c++ char 内存泄漏与 valgrind 分析

Question

我有大约 350 行代码，我正在解析 xml 文件并使用 C++ 从中创建另外 2 个工作表。

添加最后 2 或 3 个函数后，我开始出现内存错误，

Signal: SIGSEGV (Segmentation fault)

删除它们并没有解决错误，所以我肯定编辑了其他内容。我在网上搜索并找到了有关 valgrind 的信息，它向我显示了我无法翻译的错误。

根据 valgrind 手册，我必须从下到上检查，所以按照最后一个，

==7276== 4,064 bytes in 1 blocks are definitely lost in loss record 52 of 54
==7276== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==7276== by 0x456BDD: ??? (in /usr/bin/g++-5)
==7276== by 0x4EC260D: _obstack_begin (obstack.c:176)
==7276== by 0x456FCE: ??? (in /usr/bin/g++-5)
==7276== by 0x43BA49: ??? (in /usr/bin/g++-5)
==7276== by 0x43BAC0: ??? (in /usr/bin/g++-5)
==7276== by 0x4E5A82F: (below main) (libc-start.c:291)

因为第 291 行是下面代码中的追加行，

if (vlan_ether)
sprintf(cConfStr, "**.Switch%ld.eth[%d].queue.VlanClassifier = true\n", srcindex + 1, portno);
else if (!vlan_ether)
sprintf(cConfStr, "**.Switch%ld.eth[%d].queue.etherType = false\n", srcindex + 1, portno);
else
cout << "Switch" << srcindex + 1 << "port# " << portno << " Classifier is not specified." << endl;
confStr.append(string(cConfStr));

删除上面的行没有做任何改变，而第 176 行是注释，所以我在犹豫 valgrind 是否显示错误行。

所以我不确定在我的问题中从代码中向您展示什么。我仍然确定它应该与我多次使用它们的字符串和字符使用有关。

char cNedStr[600];
char cConfStr[600];

sprintf(cConfStr, "%d ", intervalvector[q]);
confStr.append(string(cConfStr));

Valgrind 结果如下，

amr@amr-PC:~$ valgrind --leak-check=yes  g++ main.cpp pugixml.cpp headers.h -Wall -std=c++11

编辑：

amr@amr-PC:~/ClionProjects/converter$ valgrind ./a.out
==7624== Memcheck, a memory error detector
==7624== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==7624== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==7624== Command: ./a.out
==7624== Invalid free() / delete / delete[] / realloc()
==7624==    at 0x4C2F24B: operator delete(void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==7624==    by 0x5714FF7: __run_exit_handlers (exit.c:82)
==7624==    by 0x5715044: exit (exit.c:104)
==7624==    by 0x56FB836: (below main) (libc-start.c:325)
==7624==  Address 0x35663a37323a6536 is not stack'd, malloc'd or (recently) free'd
==7624== 
==7624== 
==7624== HEAP SUMMARY:
==7624==     in use at exit: 72,704 bytes in 1 blocks
==7624==   total heap usage: 525 allocs, 525 frees, 214,887 bytes allocated
==7624== 
==7624== LEAK SUMMARY:
==7624==    definitely lost: 0 bytes in 0 blocks
==7624==    indirectly lost: 0 bytes in 0 blocks
==7624==      possibly lost: 0 bytes in 0 blocks
==7624==    still reachable: 72,704 bytes in 1 blocks
==7624==         suppressed: 0 bytes in 0 blocks
==7624== Rerun with --leak-check=full to see details of leaked memory
==7624== 
==7624== For counts of detected and suppressed errors, rerun with: -v
==7624== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Answer 1

首先编译，不带头文件，（默认输出为a.out）：

g++ main.cpp pugixml.cpp -Wall -std=c++11

然后使用 valgrind 检查：

valgrind --leak-check=yes ./a.out

其他评论：

您可以考虑向 g++ 添加以下标志：

-Wextra（更多警告）
-迂腐（关闭扩展并生成更多警告）
-g（调试符号）
-O3（最大优化，不推荐调试！）

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