Valgrind 是一款 Linux下（支持 x86、x86_64和ppc32）程序的內存調試工具，它可以對編譯後的二進制程序進行內存使用監測（C語言中的malloc和free，以及C++中的new和delete），找出內存泄漏問題。
Valgrind 中包含的 Memcheck 工具可以檢查以下的程序錯誤：
1)使用未初始化的內存 (Use of uninitialised memory)
2)使用已經釋放了的內存 (Reading/writing memory after it has been free’d)
3)使用超過malloc分配的內存空間(Reading/writing off the end of malloc’d blocks)
4)對堆棧的非法訪問 (Reading/writing inappropriate areas on the stack)
5)申請的空間是否有釋放 (Memory leaks – where pointers to malloc’d blocks are lost forever)
malloc/free/new/delete
6)申請和釋放內存的匹配(Mismatched use of malloc/new/new [] vs free/delete/delete []) src和dst的重疊(Overlapping src and dst pointers in memcpy() and related functions) 重複free
1、編譯安裝 Valgrind：
wget http://valgrind.org/downloads/valgrind-3.4.1.tar.bz2
tar xvf valgrind-3.4.1.tar.bz2
cd valgrind-3.4.1/
./configure --prefix=/usr/local/webserver/valgrind
make
make install
2、使用示例：
2.1 對“ls”程序進程檢查，返回結果中的“definitely lost: 0 bytes in 0 blocks.”表示沒有內存泄漏。
[root@xoyo42 /]# /usr/local/webserver/valgrind/bin/valgrind --tool=memcheck --leak-check=full ls /
==1157== Memcheck, a memory error detector.
==1157== Copyright (C) 2002-2008, and GNU GPL'd, by Julian Seward et al.
==1157== Using LibVEX rev 1884, a library for dynamic binary translation.
==1157== Copyright (C) 2004-2008, and GNU GPL'd, by OpenWorks LLP. ==1157== Using valgrind-3.4.1, a dynamic binary instrumentation framework.
==1157== Copyright (C) 2000-2008, and GNU GPL'd, by Julian Seward et al.
==1157== For more details, rerun with: -v
==1157==bin data0 dev home lib64 media mnt opt root selinux sys tcsql.db.idx.pkey.dec ttserver.pid var boot data1 etc lib lost+found misc net proc sbin srv tcsql.db tmp usr
==1157== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 5 from 1) ==1157== malloc/free: in use at exit: 28,471 bytes in 36 blocks. ==1157== malloc/free: 166 allocs, 130 frees, 51,377 bytes allocated. ==1157== For counts of detected errors, rerun with: -v
==1157== searching for pointers to 36 not-freed blocks
==1157== checked 174,640 bytes.
==1157== LEAK SUMMARY:
==1157== definitely lost: 0 bytes in 0 blocks.
==1157== possibly lost: 0 bytes in 0 blocks.
==1157== still reachable: 28,471 bytes in 36 blocks.
==1157== suppressed: 0 bytes in 0 blocks.
==1157== Reachable blocks (those to which a pointer was found) are not shown. ==1157== To see them, rerun with: --leak-check=full --show-reachable=yes
2.2使用示例：對一個使用libevent庫編寫的“httptest”程序進程檢查，返回結果中的“definitely lost: 255 bytes in 5 blocks.”表示發生內存泄漏。
[root@xoyo42 tcsql-0.1]# /usr/local/webserver/valgrind/bin/valgrind --tool=memcheck --leak-check=full ./httptest
==1274== Memcheck, a memory error detector.
==1274== Copyright (C) 2002-2008, and GNU GPL'd, by Julian Seward et al.
==1274== Using LibVEX rev 1884, a library for dynamic binary translation.
==1274== Copyright (C) 2004-2008, and GNU GPL'd, by OpenWorks LLP.
==1274== Using valgrind-3.4.1, a dynamic binary instrumentation framework.
==1274== Copyright (C) 2000-2008, and GNU GPL'd, by Julian Seward et al.
==1274== For more details, rerun with: -v
==1274== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 1005 from 2)
==1274== malloc/free: in use at exit: 402,291 bytes in 74 blocks.
==1274== malloc/free: 15,939 allocs, 15,865 frees, 6,281,523 bytes allocated.
==1274== For counts of detected errors, rerun with: -v
==1274== searching for pointers to 74 not-freed blocks.
==1274== checked 682,468,160 bytes.
==1274== 255 bytes in 5 blocks are definitely lost in loss record 17 of 32
==1274== at 0x4A05FBB: malloc (vg_replace_malloc.c:207)
==1274== by 0x3C1D809BC6: evhttp_decode_uri (http.c:2105)
==1274== by 0x401C75: tcsql_handler (in /data0/tcsql/cankao/tcsql-0.1/tcsql)
==1274== by 0x3C1D80C88F: evhttp_get_body (http.c:1582)
==1274== by 0x3C1D8065F7: event_base_loop (event.c:392)
==1274== by 0x403E2F: main (in /data0/tcsql/cankao/tcsql-0.1/tcsql)
==1274== LEAK SUMMARY:
==1274== definitely lost: 255 bytes in 5 blocks.
==1274== possibly lost: 0 bytes in 0 blocks.
==1274== still reachable: 402,036 bytes in 69 blocks.
==1274== suppressed: 0 bytes in 0 blocks.
==1274== Reachable blocks (those to which a pointer was found) are not shown.
==1274== To see them, rerun with: --leak-check=full --show-reachable=yes
檢查httptest程序，發現有一處“char *decode_uri = evhttp_decode_uri(evhttp_request_uri(req));”中的“decode_uri”沒有被free，再程序處理完成後加上“free(decode_uri);”後，再使用Valgrind檢查，結果已經是“definitely lost: 0 bytes in 0 blocks.”。