Linux C/C++內存泄漏檢測工具:Valgrind

Valgrind 是一款 Linux下(支持 x86、x86_64和ppc32)程序的內存調試工具，它可以對編譯后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：

　　使用未初始化的內存 (Use of uninitialised memory)
　　使用已經釋放了的內存 (Reading/writing memory after it has been free’d)
　　使用超過malloc分配的內存空間(Reading/writing off the end of malloc’d blocks)
　　對堆棧的非法訪問 (Reading/writing inappropriate areas on the stack)
　　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)
　　重復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：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==?
==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==?
==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

　　3、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==?
==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==?
==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==?
==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，再程序處理完成后加上“free(decode_uri);”后，再使用Valgrind檢查，結果已經是“definitely lost: 0 bytes in 0 blocks.”。

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