2, 20);读取已经被释放的内存，导致memcheck报错。

==10668== Invalid write of size 8

==10668== at 0x4C326CB: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008FE: main (gdbmem.cpp:47)

==10668== Address 0x5204040 is 0 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid write of size 2

==10668== at 0x4C32723: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008FE: main (gdbmem.cpp:47)

==10668== Address 0x5204050 is 16 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid read of size 1

==10668== at 0x4ED0760: strchrnul (strchr.S:24)

==10668== by 0x4E87207: __find_specmb (printf-parse.h:108)

==10668== by 0x4E87207: vfprintf (vfprintf.c:1312)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x40090F: main (gdbmem.cpp:48)

==10668== Address 0x5204040 is 0 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid read of size 1

==10668== at 0x4E8741A: vfprintf (vfprintf.c:1324)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x40090F: main (gdbmem.cpp:48)

==10668== Address 0x5204040 is 0 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

0x40097d==10668==

==10668== FILE DESCRIPTORS: 3 open at exit.

==10668== Open file descriptor 2: /dev/pts/4

==10668==

==10668==

==10668== Open file descriptor 1: /dev/pts/4

==10668==

==10668==

==10668== Open file descriptor 0: /dev/pts/4

==10668==

==10668==

==10668==

==10668== HEAP SUMMARY:

==10668== in use at exit: 100 bytes in 1 blocks

==10668== total heap usage: 3 allocs, 2 frees, 1,157 bytes allocated

==10668==

==10668== 100 bytes in 1 blocks are definitely lost in loss record 1 of 1

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400888: main (gdbmem.cpp:38)

==10668==

==10668== LEAK SUMMARY:

==10668== definitely lost: 100 bytes in 1 blocks

==10668== indirectly lost: 0 bytes in 0 blocks

==10668== possibly lost: 0 bytes in 0 blocks

==10668== still reachable: 0 bytes in 0 blocks

==10668== suppressed: 0 bytes in 0 blocks

==10668==

==10668== For counts of detected and suppressed errors, rerun with: -v

==10668== Use --track-origins=yes to see where uninitialised values come from

==10668== ERROR SUMMARY: 37 errors from 15 contexts (suppressed: 0 from 0)

2.2.3 memcheck检测结果分析

memcheck的LEAK SUMMARY输出结果将内存泄漏分为以下几种情况：

definitely lost:明确地已经泄漏了，因为在程序运行完的时候，没有指针指向它, 指向它的指针在程序中丢失了

indirectly lost:间接丢失。当使用了含有指针成员的类或结构时可能会报这个错误。这类错误无需直接修复，他们总是与”definitely lost”一起出现，只要修复”definitely lost”即可。

possibly lost:发现了一个指向某块内存中部的指针，而不是指向内存块头部。这种指针一般是原先指向内存块头部，后来移动到了内存块的中部，还有可能该指针和该内存根本就没有关系，检测工具只是怀疑有内存泄漏。

still reachable:可以访问，未丢失但也未释放

suppressed:已被解决。出现了内存泄露但系统自动处理了。可以无视这类错误。

内存泄漏概述：

==10668== LEAK SUMMARY:

==10668== definitely lost: 100 bytes in 1 blocks

==10668== indirectly lost: 0 bytes in 0 blocks

==10668== possibly lost: 0 bytes in 0 blocks

==10668== still reachable: 0 bytes in 0 blocks

==10668== suppressed: 0 bytes in 0 blocks

此处只有100个字节的内存泄漏。

==10668== Invalid write of size 8

==10668== at 0x4C3453F: memset (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x40075D: stringcopy(char*) (gdbmem.cpp:13)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204060 is 32 bytes inside a block of size 33 alloc'd

根据错误提示，stringcopy 函数13行，即memset(pdst, 0, len 2);申请了len的数据长度，memset的时候却使用了2len的数据长度，内存写溢出了。

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid write of size 1

==10668== at 0x4C34558: memset (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x40075D: stringcopy(char*) (gdbmem.cpp:13)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204080 is 16 bytes after a block of size 48 in arena "client"

stringcopy 函数13行，即memset(pdst, 0, len2);申请了len的数据长度，memset的时候却使用了2len的数据长度，内存写溢出。相同语句的内存写溢出，却报了两个错误，原因笔者目前也还没有弄明白，如果有大虾指点，不胜感激。

==10668==

==10668== Invalid write of size 8

==10668== at 0x4C326CB: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400778: stringcopy(char*) (gdbmem.cpp:14)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204060 is 32 bytes inside a block of size 33 alloc'd

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid write of size 2

==10668== at 0x4C32723: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400778: stringcopy(char*) (gdbmem.cpp:14)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668== Address 0x5204080 is 16 bytes after a block of size 48 in arena "client"

stringcopy 函数13行，即memcpy(pdst, psrc, len2);申请了len的数据长度，memset的时候却使用了2len的数据长度，内存写溢出。

==10668==

this is a memory debug program!

arry[0]:1

arry[1]:2

arry[2]:3

arry[3]:4

arry[4]:5

arry[5]:6

arry[6]:7

arry[7]:8

arry[8]:9

arry[9]:10

arry[11]:-623874025

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E8890E: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Use of uninitialised value of size 8

==10668== at 0x4E84711: _itoa_word (_itoa.c:180)

==10668== by 0x4E8812C: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E84718: _itoa_word (_itoa.c:180)

==10668== by 0x4E8812C: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E881AF: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E87C59: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

==10668==

==10668== Conditional jump or move depends on uninitialised value(s)

==10668== at 0x4E87CE2: vfprintf (vfprintf.c:1631)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x4008E6: main (gdbmem.cpp:45)

main函数45行，printf("%p", pwildptr);读取未初始化的野指针

==10668==

==10668== Invalid write of size 8

==10668== at 0x4C326CB: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008FE: main (gdbmem.cpp:47)

==10668== Address 0x5204040 is 0 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid write of size 2

==10668== at 0x4C32723: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008FE: main (gdbmem.cpp:47)

==10668== Address 0x5204050 is 16 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

main函数47行，memcpy(ptmp, ptmp2, 20);写入已经释放的内存

==10668==

==10668== Invalid read of size 1

==10668== at 0x4ED0760: strchrnul (strchr.S:24)

==10668== by 0x4E87207: __find_specmb (printf-parse.h:108)

==10668== by 0x4E87207: vfprintf (vfprintf.c:1312)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x40090F: main (gdbmem.cpp:48)

==10668== Address 0x5204040 is 0 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

==10668==

==10668== Invalid read of size 1

==10668== at 0x4E8741A: vfprintf (vfprintf.c:1324)

==10668== by 0x4E8F898: printf (printf.c:33)

==10668== by 0x40090F: main (gdbmem.cpp:48)

==10668== Address 0x5204040 is 0 bytes inside a block of size 33 free'd

==10668== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x4008D0: main (gdbmem.cpp:44)

==10668== Block was alloc'd at

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400740: stringcopy(char*) (gdbmem.cpp:12)

==10668== by 0x40087A: main (gdbmem.cpp:36)

main函数47行，printf(ptmp);写入已经释放的内存

0x40097d==10668==

==10668== FILE DESCRIPTORS: 3 open at exit.

==10668== Open file descriptor 2: /dev/pts/4

==10668==

==10668==

==10668== Open file descriptor 1: /dev/pts/4

==10668==

==10668==

==10668== Open file descriptor 0: /dev/pts/4

==10668==

linux为了实现一切皆文件的设计哲学，不仅将数据抽象成了文件，也将一切操作和资源抽象成了文件，比如说硬件设备，socket，磁盘，进程，线程等。

这样的设计将系统的所有动作都统一起来，实现了对系统的原子化操作，大大降低了维护和操作的难度。

设备描述符，就是描述该文件数据设备的唯一标示，不同类型的文件，文件描述符也不一样，如下所示：

==10668==

==10668==

==10668== HEAP SUMMARY:

==10668== in use at exit: 100 bytes in 1 blocks

==10668== total heap usage: 3 allocs, 2 frees, 1,157 bytes allocated

==10668==

==10668== 100 bytes in 1 blocks are definitely lost in loss record 1 of 1

==10668== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==10668== by 0x400888: main (gdbmem.cpp:38)

==10668==

内存泄漏概述，3次内存分配，两次释放。已经有100个字节的内存已经确定泄漏。泄漏的内存分配于38行，charptmp2 = (char)malloc(100);至此，内存泄漏检测完毕。

valgrind内存检测解析

valgrind对内存读写溢出，读取未初始化的变量、指针、内存能够很好的检测到，但是对于数组越界却无法检测，这是因为memcheck并不对stack和全局数组进行越界检查，所以无法检测出printarray中的内存访问越界。

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